T- _._.... ~ I- l '

THE HEALTH HAZARDS OF RADIOFREQUENCY, MICROWAVE, AND LASER RADIATION

by

Paul Brodeur

'',

..

- ·TABLE OF CONTENTS

Section A - MICROWAVE/RADIOFREQUENCY RADIATION______

Part I INTRODUCTION

Part II WHAT IS RADIOFREQUENCY AND MICROWAVE­ RADIATION?

- Part III THE HISTORY OF RADIO WAVES -AND MICROWAVES

Part IV THE BIOLOGICAL EFFECTS OF RADIO WAVES ... -·., f \_ AND MICROWAVES

Part V THE MICROWAVE COVER-UP AND ITS CONSEQUENCES

Part VI PREVENTING HARMFUL RF/MW EXPOSURE

Section --B - LASERS

Appendixes

Part I

INTRODUCTION

Human beings are constantly surrounded and penetrated-

- - -- ~ by various kinds of electromagnetic radiation flowing from= - - the· sun and the stars. Such radiation, which includes light·, is :relatively weak and entirely natural. In less than half- - a century, however, this situation, which has existed since the beginning of mankind, has changed drastically.· In today'~ electronic world, ma.n's inventions have increased the radia.= tion levels on earth tens of millions of times. By now, almost everybody· is aware that high-frequency electromagnetic radiation, such as X-rays and gamma rays, can cause radiation sickness and cancer. At the ·other end of the electromagnetic spectrum, however, there are radia­ tions of _lower frequency, called radio waves and microwaves. These waves· either pass through or penetrate deeply into human- tissue. Until recently, they were c·onsi-dered to "u~ relatively harmless. Radiofrequency (RF) and microwave (MW) radi-ation is beamed into the workplace environment from a wide variety of industrial devices, such as radiofrequency sealers, heaters, and welders. It is beamed into the general environ= ment from television, radio, and radar transmitters; from telephone relay systems, orbiting satellites, and from - 2 -

microwave ovens, diathermy machines, burglar alarms, Citizen­ Band radios, and countless other civilian uses, as well as from a vast arsenal of military weapons. The Department of Defense (DOD) is by far the largest single user of RF/MF equipment. The DOD possessses 20 million radar and microwave devices. In addition, there are 30 million Citizen-Band radios, 10 million microwave ovens,·2so,ooo microwave communication towers, 15,000 shortwave radio trans­ mitters, and 15,000 medical diathermy units. Many environmentalists claim that the skies of the nation are being saturated with radiation emanating from such devices. Some people call it electronic smog. The situation is extremely worrisome in the workplace. Here, the use of radiofrequency and microwave radiation has achieved staggering proportions. The National Institute for Occupational Safety and Health (NIOSH) estimates that there are now over 35 million RF sources in use in industry. NIOSH also estimates that up to 21 million workers are poten­ tially exposed to RF/MW radiation on the job. Some of the workplace applications of RF/MW radiation are: * Agriculture (treatment of seeds, destruction of insects, drying of grain.) * Automotive (heat-sealing body interiors and up­ holstery covers.) * Chemical (curing of epoxy resins.) = 3 -

* Food products (melting chocolate and.thawing baked-­ goods; drying, heating, and sterilization.) * Forest products (hardwood and paper drying; destruc=

tion of fungus and woodworm.) * Furniture-woodworking ( lumber and plywood- bonding;· lamination skis, doors, and fiberboard.) * Plastic products (heat-sealing various plastic materials including plasticized polyvinrl chloride, polyurethane foam, etc.) - * Rubber products (preheating and drying latex, rubber tires.) * Textile (drying rayon and cloth yarns and webs.) * Telephonic communications systems.

The Human Factor

Nature has not prepared us for the invisible assault of radiowaves and microwaves. Radar techni.ci.a.ns and ele.c.,. tronics workers exposed to such radiation may be developing cataracts, blood disorders, and cardiovascular problems. Workers using RF sealers and heaters are experiencing·eye problems, skin rashes, aching of bones, and loss of hair. Other workers exposed to B:F/MJI radiation are suffering from altered behavior, dizziness, headaches, irritabilty, loss of judgement, and other disorders of the central nervous system. - 4 -

Animal fetuses irradiated with microwaves develop birth defects. Microwave and radiofrequency radiation may also cause genetic problems in humans by damaging chromosomes and sperm .. And there is mounting evidence linking such radiation to the development of cancer. Scientists in Russia and in other Eastern European nations have warned about the.hazards associated with RF/MW radiation for more than twenty years. In the U.S.S.R., the permissable level for occupational exposure to radiofrequency and microwave radiation is 1000 times less than ours in the United States. In recent years, American scientists have become increasingly aware of the potential threat to human health posed by RF/MW radiation. As early as 1971, the Electro­ magnetic Radiation Management Advisory Council (ERMAC) wrote a report for.the President stating that microwave power levels."in and around American cities, airports, military installations, and tracking centers, ships and pleasure craft, industry and homes may already be bio­ logically significant." The Council went on to warn that "the consequences of undervaluing or misjudging the bio­ logical effects of long-term; low-level exposure could become a critical problem for the public health, especially if genetic effects are involved." In spite of this warning, however, little has been - 5 -

done to prevent unecessary exposure to radiofrequency and microwave radiation in the UoSoAo Today, the Department of Laborvs Occupation-al Sa:Cety and Health Administration (OSHA) is finally beginning to . -·recognize operations which cause high~level exposures to B:F/MW radiation, which are commonplace in American industryo This manual is intended to inform workers about the nature of the microwave hazard, what is known about the biological ef f~ts of RF /MW radiation, and what can be done to prevent exposure and protect human healtho Unfortunately, it must also stand as a reminder of the necessity for far swifter and more effective publ::tc control of occupational and environmental health hazards. - 6 -

Part II

WHAT IS RADIOFRE.QUENCY AND MICROWAVE· ~ADI'AT-ION

Like all electromagnetic radiation, radio waves and microwaves travel at the speed of light--approximately 186,000 miles per second. And, like all electromagnetic radiation, they are produced when an electric charge sets off waves, or ripples, of electric and magnetic energy, which radiate through space. Waves of electromagnetic energy occur in much the same way that a rock thrown into a pond sets off waves that ripple the surface of the water. Except f·or visible light, electromagnetic radiation travels in the form of invisible waves. These waves move in a similar manner as water waves. Electromagnetic waves are measured by their frequency--the nunber of times they go up and down per second. (Frequency used to be expressed as cycles per second; today, it is expressed as "hertz" which means cycles per second.) Electromagnetic waves are also measured by their wavelength--the distance from the peak of one wave to the peak of the next. Scientists studying the properties of the various kinds of electromagnetic waves customarily arrange them according to frequency and wavelength in what is called the electromagnetic spectrum. At one end of this spectrum - ·------~

- 7 -

are long waves with low frequencyo At the other endare

·--short waves with high frequency o ---- The longest waves in the electromagnetic spectrum are radio waveso Some of these stretch for thousands of miles and vibrate at a frequency of about ten hertz (lOHz). This

is called Extra Low Frequency (ELF) radiationo In general, -however, the frequency range of the radio-wave portion of the electromagnetic spectrum is considered to run from o5 million hertz (0.5MHz) to 300 million hertz (300 MHz)o This portion of the spectrum is used for standard radio broadcasting, Citizen-Band radios, FM radio broadcasting,

VHF television, industrial sealers and heaters, and certain kinds of radaro The microwave portion of the electromagnetic spectrum ranges from 300 MHz to 300 billion hertz (300 GHz)o This portion of the spectrum is used for UHF television, micro­ wave ovens, satellite-to-earth communication, and most radaro As we continue up the electromagnetic spectrum, we find that the frequencies of the various radiations become higher, and that the!r wavelengths are shorter. After micro­ waves, for example, comes infrared radiation which can oscillate up to 100 trillion times a secondo Visible light. ' is next on the scale, and of course, it vibrates even faster. Then, in order, come ultraviolet radiation, X-rays, and gamma rays. - 8 -

Gamma rays are extremely high-frequency radiation. They are emitted by radioactive substances such as_radium and uranium, and during atomic and nuclear explosions. The frequency of gamma rays is measured in millions of trillions of hertz.

How Do Radio Waves, Microwaves, and Other Electromagnetic Radiation Affect the Human B"ody?

The various radiations in the electromagnetic spectrum affect the body in different ways. Some of these effects depend upon frequency. For example, because of their extreme high frequen­ cies, X-rays and gamma rays possess tremendous energy and enormous penetrating power. In fact, these rays vibrate so quickly that the material through which they pass breaks up into electrically charged particles called ions. This is why X-rays and gamma rays are known as ionizing radiation. The ions released by X-rays and gamma rays are capable of inflicting terrible damage upon human tissue. This is why so many residents of Nevada and Utah, who lived down­ wind of the early nuclear testing sites, have developed leukemia. It also explains why the National Cancer Insti­ tute has issued warnings against unnecessary exposure to X-rays. = 9 =

All of the lower frequencies in the electromagnetic spectrum==ultraviolet, visible light, infrared, microwaves, · and radio waves=-are referred to as non-ionizing. radiation. This -means that they do not have the capac·i.ty to.. create ions .·

tne way X=rays and gamma rays do 11 and that they. -do-not

~ ·destroy the cells in human tissue the way ionizing-iuadia.- · tion does. However, this does not mean that non-ionizing radiation is not dangerous to human health. For example, it is well known that ultraviolet radiation can cause skin cancer. - ·The fact is, scientists do not fully understand how non-ionizing radiation such as ultraviolet.:..,. __micro]lla.ves_. ______and radiowaves affect the body. This lack of understanding is not unusual. For example, scientists do not fully under= stand wwasbestos causes cancer. Yet the government esti­

mates that hundreds of thousands of American workers are doomed to die of cancer caused by asbest·os.

One thing that has been known for a long time about radio waves and microwaves is that they can caus-e hec:1,l:ing in tissue.

How Do Radio Waves and Microwaves Heat Tissue?

Extra Low Frequency radio waves tend to pass through the body. Higher frequency radiowaves and microwaves are - 10 -

absorbed by the body tissues. Such radiation causes heat= ing in the following manner: When rrF/MW radiattcu.penetrates into tissue, it excites the molecules of water that are present in all tissue. The excited molecules move about and collide with one another. These collisions produce friction, and the friction pro­ duces heat. If the B:F/M:W radiation is powerful enough, it can not only heat t~ssue, but cook it. This is, of course, what happens to a roast of beef in a microwave oven.

How Is The Power of Radio Waves and Microwaves Measured?

The power of a radio wave or a microwave source can be measured by the intensity of its beam. This.intensity is measurett in terms of power density. Power density is the a.mount of energy carried by a radio wave or a microwave as it flows each second through a square measure of space. The energy carried by a radio or microwave beam is expressed in terms of watts (W), milliwatts (mW), or micro­ watts (uW). A milliwatt is 1/1000 of a watt, and a micro- ' watt is one millionth of a watt and 1/100 of a milliwatt. The square measure of space through which the energy flows is expressed as a centimeter squared ~m2.) This is an area approximately one/half the size of a 15~ postage stamp. - 11 -

The power density that cooks food inside a microwave ·- ·oven is between 500 and 1000 milliwatts per centimeter squared (500-1000 mW/cm2).

The power density of the sun's energy .. on the surf ace .. - of the earth at the equator is about· 100 miJ.,liwatts. per. . . centimeter squared (100 mW/cm.2). The present American guideline for occupational ex­ posure to RF/MW radiation is ten milliwatts per centimeter squared (10 m~/cm2). The standard for occupational exposure to RF/~_radia­ tion in the Soviet Union is one thousand times less. It is ten microwatts per centimeter squared (10uW/cm2).

The history and adequacy of the various P.:F/MW exposure standards will be discussed later.

Can Low-Level Radio Waves and Microwaves Affect Human Health?

A great debate is now raging in the American scientific community about whether RF/MW levels too low to cause measur­ able heating of tissue can result in harmful biological effects. Much of the debate centers on the fact that ivnontherrnal" effects cannot be understood on a theoretical level. Scientists in the U.S.S.R., Poland, Czechoslovakia, China, Canada and Sweden are not so concerned with theo­ retical considerations. Their studies show that nonthermal - 12 -

biological effects do occur. The occupational exposure standards in all of these countries reflect the results of these studies. Mounting laboratory evidence in the U.S. now indicates that biological effects exist far below the present occu­ pational guideline of 10mW/cm2. The wide variety of thermal and nonthermal effects of RF/MW radiation will be discussed elsewhere in this manual. = 13 -

Part III

-~-=--THE HISTORY OF RADIO WAVES- -AND MICROWAVES

- Electromagnetic waves were first shown to exist-in

- 1888, when a German physicist named Heinrich Hertz pro~- . duced a spark a.cross a spark gap with a powerful electric charge, and detected it instantly a.cross the room. In 1894, an English physicist named Sir Oliver Joseph Lodge used electromagnetic waves to transmit telegraph signals over a distance of half a mile. This invention became known as wireless telegraphy. Guglielmo Marconi, the Italian electrical engineer, invented long-distance wireless telegraphy, and pioneered -its use for ship-to-sh~re communication. First, he sent messages in Morse code across the English Channel. Then, in 1901, he transmitted in Morse Code a.cross.the Atlantic Ocean from England to Newfoundland. By 1915, thanks to the invention of the rad:i.(' frequency· amplifier-and-generator by an American named Lee De Forest, spoken words were transmitted from Long Island, N.Y., to Wilmington, Delaware, a distance of 214 miles. By the end of the year, speech was transmitted over a distance of 5,000 miles. The Age of Radio was at band. In 1920, the first commercial radio station began transmitting in Pittsburgh, Pa. - 14 -

Radio broadcasting had been predicted as early as 1893 by Nikola Tesla, a brilliant electrical engineer, who had emigrated to the United States from Croatia. Tesla invented the Tesla transformer, the induction motor, and the alternating-current system of electricity. In --1895, his alternating-current system was used to generate hydroelectric power at Niagara Falls. This is considered to be one of the most significant feats in all of engi­ neering history. In many ways, the inventive genius of Tesla was even greater than that of Thomas Edison, who invented the elec­ tric light bulb, and who is often thought of as the father of electricity. While living in Colorao, before the turn of the century, Tesla used a giant· electromagnetic gen­ erator to produce man-made lightning. In 1898, he demon­ strated remote-control radio guidance system for ships. I_n 1900, he predicted that radio waves would one day be used to detect moving objects, such as ships at sea. During the 1930s Tesla's prediction came true with the invention of radar, which stands for radio detection and !_anging. Radar is possible because microwaves are reflected by electrical conductors such as metal and raindrops. Radar works by aiming a powerful beam of microwaves in short bursts, or pulses, at a metal target such as an airplane. It then picks up the microwaves reflected by the target, and measures the distance to the target on the basis. of elapsed time. In 1934, when he was 78 years old, Tesla predicted that electromagnetic ·radiation would one day- be used t.o~ _ knock enemy airplanes out of the sky. Today, the Department of Defense is developi-ng laser· beams and other electromagnetic radiation weapons capable of destroying enemy missiles and satellites.

As early as 1980, Tesla performed experiments showing that tissues became heated when subjected to high-frequency radio waves. However, credit for pioneering the medical uses of radio waves belongs to·aFrench physician named Jacques Arsene d'Arsonval. He invented a treatment called

11 diathermy, which means "heating through. _ By 1900, _radio_ diathermy machines were being used to stim~iate blood flow and to treat a wide variety of aches and pains.

With the advent of RF technology, diathermy machines were improved. Today, there are more than 15 ,_ooo diathermy ma.ch~nes in use in the United States. An estimated. _two million Americans are given heat treatments_ each year

with microwave radiation for such ailments as arthritis 1 _ bursitis, muscle-soreness, sprains, and congested sinuses. - 16 -

Early Microwave Technology

During the 1920s, static was the great obstacle to the rapid development of radio. By the end of the decade, American scientists came to realize that radio waves of long wavelength and low frequency were extremely vulner-

- able to statico Meanwhile, Marconi was pioneering the use of sho-rter and shorter radio waves for long-distance communication and had established shortwave telegraph links between Britain and Canada. This marked an important turning point in the history of telecommunications. The entire trend since then has been to develop equipment capable of generating higher frequency radio waves, whose capacity for carrying messages has proved to be greater and greater. In 1933, French and English engineers set up a radio­ communication system across the English Channel using- waves with the then unheard of high frequency of 1,750 million hertz per second ( 1, 750 MHz. ) They called this new system Microray Wireless. The first half of the name caught on. Within a few years, all the ultrahigh, superhigh, and extremely high frequencies-­ those frequencies lying just below the infrared region of the electromagnetic spectrum--were called microwaves. The Advent of Radar

- During the Battle of Britain, th~ English land-based microwave radar sy~tem was able to detect G~rman bombers and measure how far away they were with great accura~y. : -- It -was soon realized, however, that mic;:rowaves of _ . much shorter length and ~igher frequency wo~ld be necessary for radar equipment light and compact enough to be carried in planes. Such radar was needed in order to carry out precision bombing through cloud cover. Compact radar soon became available owing to-improve­ ments made by British engineers in the pulsed magnetron-­ a device capable of geRerating microwaves that vibrate at~ frequency of 3000 MHz .

.Sy tlie end of the war, magnetrons were deve.loped that could generate microwaves with a frequency of 48,000 MHz.

Modern Mi·crowave Technology

In 1947, the Bell Telephone Company established a microwave radiotelephone system between Boston and New Yor.k. Today, virtually all long distance telephone mes­ sages are carried by such microwave links. At about the same time, television was beginning to be developed for public use. At first, television pro­ grams were broadcast from RF microwave generators on tall - 18 -

buildings and towers. Today, TV images are beamed from broadcast satellites in space. In 1945, the Raytheon Company filed a patent pro­ posing that microwaves be used to cook food. The-- idea for thi.s occurred to Dr. Percy Spencer, when.,_ after fee-ling_ -the warmth of a microwave beam on his hand, he used the­ beam to pop some popcorn. In the Electronic Age in which we live, the possi­ bilities for the future application of RF/microwave radia­ tion appear limitless. Microwave communication satellites will soon be able to handle 70,000 conversations at once. There is presently a scheme to place solar power satellite stations into orbit. These· staions will capture the sun's energy, convert it into microwaves, and beam the microwaves to earth, where they will be converted into electric current. So much for the wonders of radiofrequency and micro~ wave technology. What are their effects on human health? Part IV

--THE ~----BIOLOGICAL EFFECTS -OF RADIO WAVES AND MICROWAVES

Early Studies in the U.S.

When Microwave technology was being developed in the 1920s and 1930s, almost no one believed that this type of electromagnetic radiation would prove to have harmful effects on health. In genera~, doctors and scientists were convinced that the only· biological effect of radio waves and microwaves was the heating of tissue. During the early part of World War II, however, rumors about the sterilizing effects of radar beams spread like wildfire in the U.S. Navy. Some Navy radarmen were even known to charge a fee for giving microwave "treat­ mentsn to shipmates going ashore on liberty. At the same _time, many sailors believed that radar could cause their hair to fall out. In the spring of 1942, the Navy gave health examina­ tions to some of its civiiian radar workers to see if the stories about these effects were true. The study found no sign of sterility or baldness. However, many of the radar workers complained of headaches, eye pain, and a flushed feeling in the face when they were exposed to '• ...... microwaves emanating from radar antennas. These symptoms were dismissed by the Navy doctors, who did not consider them to be important. - - -After the war, scientists in the Uo S .__ -_ began to study __ -____ ·-·_ the heating effects of heavy doses of microwave radiation

. . on test animals. When they irradiated the eyes- of rabbi ts and dogs with microwave power densities of up to 3,000 mW/cm2 , - they found that ten-minute exposures could produce thermal 1------cat-aracts--a coagulation of the lens of the eye that can result in blindness. (Remember that the power density that cooks food in a microwavw oven is between 500 and 1000 mW/cm2 ;j What these scientists were doing, therefore, amounted to cooking the eyeball, which, like the white of an egg in a frying pan, or in a pot of boiling water, coagulates and becomes irreversibly opaque when it is sub­ jected to sufficient he~to Other investigators at this time were able to produce severe testicular damage in rats and dogs with high doses of microwave radiationo Circulating blood acts as a coolant

±n---t-h-e--b-o-dy. The eyes and testicles are especially vul- nerable to microwave heating because they are not ·well equip­ ped with blood vessels and have poor blood circulation. Still other scientists were able to kill dogs through overheating (hyperthermia) by exposing them for 30 minutes to 2 microwave beams with a power density of only 40 mW/cm2! ...-----~------~~,;;,--;,,;----

Events in the 1950s

In 1951, a microwave technician employed by the Sandii Corporation, near Albuqurque, New Mexico, developed cataracts in botb eyes after working for only eleven months with an

~ -e,rpe_rim_ental microwave generator. Doctors estimated that he had been exposed to a microwave power density of about 100 mW/cm2. When news of this case got out, some people in the medical profession began to worry that other parts of the body with, relatively poor blood circulation, such as the cavities of the gastrointestinal tract, the gall bladder,

I and the urinary tract, might also prove vulnerable to microwave.damage. In 1953, a California surgeon, Dr. John T. McLaughlin, sent the military a report warning that excessive exposure to microwave radiation could cause internal bleeding, leukemia, ca.tatacts, headaches, brain tumors, heart con= d~tions, and jaundice. In 1954, Dr. McLauhglin treated a 42-year=old Hughes Aircraft Company radar repairman, who died a few days after he had unwittingly stood in the main beam of a radar transmitter. Dr. McLaughlin later published an article in which he declared that the man's bowels had been cooked, and that his patient had "died from tissue destruction caused by absorption of microwave energy."

i ------__ j - 22 -

The Hughes Air Craft Company tried unsuccessfully to obtain a court injunction against publication of this article. Dr. McLaughlin's observations should have triggered a -large-scale investigation of the health effects of micro­ wave radiation among people working with radar in the armed services and the electronics industry. This did not happen. One of the reasons often given was that such a-stucry-mi-gnt·· have "compromised security regulations." -----· ----·-·-- Later in 1954, a study of radar workers at the Lock­ heed Aircraft Corporation, in Burbank, California, showed significant changes in white-blood cell counts and a high incidence of eye disease among the men who were most heavily exposed to microwaves. The Lockheed workers also complained of buzzing vibrations in the head and ears, as well as fatigue, headache, and aching eyeballs. These data and symptoms were generally ignored by people in the medical community. In 1955, repesentatives of the medical profession, the armed services, and the electronics industry met at the Mayo Clinic, in Rochester, Minnesota, and decided that human oeings could be exposed to a microwave power density of ten milliwatts per centimeter squared (10 mW/cm2) with­ out harmful effects. The 10 mW/cm2 exposure guideline was first proposed in 1953 by Professor Herman P. Schwan, a professor of electrical engineering at the University of Pennsylvania. - 23 -

·Professor Schwan arrived at this recommendation on theo­ retical grounds. He based it upon the fact that heat _is dissipated from the surface of the human body at a certain rate, and on the assumption that the body could .. t_olerate the additional heat load caused by exposures of 10 mW/cm2 - without harmful effects. By the end of the 1950s, the 10 mW/cm2_guideline was adopted by the Army, the Navy, the Air Force, and by the leading electron±cs corporations. It is still in effect today. ·

Early RF/MW Studies in the Soviet Union

As early as 1933, scientists in the U.S.S.R. recog­ nized that radiofrequency radiation had unusual effects .upon the human central nervous system. During World War II, Russian radar operators, like ___ their JUnerican counterparts, also complained of headache,

eye pain, ~~d excessive fatigue. However, inst~ad of. dismissing these complaints as irrelevant, Sov~et scientists took them seriously. They conducted full-scale investi­ gations of the health of thousands of people who had been exposed to microwave radiation. Here is what they found: 1. pain in the head and eyes (headaches, eyestrain) 2. dizziness, weariness, general weakness - 24 -

3. disturbed sleep 4. mental depression, moodiness, irritability 5. hyopchondria, f~elings of fear 6. partial loss of memory . 7. diminished intellectual capacity, inabil~ty to:. make decisions 8. diminished sex life in men, lowering of sexual potency 9. stabbing pains in the heart, muscle pain 10. trembling of eyelids, tongue, and fingers 11. dyspepsia, loss of appetite 12. increased perspiration 13. slowed heart rate 14. changes in blood pressure 15. alteration of normal brain wave patterns on examination 16. shifts in white-blood cell counts 17. sterility 18. thyroid problems 19 loss of hair # # # In addition to all of these problems, Russian scien­ tists noticed that microwave workers were fathering an unusually high number of female children. They concluded that this might be a genetic effect caused by exposure to microwave radiation. As it happens, the very same phenomenon had been -­ suggested on a number of occasions in the United Stateso

-- - For example, during World War II, in a radar plant owned by the Spery Rand Corporation, nineteen workers in- a row became the fa the rs of girls. Not surprisingly-; -there -was - - - - considerable mental distress and loss of morale -among ·these' - men. At the time, the medical_ profession dismissed the­ development as insignificant. Later, it was treated as- a joke. However, the effects of microwaves on the human body was no joking matter in the U.S. S. R. and in --other Eastern European nations. In 1958, the Soviet government promulgated an official standard for occupational exposure to microwave radiation. It declared that no worker should be exposed to more·than­ ten microwatts per centimeter squared (10 µW/cm2) during an entire working day. This was 1000 times lower than the guideline that had been recommended in the U.S. The Soviet government alsu laid down strict guid~­ lines for work practices among microwave workers. They included the following: 1. No microwave generators allowed in areas where other work was being performed. 2. Generator antennas must be directed to avoid expos­ ing workers who were operating or servicing them.

j - 26 -

3. Radiation intensities from microwave-generating equipment must be measured every two months.

4. Protective eye goggles must be worn by microwave workers whenever they are exposed to a microwave power density of more than~l mW/cm2. 5. Pregnant women are specifically prohibited from working in areas where microwave levels e-xcee-ded

10 µW/cm2. By way of contrast, such work practices were (and still are) unheard of in microwave plants and installa­ tion throughout the U.S. Indeed, in some American radar factories in the 1950s, female workers wore summer dresses all year round. Was it because of the warmth of the microwave beams to which they were exposed? What accounts for the drastic difference in outlook that has existed for more than twenty years between Russian scientists and their American counterparts over the question of the health effects of microwaves? There are a number of answers to this question: 1. Soviet biologists believe that the central nervous system is the fundamental controlling mechanism of the human body. As a result, they are trained to loci for microwave effects in the modification of the central nervous system, such as behavioral changes. - 27 -

2. American scientists, by contrast, have always be.en skeptical of behavioral data. They are trained to trust only those biological effects that can be observed· ___an_d then duplicated in experimental animal studies .. - - ~• - -3. American biologists and scientists assumed from : -the very beginning that the only possible biological · effect of microwaves was the geating of tissue, and they have been vecy reluctant to change their minds about: ·this. 4. Microwave radiation is used in virtually all of the nation's offensive and defensive weapons systems, .a.nd considered vital to our national security. For this reason, the Department of_Defense, the largest user of RF/MW devices, bas tried to prevent the 10 mW/cm2 guide­ line from being lowered. The fa.ct that during the 1950s · and 1960s the Department of Defense provided most of the money for research into the biological eff e·cits of RF /M:.V · radiation made this task much simpler. However, within the past few years, there has been a drastic change in attitude in the U.S. regarding the potential threat to health posed by radiofrequency and mi·crowave radiation. Here a.re some of the things that have happened: * NIOSH has recently put forth a proposal to lower the guideline for occupational exposure to RF/MW radia­ tion. *OSHA bas become concerned about the scope and mag­ nitude of RF/MQ exposure in the workplace, and is under- - 28 -

taking to measure the radiation levels emitted b~_~adio­ frequency heating, sealing, welding equipment, and other industrial applications of RF/MW. ·· * A proposal has been made by the director of the. New York City Health Department's Bureau for R~diation Control to establish an environmental standard for exposure t9- rrF/MW radiation of 50 microwatts per centimeter squared (50 µW/cm2 ). Community leaders and citizens' groups all over the country have begun to mount legal challenges against the installation of radars, TV broadcast antennas, and micro­ wave communications towers in populated areas. Let us now examine some of the new evidence that had brought this change of attitude about.

The Eff·ects of Low-Level RF /MW Radiation

Between 1950 and 1970, almost no studies of the bio-­ logical effects of low-level radiation were conducted in the U.S. This was because of the erroneous assumption on the part of American scientists that the only harmful effect of RF/MW radiation was the heating of tissue caused by high levels of exposure. Since 1970, however, many low-level exposure studies have been conducted in the U.S., and American scientists = 29 -

have been able to duplicate a number of the Soviet.~nd · Eastern European results. Meanwhile, low-level effects continue to be demon­ strated by scientists in other countries. Low level RF /M.W radiation is generally consj.4ered_ .to_ -- -- __ .- - . · be· any power density below 20 mW/ cm2. For purp9~es of this- - - manual, a thermal (heating) effect is one that entails a net temperature rise in the exposed animal or biological system. Thus, while nonthermal effects may involve sim­ ilar molecular interactions as thermal effects, they_do not entail gross heating of the exposed animal or biological system.

Low-Level Effects Upon the Central Nervous System and the Brain

* Changes in brain wave patterns have been observed in-many studies involving human beings and animals. Some of the brain wave alterations in test animals have c~sn

caused by RF/MW power densities as low as 20 µW/cm2. These brain wave changes often show the same charac­ teristics as sleep rhythnms. This may well explain the many reports of veati.ness, depression, inab_ili ty to con­ centrate, and general sluggishness among microwave workers. * Changes in the behavior of humans and animals have

been observed after exposure, to RF/tflV power levels ranging - 30 -

from 100 µW/cm2 to 15 mW/cm2. ------• Behavioral changes in human beings include the ability of some people to "hear" or perceive pulsed radiation at levels far below the 10 mW/cm2 guideline. This-often occu:rs- as a ticking, hissing, or knocking sensation- within the head~ The phenomenon is not fully understood by scien-­ tists. Behavioral changes in test animals include their in­ ability to perform work tasks when exposed to low levels of ~icrowave radiation, as well as generally decreased physical activity, and attempts to avoid the microwave beam. * Microscopic changes in brain tissues of test an­ imals have been observed after irradiation with power den­ sities ranging from 2-10 mW/cm2. * One o:f the most startling effects of RF/MW radiation is its effect upon the blood-brain-barrier in rats. The blood-brain-barrier is a unique capillary system within the blood vessels of the brain. It prevents-certain sub­ stances from reaching the brain, and it protects the brain from invasion by harmful agents. American researchers have found that the ability of the blood-brain-barrier to keep out such substances is temporarily but markedly reduced when it is exposed to power densities as low as

30 µW/cm2 ! - 31 =

* Another worrisome effect upon the brain is that .. very weak radiofrequency and microwave radiation. at levels below l mW/cm2 have been shown to alter the-chemistry of brain tissue in various test animals. - ·-·•Scientists from Johns Hopkins University,_in Balt=-~ ·1more, found that U.S. Embassy employees in-Moscow-suffered from headache and irritability in much the same manner ., as Russian microwave workers. According to the State · · Department, these employees were exposed to power densities usually' below 5 ~W/cm2! *·The b~a.in operates as an electro-chemical system. Thus it should come as no surprise that electromagnetic energy can alter the bio-electric and chemical function­ ing of the braina French Navy scientists have found serious brain mal­ function in radar workers heavily exposed to microwave. -radiation. In addition, there have been ~eports in the -·U.S. of an increased incidence of cancer of the brain·. in microwave workers. Earlier this summer, a landmark workmens' compensa­ tion case was won by the widow of Samuel Yannon, an em-:- _ ployee of the New York Telephone Company~ who supervised the tuning and servicing of microwave-generating TV antennas on the 87th floor of the Empire State Building. Yannon's physician had diagnosed his condition before death as .;., 32 -

"Chronic brain syndrome with psychotic overtones, due to ·biological brain changes resulting from prolonged exposur.e to heavy doses of short wave radiation." The Workmen's Compensation Board found that Yannon's exposure to microwave radiation caused "brain changes, · tissue destruction, and an acceleration of arterioscler- osis ... " It is obviously of extreme importance that scientists now. determine just how seriously RF/MW radiation can affect the human brain over a long period of time.

Low-Level Effects Upon the Immunologic and Blood Systems )

The body's immunologic and blood systems work to protect us against infectious diseases of many different kinds. For this reason, the fact that dozens of human and animal studies show that RF/MW radiation can produce marked changes in blood chemistry, in the chromosomes of bone marrow cells, and in the lymphoid system is very disturbing. * A recent and very important U.S. study shows an imbalance of potassium and sodium levels in the blood of 2 rats exposed to microwave radiation levels of only 500 µW/cm . Such an imbalance indicates that microwaves may be a cause of high blood pressure. * A combined U.S.-Polish study shows that lymphocyte 2 cells. in the blood of test animals exposed to 15-20 mW/cm - 33 -

.become deformed and then divide in two. This could indi= cate a response of the blood system to a foreign agent=-_

• & in this case 1 microwave irradiation. It could als~ indi= cate the loss of a cellws ability to control its own di= -visiono Another word for that is cancer . . . * Mysterious blood abnormalities, including increased lymphocyte counts, were found in nearly one-third of the State Department employees who worked at the American Embassy in Moscow. These people had been exposed to low­ level microwave radiation over a long period of time . .. No one knows what the significance of their b load abnormali= ties may be. However» a subsequent government study shows that some of these people are developing cancer at an un­ usually high rate. * The fact that microwave radiation can profoundly a.tfect the blood system should come as no surprise. Back in 1962, two researchers at the University of California found that mice exposed over a long period of time to $hart duration, high-level doses of microwave radiation de- veloped leukemia--cancer of the blood--more than three times as much as non-exposed control animals. Incredible as it may seem, this study, which was financed by the U.S. Air Force, was never repeated. The reason given was lack of funds. Thus the minimal level, or threshold dose, for microwave-induced leukemia in mice was never determined. - 34 -

On the basis of this one study alone, however, if microwave radiation were a food additive, it would have to be banned under the law.

- - Officials of the Food and Drug Administration's Bureau of Radiological Health have described this study in an

·-· - official report as highly disturbing. They have· also deplored the fact that no further studies of the leukemia­ producing potential of microwaves have been conducted.

Low-Level Effects Upon the Cardio·vascular System

Electrocardiographic exmaninations of Russian micro­ wave workers have shown numerous changes in cardiovas­ cular function. These include slowing of the heartbeat rate after exposure to microwave radiation at power den­ sities ranging from 100 µW/cm2-10 mlJbm2. In other workers exposed to microwave radiation, Soviet researchers found that the heartbeat rate had been speeded up. Still other Soviet studies show that prolonged ex­ posure to RF/MW radiation can cause hypertension--high blood pressure--as well as hypotension--low blood pressure. A U.S. study shows that when pulsed microwave radiation is synchronized with the heartbeat cycle in frogs, it can not only alter the rhythm of the heartbeat cycle, but can cause the heart to stop beating altogether. - 35 =

Soviet scientists have noted increased vascu~_ar elas­ ticity in microwave workers. An American researcher has theorized that .prolonged exposure to RF /MW radiation may damage the heart and its major blood vessels. -- There have been a number of reports in- the -0' .$. ·alleging a high incidence of coronary heart. disease aJl!Q_ng microwave workers. Why does RF/MW radiation affect the cardiovascular system in such a complex and contradictory manner? One explanation is that microwaves affect the central ~ervous system, which, in turn, sends signals to regulate the hea.rtbeatll and that these signals can vary depending upon which portion of the nervou$ system is irradiated. , Tests on experimental animals indicate that cardio- vascular effects appe_ar to vary according to whi·ch p·art of the body has been exposed to RF/MW radiation. For examplell the heartbeat of rabbits was slowed down when they were irradiated in the belly with 7-12 mW/cm2 micro­ wave radiation. However, when the animals were i--rradiated in the head or vertabral column, the heartbeat was speeded -up. The U.S. Food and Drug Administration's Bureau of Radiological Health (BRH) has pointed out that informa­ tion is lacking about the possible effects of RF/MW radia­ tion on people susceptible to injury because of pre­ existing health conditions. In this connection, it is - 36 -

interesting to note that some Russian researchers have recommended that people with cardiovascular problems be excluded from work involving exposure to RF/W radiatioq.

-Ocular Effects

As previously noted, the eye ~s an organ highly,;v.ul­ nerable to microwave damage because it is poorly equipped with blood vessels, and is thus unable to circulate blood and dissipate heat as effectively as other organs. Scientists in the U.S. and the U.S.S.R. agree that human and animal cataracts can be caused by the intense heating of high-power microwave radiation. There is some disagreement, however, about the effects of low-level RF/W radiation on the eye.

Some U.S. resea~1rersbelieve that 100 mW/cm2 is the level nec~ssary to cause eye damage from single or re­ peated exposures. Other American scientistsestimate this level t·o be about 80 mW/cm.2 . A few warn that cataracts may occur from repeated exposures to RF/MW radiation at far lower power densities.

- One case of cataracts cited in a U.S. government report was described as having developed after a patient was repeatedly treated for sprained neck muscles with a microwave diathermy machine. The estimated level of ex­ posure was 33 mW/cm2 in one eye, and only 2 mW/cm2 in the other! ------37 -

A study of 736 U.S. radar workers and 559 control workers revealed that the men.exposed to radar suffered eye defects and ocular damage at a rate f·ar greater than the people who were not exposed to RF/MW radiation.

More recently, cases of cataracts have been found in the eyes of people exposed to microwave radiation from lea.king microwave ovens. 17 out of 50 employees in a Swedish radar facility \ suffered lesions in the retina of the eye. As a result, the company owning the facility reduced their allowable exposure to microwave radiation from 10 mW/cm2 to 5 mW/cm2 . Retinal lesions have also been observed in the eyes of microwave workers by researchsrs in several other countries, including the U.S. Czechoslovakian scientists state flatly that exposure to microwave radiation accelerates the aging process of the lens of the eye. They stress that eye protection is vital for microwave workers, and that for prolonged occupational exposure, a level no greater than 1 mW/cm2

should be maintained.

As previously noted, Soviet work practice regulations

in effect since 1958 have required that Russian workers wear protective goggles when exposed to microwave power dansities of more than 1 mW/cm2. A recent report published in the British Journal of Ophthalmology by two American researchers describes nine cases of cataracts thought to be by RF/MW radiation - 38 -

among people working in the aviation industry. The-nine __ patients included three radar technicians, five- air-traffic _controllers, and one airline pilot. All of these people were exposed to PJ'/Mw radiation power densities below l mW/cm2. In the U.S., a number of former Air Force radar technicians have been awarded compensation by the Veterans Administration for cataracts caused by exposure to micro­ waves. In addition, several air-traffic controllers have· received compensation awards for microwave-induced cata­ of Labor. racts from the Department . It seems obvious from all of this that RF/'MJI radia- tion is particularly hazardous to the eyes. It is also apparent that the present recommended guidiline for occu­ pational exposure to radiofrequency and microwave radia­ tion (10 mW/cm2 ) may not be adequate to protect workers from eye damage.

Effects~ the Reproductive Organs

Earlier in this manual, it was noted that, 'like the eyes, the testicles are especially vulnerable to micro­ wave damage. Note was also taken of the fact that during the early p~rt of World War II, rumors spread through the U.S. Navy that radar could cause sterility. You will - 39 -

remember that upon investigation the Navy could not find any substantiation for such stories. However, in 1968, two U.So Air Force doctors pub­ lished an article in the Journal of American Medicine describing in great detail the case of a radar repairman who had become sterile as a result of exposure to intense microwave radiation. Since then, dozens of cases of sterility caused by

RF /MW radiati.on have been reported. And the Veterans Administration has awarded compensation for·some of these cases. Soviet researchers have reported damage to the gonads and sperm of male microwave workers since the early 1950s. They have also observed altered menstru~l activity in female microwave workers. A recent report from Rumania, which was published here in the U.S. in Health Physics, reveals that 22 out of 31 microwave technicians experienced temporary loss of sexual en~rgy and reduced sperm production. These men were exposed to microwave radiation power densities that ranged merely from tens to hundreds of microwatts per centimeter squared! - 40 -

Genetic E'ffects

You may remember that in the introductory section of this manual, it was noted that in 1971 the Electromag-

- .. netic Radiation Management Advisory Council of the Pres- ident's Off ice of Telecommunicat.ions Policy warned that- . long-term, low-level exposure to RF/MW radiation "could become a critical problem for the public health especially if genetic effects ·are involved." The genetic effects of exposure to RF/MW radiation - have been investigated over a wide range of frequencies and power densities in both animal and plant systems. Mutations and adverse effects on growth have been in­ duced in test animals exposed to 5 mW/cm2 or greater. Polish scientists have conducted many studies showing that both high and low-level 'RF/MW radiation can change and damage the chromosomes of test animals. This damage can occur at thermal and nonthermal power densities. Chromosomes, which are found in human and animal cells, carry the genes and transmit hereditary characteristics. Scientists at the U.S. Environmental Protection

Agency (EPA) have found that when pregnant mice are , sub- jected to microwave radiation having a frequency of 2.45 GHz (the frequency of most microwave ovens) and power densities ranging from 3.4~28 mW/cm2, they delivered - 41 -

litters in which there was a significant increase of a

birth defect known as exencephaly--a so-called hernia of the brain in which the brain develops outside of the skull. In the early 1960s, scientists at Johns Hopkins University, in Baltimore, conducted a study to determine the ca.use of Down':s Syndrome (Mongolism) in 216 children suffering from this serious birth defect in Greater Balti­ more. They found that almost 10% of the fathers of the . children afflicted with Downr s Syndrome reported "intimate contact with radar both in and outside of the armed services." A subsequent study did not corroborate this apparent

link between radar and Down rs Syndrome~ However, it did show that men exposed to radar have a significantly higher number of chromosomal abnormalities in their blood than men who were not exposed. It is well known in medical circles that chromosomal abnormalities can cause birth defects. In the late 1960s, the U.S. State Department conducted secret tests on some of its young female employees at the American Embassy in Moscow to see if they were suffering form any genetic damage due to the microwaves that were being beamed into the Embassy by the Russians. A signifi­ cant number of these women were found to have chromosomal abnormalities. One doctor involved in the study recommended - 42 -

that the women be withdrawn from the Embassy to avoid further genetic damage from microwave radiation. None­ of·the women was ever informed of the reason_for the ·tests or their results.

An association between microwave radiation a.rid in~­ creased. birth defects of various kinds has been r.eporte_d among Army helicopter pilots exposed to radar, as well as among commercial airline pilots. Neither of these groups has been thoroughly investigated. A higher-than-normal infant mortality rate has been reported at several military bases known to have heavy concentrations of radar. No investigations of these reports have been undertaken by the Department of Defense. Scientists in California recently irradiated 33 pregnant squirrel monkeys with microwave power densities of 10 mW/cm2 during the second and third trimester of pregnancy. The offspring of these monkeys were then irradiated for up to six months after birth. Four out of five of the irradiated baby monkeys died,- as compared with no deaths in a group of non-irradiated control animals. The question of whether exposure to RF/M:W radiation could have serious genetic consequences is wide open and needs to be thoroughly investigated. In one study, a single heavy radiofrequency exposure for 10 minutes at 27.12 MHz (a frequency employed by·many - 43 =

RF heaters and sealers) between the first and sixteenth day of pregnancy caused birth defects in the offspring of rats. Because of reported changes in menstrual patterns, increased miscarriages, and birth defects, women of child­ bearing age are prohibited from working with RF radiation equipment in Czechoslovakia. Meanwhile, in the U.S.A., 75% of the workers using

RF sealers are being exposed to peak radiation levels higher ·than 10 mW/cm2 . Average exposures exceed 10 mW/cm2 for approximately 10% of these workers. A majority of those exposed to this excessive level of RF radiation are women of child-bearing age.

The Cancer Connection

It has sometimes been said that there is no clinical evidence that B:F/MW radiation is carcinogenic--meaning that it ca~ cause cancer.

We have already referred in this manual t.o a study performed at the University of California, in 1962, which showed that long-term exposure to short-duration, high= level doses of microwave radiation caused leukemia--cancer of the white-blood cells--in mice. What remains to be seen is whether long-term exposure to low-level RF/MW radiation can cause cancer. Incredibly, almost no animal studies have been undertaken to determine the.answer to this important question. It is fair to say that at the present time the evi­ dence linking rrPJ'MW radiation to cancer is speculative and ... circumstantial. However, there are many disturbing reports that RF /MW radiation has caused cancer in humans.· Here · · · are some of them: * At the Naval Air Station at Quonset Point, R.I., 3 out of 8 employees engaged in the overhaul and repair of radar equipment have either developed cancer or died of it since 1970. Two of the men (aged 31 and 35) who sat side by side at the same test bench developed cancer of the pancreas. This is extremely rare, because 99% of all reported.cased of pancreatic cancer occur in people over 400 As a result of the Quonset Point sit~ation, NIOSH is planning to undertake a large-scale study of the causes of death among workers exposed to RF/MW radiation. * Accoraing to a recent World Health Organization (WHO) study, people living in Finland near the Soviet bor­ der, where the Russians have installed their early warning radar, have experienced an unusual increase in the inci­ dence of fatal heart attacks, as well as an unexpected a.nd· unexplained increase in the incidence of cancer. The WHO survey indicated that there was a correlation between these health problems and the installation of the Russian radar on the other side of the border. - 45 =

* The Johns Hopkins University study of the health experience of people living and working at the American Embassy in Moscow shows that an unusually high rate of cancer has occurred among the female employees. No ex­ planation has been forthcoming. These women, however, were exposed to low-level microwave radiation beamed into the Embassy building by the Soviets. * During the late 1960s, two cases of rare brain tumor occurred among 23 men working on classified micro­ wave listening equipment at a Philco-Ford factory in Phil= acelphia. This was almost 2,500 times the expected rate. * An unusually high incidence of cancer of the uterus­ has occurred among women living in a section of Portland, Oregon, where there are many large TV and FM radio antennas. According to the EPA, this area has the highest level of broadcast radiation ever measured in the ambient air of any American city. *Asimilar cluster of cancer has been reported among people living in the vicinity of a hilltop antenna complex south of Syracuse, New York. The report was published in the New York State .Journal of Medicine . . * Another cancer cluster has been reported in Ruther­ ford, N.J., where the rate of leukemia among children attending the Pierripont Elementary School is six times the national average. As it turns out, there is a huge complex of radio and TV transmitter towers close by the - 46 -

Pierrepont School. In addition, ITT has conducted radar testing in the vicinity for many years. While such reports do not "prove" that RF/MW radiation is carcinogenic since such clustering of cancer cases· could occur by chance, they certainly provide us s·ome-thin:g to • worry about. · According to a recent NIOSH report, the possibility that occupational exposure to B:F/MW radiation may be car­ cinogenic "should be closely examined."

What Remains to Be Done

At this point, it seems obvious that much scienti­ fic work remains to be done concerning the long-term, low-level biological effects of radiofrequency and micro­ wave radiation. Key areas of concern are: * the central nervous system * the blood-forming system * the immunologic system * the cardiovascular system * the eyes * the reproductive organs * the genetic system There is also a great need for sound epidemiological studies to determine the effects of RF/MW radiation in I = 47 -

human beings. Epidemiology is the study of disease in defined populations. The fundamental epidemiological questions regarding RF/MW radiation are these: What kinds of disease, and how many cases of desease, are developing in specif±c groups of people who are occu­ pationally and/or environmentally exposed to radiofrequency and microwave radiation? Up to this point, epidemiological studies of RFfM.W effects have been few in number and limited in scope. Some of them have been poorly conducted. For example, the much-publicized study of the health of the State Department employees at the American Emabssy in Moscow was seriously flawed in the following ways: a. The length and intensity of the microwave expo­ sure was never independently investigated or established. b. The health experience of people who lived and worked in the Embassy building, where the radiation ex­ posure occurred, was lumped in with that of hundreds of other poople who lived elsewhere and obviously had little or no exposure to microwave radiationo c. The response rate to the health questionnaires was extremely poor. As a result, the study provides a grossly incomplete record of the health experience of the Moscow Embassy employees. d. The validity of the control group (people living in other Eastern European Embassies, who were not supposed • - 48 -

to have been exposed to microwave radiation) was totally

.. . ~ ·- compromised by information indicating that-these control sUbjucts had, indeed, experienced microwave exposure. Another epidemiological study which examine·d ·causes of death among 20,000 Navy personnel· exposed ta~- microwav·es,

and compared them with 20,000 Navy control pe·rs·onnel not exposed, was almost laughable in its inadequacy. The - Navy was allowed to pick the control groups for the study. One of these control groups consisted of radarmen! Obvioµsly, the time has come for thorough-a-ad i-n-de-pendent------­ epidemiological studies of workers who have been occupation- ally exposed to RF/MW radiation over a long period of time. Incredibly, no such studies have ever been undertaken in the U.S., except for some surveys of the e~fects of micro- wave radiation upon the eyes of radar technicians. Groups that should be studied include mi!'itary radar operators, radar repairmen and troubleshooters, microwave oven repairmen, helicopter pilots, radio and TV broad­ cast antenna maintenance crews, diathermy machine· opera­ tors, and workers who use RF heaters and sealers. Some ~ajar elements to be determined in these epi­ demiological studies are behavioral changes, catar.acts, abnormal or low sperm counts, genetic defects, birth defects, and cancer. - 49 =

Cumulative E'ffects

It is well known that the.damage inflicted on living tissue by ionizing radiation such as X-rays is cumulative. This means that the harmful effect of each successive exposure builds up over a lifetime. It explains why med­ ical authorities are warning people to avoid all unneces ·sary exposure to ionizing radiation. People in the electronics industry and the military establishment claim that non-ionizing radiation such as radio waves and microwaves do not have cumulative effects. However, there is considerable disagreement on this issue. A recent FDA report on the hazards of microwave ovens puts the problem this way:

"The possibility that cumulative ef.f ects of micro­ wave radiation can occur has been raised through research, and cannot be ignored. The potential exists for exposure of young and very young people repetitively as ovens come into common usage 1 and effects may result. Substant~al follow-up of exposed populations will be needed to examine the question of such effects." How about substantial follow-up of the 10 million or so workers who are being repeatedly exposed to high radiation levels from RF heaters and sealers? - 50 -

Combined Ef'fects

Combined effects are particularly worrisome when one is considering exposure to any toxic agent. For example, asbestos and cigarettes form a deadly combination. Indeed, asbestos workers who smoke a pack of cigarettes a day have 90 times the chance of developing lung cancer as people who neither work with asbestos nor smoke. In this connection, RF/MW radiation is known to act in combination with a number of-other agents. It has been known for some time that microwaves can interact with X-rays, although the mechanism of such inter­ action is not well understood. It has been shown, however, that pretreatment of tissue with microwave radiation en­ hances the effect of high-level X-ray exposure. Some studies have shown that microwaves act in combi­ nation with certain tranquilizers and other neuroactive drugs. For example, tests in rats indicate that micro­ waves intensify the effect of a tranquilizer called chlordiazepoxide. An obvious interaction is that of RF/MW radiation with heat and humidity. A number of Eastern European studies show that exposure to 'RF/MW in high temperatures produces significant changes in behavior and cardiovascular function. Other investigations suggest that any organism previously exposed to a stress agent such as heat may be - 51 =

- -· -particularly vulnerable to the action of another stress agent-such: as microwave radiation. It has be.en suggested by Ea.stern European sc-ientists __ that RF /MW radiation may interact with trace me.ta.ls- that. - have been~ deposited within the body. In any c~~e_,: _it has-: - - been shown that microwave radiation can interact: :with- met~-1- -.. surgical implants and cardiac pacemakers. Indeed, the man- ufacturers of copper loop IUD devices warn woman wearing such devices never to undergo RF/MW diathermy treatment!

Pulsed vs Continuous Wave (CW) Exposure

The present recommended guideline for occupational exposure to RF/MW radiation is based upon the belief that the only harmful effect of such radiation is the·average heat load it deposits in the human body. For this reason, 2 official field surveys to determine whether the 10 _mW/cm guideline is being observed allow RF /MW power density- ~~vels to be ~ime-averaged. Yet people working with radiofrequency heat sealers are routinely exposed to peak radiation levels that may exceed the 10 mW/cm2 standard by more than 100 times! Time-averaging means that in the case of such devices as radar, which uses pulsed microwave energy, the peak power of each microwave pulse is not measured. Rather, this peak pulse, which may be hundreds of mW/cm2, is - 52 -

time-averaged with the time segments between the pulses when there is no exposure. Only the average power over a period of time is included in the calculations. As long as tb.e average is less than 10 mW/cm2, the exposures are considered within acceptable limits. The trouble with this practice is that it ignores steadily mounting evidence, both here in the U.S. and overseas, that the instantaneous, nonthermal effects of being bombarded several hundred times a second by powerful peak pulses of radiation may prove to have serious biologi­ cal consequences in the long run. The following are some of the. suspected effects of low-level, peak pulse radiation, 0 for which there is evidence from animal tests:

1. Changes in the bib-electric function of the bra.in at levels as low as 30 µW/cm2. 2. Changes in brain chemistry at 100 ,uW/cm2.

3. Changes in the permeability of the blood-brain- barrier--the membrane that prevents harmful substances from reaching the brain--at levels ranging from 10-200 uW/cm2 . 4. Changes in the immunologic system, which protects the body against infectious disease, at 300 uW/cm2. In the face of all this evidence that RF/MW radiation may be far more dangerous to human health than anyone expected, spokesmen for the electronics industry and the military establishment are fond of reminding people that = 53 =

biological effects or changes 9,0 not always constitute hazards to human health.

This is often true. _ B_ut ~houldn' t a sensible society assume that changes ·

. - in t_b.e bio_electric function and chemistry of tlfer brain, · · a.__nd in the immunologic system, are hazardous unti1 it ·can be proven otherwise?

Victims of B.F/MW Radiation

The sad price of neglecting the problem of occupation­ al exposure to any toxic agent is always that unfortunate and unsuspecting workers become the victims of disease, disability, and death. Neglect of the problem of occupa­ tional exposure to RF/MW radiation on the part of govern­ ment and industry has led to the same result. Within recent years, compensation has been awarded ·

- . -· for cataracts, sterility, and brain damage caused by R:F/MW radiation. "Radiowa.ve sickness," as it is called by the • I

R~ss i ans , _ has been a comp ens ab le disease in the U. S . S ·e R. for at least twenty years. No one really knows~ of course, how many if any workers exposed to PJ'/M,W radiation in the U.S. have developed cataracts, how many have become sterile, or how many have suffered cancer or b~ain damage, as claimed in the case of Samuel Ya.nnon, the former employee of New York Telephone. No one knows because no one has really - 54 -

begun to look for RF/MW disease among workers. This is why epidemiological studies of exposed worker populations are desperately needed. Meanwhile, two organizations have been formed to help the victims of RF/MW exposure. For the past ten years, one vehicle of information and support for the 150-odd ex-servicemen and air-traffic controllers who have developed cataracts from microwave exposure has been an organization called Radar Victims Net­ work. This outfit was founded by Joseph H. Towne, a former radar technician who developed cataracts after serving on EC-121 radar spy planes. Radar Victims Network is located c/o Joseph H. Towne, 6736 Medora Drive, North Highlands, California 95660. Another organization acting in behalf of workers suffering from rrF/M.W injuries is the Microwave Radiation Foundation, c/o Arthur Massara, 26 Grove Street, Arlington, Massachusetts 02174.

Public Concern and Litigation

When the representatives of government, industry, and the scientific and medical community fail to deal with the problem of occupational and environmental disease, workers and other people who are afflicted have recourse to public action and litigation. = 55 -

Within recent years, the number of workmens' compen­ sation cases and other lawsuits regarding RF/fflV disease has increased tremendouslyo There are dozens of cases before .. the Department of Labor concerning microwave-induced catar= acts. In fact, the DOL has creat-ed a special claims branch to deal with such cases. Other lawsuits across the nation involve injuries .. allegedly sustained from exposure to microwave ovens, FM and TV broadcast antennas, FAA and military radar, and

Citizen Band (CB) radios. Moreover, in cities and towns all over the U.S., citizens groups are opposing the installation of FM and TV broadcast transmitters, radars, and other RF/MW genera= ting equipment. Such efforts have been mounted in Cal­ ifornia, Oregon, Nevada, Illinois, Massachusetts, Missouri, Montana, Maine,Connecticut, New York, New Jersey, Penn­ sylvania, and Ohio. In light of recent experience with other toxic agents, it 1~ not hard to predict that the number of lawsuits and the amount of public opposition will increase tremendously within the coming years.

--- - ,vii-ere· To Find Additional Information About RF /MW:

* The New Yorker, December 13 and 20, 1976, "Micro­ waves," Part I and Part I I, Paul Brodeur - 56 -

* ~ Zapping of America, W.W. Norton, N. Y. ,Paul PauL:. Brodeur * Saturday Review, Sept 15, 1979, "The Invisible Threat," Susan Schiefelbein * New York Magazine, June~ 1980, "Living with Micro­ waves," Jill Jonnes * Science, Vol.208, June 13, 1980, "The Origins of U.S. Safety Standards for Microwave Radiation" ------57 =

PART V

PREVENTING HARMFUL RF/MW EXPOSURE

_ The Present Standard and How 12 Use It

The present standard for occupational exposure to 2 RF/MW radiation of 10 mW/cm is obviously inadequate. For example, the guideline provides little protection against long-term, low=level effects. Consider for a moment the occupational exposure standards in Sweden and Canada: 1000 uW/cm2 (10 times lower). One: might ask what do these countries know that we in the U.S. do not? The correct answer would be nothing. A~ this manual clearly indicates, scientists in the U.S. do -accept the many nonthe:rmal, low-level effects of RF/MJI radiation. But our regulatory agencies have bent to the anti-regulatory mood of the Congress and done nothing! 2 However, some important modifications in the 10mW/cw standard have been made within the past year. And some new changes will be made in the near future. On September 26, 1979, OSHA issued an Administrative Notice on nonicmizing radiation. The notice was designed to establish a uniform citation control procedure for RF/MW radiation in general industry. The most meaningful change in the OSHA notice is that it establishes a new way of = 58 -

measuring electromagnetic radiation intensities in the near field--in other words, close·to the source of RF/MW power. Where most significant occupational exposures occuro This is particularly important for the operators of RF sealers and heaters, which use frequencies ranging from 5 MHz to 100 MHz. The operat.ors of such machines stand in the near-field (since it may extend 30 meters from the RF power source). Unpredictable radiation patterns exist in this area which cannot be properly measured in terms of milliwatts or microwatts per centimeter.squared. For this reason, the OSHA Administrative Notice pro­ vides that near-field RF intensities be measured in terms of electric field strength and magnetic field strength. Electric field strength (E) is measured in terms of volts per meter. Magnetic field strength (H) is measured in terms of Amperes per metero An electric field strength of 200 Volts/Meter and a magnetic field strength of .5 Amp/Meter is considered to be equivalent to the power density level of 10mW/cm2 in the far field. The OSHA Administrative Notice provides that if, during the course of an inspection, employees are found to be expo~ed to ele~tromagnetic radiation in the frequency range from 10MHz to 100GHz, serious citations shall be issued if: - 59 - r I .

a. The energy density levels averaged over 2 6-minute period exceed lOmW/cm . b. If one or more employees are exposed to electromagnetic levels at or above an electric field

strength of 200 Volts/Meter, or a magnetic field strength of .5 Amp/Meter averaged over any 6-minute period.

Recent Efforts to Lower the Standard

Within the past two years, the National Institute for Occupational Safety and Health (NIOSH) has prepared a draft criteria document on RF/MW radiation and issued a proposal 2 to lower the 10 mW/cm standard. The NIOSH document pro= poses the following changes: * 1 mW/cm2 for frequencies between 10 and 400 MHz. (This would primarily affect operators of RF heaters and sealers, as well as personnel working near radio and TV broadcast antennas). 2 * 5 mW/cm for the frequencies between 2 and 300 GHz. (This would affect radar technicians, military personnel, and communications workers.) * The NIOSH proposal also addresses frequencies below 10 mHz. * For the middle frequencies (400 MHz to 2 GHz) NIOSH proposes that the allowable power density

•...__,,,· increase as the frequency rises. - 60 -

These NIOSH proposals have come under heavy attack from members of the scientific community and from organized labor. The chief criticism of the NIOSH draft criteria document is that it assumes that the way RF/MW radiation affects the body is directly related to the amount of energy the body is absorbing. For this reason~ officials of the AFL-CIO, together with several leading RF/MW scientists, have asked NIOSH to issue an interim criteria document recommending that OSHA adopt an interim standard of 1 mW/cm2 for all fre­ quencies from 10 MHz to 300 GHz. This would afford more protection to the millions of workers who are now being exposed to RF/MW radiation. These officials have also called upon NIOSH to develop a more comprehensive criteria document that would better reflect the long-term, low-level effects of RF/MW radiationo

What You Can Do to Protect Yourself

The whole history of occupational health standards can be rather easily described. To begin with, the standards are always set too high. Then, as workers begin to sicken and die, the standards are lowered. And lowered again. And again. This has been the case with asbestos, beryllium, benzidine, X-rays, radon daughters, and vinyl chloride--to name just a few of the more dangerous toxic agents. It is now the case with RF/MW radiation. - 61 -

The essential question thus becomes what to do in ------the meantime? How can a worker protect himself against health damage from RF/MW radiation until a meaningful - -­ standard is promulgated and enforced? one obvious answer is to avoid exposure-whenever- - :· possible. Sometimes this is difficult because RF/MW radiation cannot be s,een, and can only be felt as heat·· when the levels are dangerously high. Here are some things to keep in mind: l. Know what kinds of devices emit RF/MW radiation. 2. Confirm through other sources.that_what employers or manufacturers tell you about such equipment is true. (For example, employers have been telling workers that RF heaters are as "safe as a CB radio." This is untrue on two counts. The fact is, RF heaters have been demonstrated to be very unsafe by the government. And government tests show that, when transmitting, CB radios can emit relatively high levels o! RF radiation). 3. Assume that all RF/MW devices may be emitting ha.rm:ful levels of radiation until measurements prove otherwise.

Other Hazards

In addition to the health risks already discussed, RF/MW-generating equipment can present other serious hazards to the unwary worker. Here are some of them: - 62 -

* X-Rays--During normal operations, radar power tubes produce X-rays. When such tubes operate in excess of 10,000 volts, stray X-rays may be emitted. Special precautions and shielding measures must be taken when voltages approach or exceed 15i000 volts. Monitoring equipment should be used to periodically check the level of X-radiation emitted by high-voltage power tubes. * Radioactivity--Certain radar component tubes may also contain small quantities of radioactive material. If such tubes should be damaged or fractured, workers must

be careful not to ingest or inhale the material. Tubes containing radioactive material should ""'· __.,, not be stored in large quanitities unless their level of radioactivity is periodically checked and found to be acceptable. Work rules governing the handling, use, and storage of such tubes should be posted and strictly enforced. * Electrical Hazards--All terminals on high­ voltage electrical equipment operating in excess of 50 volts should be enclosed or otherwise protected. Such equipment must be grounded in such a way that no high electrical potentials can exist between the unit. * Fire Hazards--Radar equipment can cause the ignition of flammable materials (fuel, explosives) by the inductive heating of steel, other metals, or metal wools, - O.:> -

or by sparks produced across a small gap between metal

.. elements in _an area in which an explosive fuel-air mixture may be present. RF/MW equipment, such as radar and two~way radios, should not be operated near electronically detonated explosives. The energy of the radar or radio may be ·suf= ficient to ignite fuses at a considerable distance.

Typical RF/MW Devices in the Workplace

Let's take a quick look at some typical RF/M!N device~ in common use in the workplace, and some typical exposure levels experienced by people working with them. Exposure Levels rce Frequency Use Occupational Exposure Possible Maximum

2 welders 3-6MHz metallurgy, factory workers» foundry more than lOOOmW/cm furniture workers, welders 10mW/cm2 veneering 2 gluers, 10-lOOMHz 25,000 in use factor workers all across 88 500mW/cm ers, heat­ in U.S. (See the nation ' sealers NIOSH-OSHA table) 2 ctro­ 30MHz All operating operating room personnel 19 70mW/cm gical rooms to cut and patients ts and sterilize flesh 200mW/cm 2 izen Band 27-164MHz 30 million in policemen, firemen 0 mobile " ) radios, use in U.S. unit personnel, anyone very ile unit today close to a CB transmitting ios antenna 2 2 rowave 2450Amz 10 million in restaurant workers, hospital lOOuW/cm 100mW/cm ns use employees, housewives, to 5mW/cm 2 children 2 adcast lOMHz- nationwide broadcast transmitter tech­ luW/cm~ to 50-lOOmW/cm ilities 3000MHz nicians, repairment, TV lmW/cm TV workers 2 2 ars 30MHz-300 nationwide, radar operators, radar re~ 10uW/cm to 200mW/cm GHz military bases, pairmen, shipboard personnel, 50mW/~m2 airports airport workers, pilots, air crews, Air Traffic Controllers fishermen - 65 -

I OSHA and NIOSH should undertake without any further delay to impleme.nt a new standard for occupational exposure to RF/MW radiation. The new standard should require periodic monitoring of­ emission from RF/MW devices, radiation shielding, protective equipment, goggles to protect the eyes of workers, when appropriate, and adequate hazard training and work prac= tices. (For example, all workers using RF/MW equipment should be informed of the hazard of wearing metal jewelry, - or touching metal work tables. This can create an antenna effect and increase one's absorption of RF/MW energy). Local unions should check to see if RF/MW equipment is being used in their factories or offices. The frequency and RF/MW emissions of any such equipment should then be measured and monitored. Adequacy of radiation shielding for RF sealers and heaters should be ascertained. Haza.rd training of RF machine operators and maintenance crews should be_undertaken. -- Finally, do not hesti tate to request an OSHA :!.nspection if you feel that high levels of RF/MW may be coming from equipment in your place of work. OSHA has the power to issue a violation to cite an employer for a "recognized hazard. 19 The OSHA Administrative Notice of 1979 brings RF/MW radiation under this category. - 66 -

------FM Radio and TV Towers Earlier in this manual, we discussed the case of the late Samuel Yannon, an employee of the New York Telephon~-­ Company. Yannon sustained heavy exposure to-RF/M.W_radia~_­ tion while working with· TV transmitters on the 87th floor­ of the Empire State Building. As a result, he allegedly suffered serious brain damage, tissue destruction, and an acceleration of arteriosclerosis. FM/TV towers can either be stru~turai steel towers, or they can be located in tall buildings such as the Empire State Building or the World Trade Center in New

York City. ... ./ Robert A. Curtis, of the OSHA Health Response Team, 390 Wakara Way, Salt Lake City, Utah, 84108, (Telphone: 801/524-5896), recently made a survey of occupational exposures to RF/MW radiation from FM radio and TV _antennas at seven transmitting facilities in the U.S .. -.Here is what he found: * RF/MW radiation levels in transmission 2 monitoring rooms were generally well below the lOmW/cm OSHA standard. However, leaks in transmitter cabinets, conduits, and transmission cables resulted in localized "hot spots" with RF levels that exceeded the OSHA standard. * RF/MW levels at various locations on the antenna towers greatly exceeded the 10mW/cm2 standard. - 67 -

Antenna towers are routinely climb'ed by employees at Fij/TV facilities in order to perform maintenance such as painting, antenna adjustment, replacing aircraft warning beacons, repairing de=icing equipment, and ma1ntaining the - structural components of the tower. Very often, -these people work on the towers when the radiating -erements are in operation. Many FM/TV towers have multiple antennas. As an employee climbs up the tower to work on any of the higher antennas, he must pass through the radiating pattern of th~ lower antennas. Here is an example of what can happen. On the 77th floor of a skyscraper housing a single FM radio station, a worker temporarily lost consciousness and was founding lying within 4 feet of one of the steel access doors ·to an FM antenna. The access dooor had been left open. An OSHA survey was initiated as a result. Near the opened door the electric and magnetic fields measured approxi­ mately 2.5 mW/cm2 . However, when the measuring probes • -were held two feet through the access doorway, at a point 3 feet below one of the FM radiating antennas, the intensity 2 of the RF radiation increased to more than 100 mW/cm ! The OSHA survey team found similar levels on other towers housing FM/TV transmitting equipment. An EPA survey 2 measured a level of 180 mW/cm near the radiating elements of an FM radio station. - 68 -

, , Personnel working on activated FM radio and TV antenna towers are routinely being exposed to excessive . FfF/MW fields with no knowledge of the health hazards involved. Very few FM/TV towers of the hundreds that are now in operation in the U.S. have been surveyed for RF/MW hazards. Robert Curtis, of OSHA, recommends that a written RF control program be established for each FM radio and TV broadcast facility in order to insure the protection of workers against RF/MW hazards. His comprehensive program includes employee training and the identification of restricted areas--locations where RF/MW field exceed the OSHA standard. In the absence of a comprehensive RF survey, Curtis recommends that the following be designated as restricted areas: 1. Any location within the principal radiation pattern of a major antenna. (A major antenna is one with an output greater than 50 watts). 2. Locations closer than 25 feet from a radiating element of a major antenna. 3. Locations within 2 feet of all activated antennas and transmission cables and conduits. All restricted areas should be clearly marked with standard RF hazard warning signs. - 69 -

The entrance of a worker into a restricted area

requires the deactivation of RF sources to reduce hazard= ous exposures. Transfer of transmissions to a strategically located standby antenna will allow for continuous broadcasting. Administrative and/or physical "lockout" procedures should be utilized to insure that RF sources remain inacti= vated for the entire times workers are occupying a restricted area. Persons responsible for administering and implement= ing the various elements of the RF control program should be clearly designated. This is particularly important because each antenna-tower station is owned and/or operated

by multiple sources. Curtis ·suggests that prospective FM radio and TV . boradcasters submit a copy of their control program as part of their application for FCC licensing. Working on FM/TV towers can be extremely hazardous. Hundreds, perhaps thousands, of employees on such towers have sustained heavy exposures to RF/M.W radiation. A study of their long=term health experience should now be under taken by NIOSH. Meanwhile, further exposures should be drastically reduced. The impetus for this must come from the employees and the employers involved. ------70 -

The Special: Problem of RF Sealers and Dielectr-rr ffeaters-

NIOSH/OSHA Current Intelligence Bulletin S-3"-su-ouldoe---

- ·------distributed to and read by all workers who are exposed to RF/MW radiation. Bulletin 33 deals with RF he-a:-'terS ___and sealers. Here are some important points it makes: * "Workers near RF sealers may be unaware of their exposure to RF emissions because the RF energy from sealers and heaters can penetrate deeply into the body without activating the heat sensors located in the skin. A false sense of employee security may exist ... " ·-, * "Recently, monitoring instruments that facili­ I __)' tate accurate measurement of worker exposure have been developed. Federal survey teams, equipped with t~ese new instruments, have detected excessive exposure of workers to RF energy." * "Absorptions of RF energy also result in 'non- - thermal' effects on cells or tissue, which may occur with­ out measurable increase in tissue or body temperature." * "Humans can absorb RF energy at frequencies used by most RF sealers and heaters ... workers near RF sealers and heaters can absorb considerable amounts of the stray energy emitted from the RF machines." * "Contact of the workers with an electrical ground plane ... could increase the amount of en£rgy absorbed by the workers and worsen the exposure condition. RF - 71 -

shtelding material incorporated into the floor, walls, and ceiling of some RF workrooms could constitute such a ground plane ... " Dielectric heating was introduced unto the workplace in about 1940, and was first used for heating plywood. Dielectric heaters are usually employed for treating non= conducting materials such as wood, plastic, and leather. The load to be heated is placed between two plates of the capacitors, called electrodes, which are connected to a source of high frequency power. When irradiated in the high frequency field, the molecules of the material become agitated. This causes the material to heat through molecular friction. Dielectric heating equipment usually operates in the Industrial Scientific Medical (ISM) band assigned by the Federal Communications Commission (FCC). The ISM band frequencies most commonly used are 13.56 MHz, 27.12 MHz, and 40.68 MHz, where the power output of the RF source is unlimited. In a recent survey in the U.S., it was found that more than 50% of the plastic sealers operate between 25 and 30 MHz. The most common dielectric heater is the plastic welding machine (i.e., RF heat sealer). In this type of operation, the electrodes are usually not shielded since this would prevent the operator from viewing the welding process. As a result, the operators of most plastic welders - 72 -

and sea_lers are being exposed to high levels of RF radiation. In a recent NIOSH survey, it was found that·the _electric field of p-Ja.stic welders exceeded the OSHA_ . standard 60% of the time, and that the magnetic_ ~ield - was too high in 29% of the tested equipment.- These measurements were taken at distances less than one meter from the RF source, where operating personnel are usually stationed. Swedish investigators have found that the power lines leading to plastic welders can often become effective antennas for RF radiation. So can metal racks and stands ) which may be located in the vi·cini ty of RF sealers. Power- f~l electromagnetic fields can thus be re-radiated some distance from the RF source. During OSHA inspections of plastic welders in the U.S., it was found that proper shielding can substantially reduce operator exposure. Such schielding is available from many RF sealer manufacturers. If the RF sealers you are working on do not have shielding, make an issue of it with management. The NIOSH survey also disclosed that RF leakage from adjacent sealers can be comparable to that emitted by the RF sealer being tested. - 73 -

The NIOSH and OSHA surveys found that almost all the . . RF sealers measured were being operated by women. NIOSH investigators warned that biological effects uniquely associated with women, such as fetal deformation and miscarriage, must be considered. This, of course, is why women of child-bearing age are prohibited from working with RF equipment in Czechoslovakia. The NIOSH people noted that magnetic field strength exposure cannot be measured in the near-field (i.e., close to the RF source) with far-field power density monitors. It is important to remember in this connection that dif­ ferent equipment must be used to measure the electric and the magnetic fields. Make.sure that when RF sealers in your workplace are being surveyed, the proper equipment is being used. Such measuring equipment has been developed for NIOSH by the National Bureau of Standards (NBS). The NARDA Corporation Model 8633 and 8635 magnetic field strength probes with the Model 8644 electric field strength probe is also recommended. In addition to acute and chronic health effects from exposure to radiation leakage, RF heaters and sealers pose other hazards such as electrical shock and burns to operating personnel. Improper installation of RF equipment can include: 1. poor location 2. lack of proper grounding - 74 -

3. inadequate interlocks and controls 4. inadequate shielding Unsafe operating practices include: 1. unauthorized and untrained personnel-working with RF equipment 2. unauthorized adjustment of controls 3. reaching into conveyors to adjust or extract material 4. failure to shut down equipment and report operating defects

I Faulty maintenance practices include: 1. poor maintenance schedules 2. unauthorized repairmen 3. failure to shut off power and use _lockout procedures before servicing 4. not discharging capacitors (the stored-up charge can have lethal potential) 5. failure to short high-voltage leads to ground before working on equipment. Newer RF equipment usually has activation swtiches that keep hands from being crushed by the jaws of the RF machine, or shocked during activation. However, older machines can cause serious arc burn. This occurs when electrical current from the machine arcs to the bone in the finger, resulting in the destruction of the tissue between. - 75 -

Screened Rooms

Many plants with older RF machines have been requi~ed to place the machines in a screened roo~ to preven trans= mission of signals outside the plant which interfere with police and fire department radios, as well as Citizen Band radio. Unfortunately, the workers operating these RF machines are also inside the screened rooms. This, of course, means that they are subjected to additional P..F exposure due to reflected RF waves o_ff the screened walls.

_g Shielding

The principle hazards in RF sealing operations include 1) exposure to RF radiation, 2) electrical arc burns, 3) thermal burnsp 4) crushing by the sealing jaws. The technology now exists to shield the jaws of RF sealers so that almost no personnel exposure to RF radia= tion occurs. Most RF sealer manufacturers offer shielding as an option for-their prodcuts. This shielding may add 10-50% to the cost of the sealer, and is usually not pro­ vided by American employers. Ironically, shielding is installed on all RF sealers exported by U.S. manufacturers to Eastern European countries in order to meet the stricter RF radiation protection standards in those countries. - 76 -

Induction Heaters

Conductive materials (metals, etc.) can be heated by applying alternating magnetic fields to t~e sample. This is called induction heating. It is use_d mainly for ___ _ - . -- - forging, tempering-, brazing, and soldering operations_. Induction heating equipment usually uses frequency_ rangers between 50 Hz and lOkHz. The current in the coil producing the magnetic field can be very large--5000 Amps· is not unusual. Swedish researchers have found that there is seldom - any whole body exposure on the part of the operators of induction heaters. However, there is often hazardous local exposure--for example, to the hands.

RF/MW Equipment in the Food Industry

RF dielectric heaters operating at 13.5, 27, or 40

MHz are widely used in the food industry. So are microwave ------ovens operating at either 915 MHz or 2450 MHz. - This equipment is used for such operations as finish drying of potato chips, precooking chicken parts, donut cooking, thawing frozen food, destroying mold in baked goods, cooking bacon, and opening oysters. There is an enormous variety of applications and operating powers in industrial RF/MW cooking systems. However, since virtually all· of this equipment is - 77 -

conveyorizedf with openings at the entrance and exit, operators may be exposed to high levels of RF/MW radia_tiono For example, one FDA survey showed leakage at the conveyor slot of an indus'trial microwave oven to be 70mW/cm.2 OSHA surveys should be undertaken in all food­ processing plants where RF/MW equipment is in use.

Protective Measures ·

There are some excellent protective measures in the new NIOSH proposals. These proposals have not gone into effect·, but they provide a fine guideline for programs that union members can recommend on their own. Here are a few of the NIOSH proposals that seem especially worthwhile:

Medical Examinations

Laboratory examinations should include: 1. Urinalysis and thorough blood analysis==i.e., white blood cell count, etc., as well as counts for trigly- · cerides and cholestrol. 2. Evaluation of iardiovascular function, including an electrocardiogram (ECG). 3. Evaluation of neurologic function, including an electroencephalogram (EEG). An emotional and behavioral profile should pay attention to such factors as weakness, headaches, memory loss, insomnia, and irritability. - 78 -

4. Medical examinations should pay particular attention to skin burns and damage to the eyes. Eye examinations should include use of the slit lamp to show injury to the past capsular surface 9! the_eye. NIOSH recommends that exposure t6 RF/MW levels greater than the permissable levels be followed within 3-7 days by a thorough medical examinationo Medical records including health and work histories - should be maintained for at least 30 years after employment ends for- all persons occupationally exposed to RF/MW radiation.

Labeling and Posting __,/

Areas in which RF/MW exposures have been determined .. to be at or above one half the permissable·level shall be posted. Areas in which RF or MW radiation exists at levels - above the recormnended guideline shall also be posted. In this case, the warning sign should read, HAZARD--DO NOT ENTER.

Informing Employees

An employer shall be responsible under the proposed NIOSH recommendations for informing all new and present employees of the techniques of monitoring for RF/MW radia­ tion, and of the potential biological hazards of being - 79 -

exposed to RF/MW radiation. Oral instruction supplemented by written material will be required. Qualified personnel must deliver the information.

Work Practices

Appropriate work practices should be prescribed to limit unnecessary exposure to RF/MW radiation. They ma.y including the following: l. Sources· of B:E/MW radiation shall be switched off when not being used. 2. Maintenance of generating or transmitting equipment shall be performed, whenever possible, while such equipment is not in operation. 3. Whenever possible, access to the vicinity of equipment producing RF/MW radiation above one half the permissable level shall be strictly limited to authorized personnel.

Engineering Controls

Shielding may consist of metal sheets, wire mesh, metallized fabrics, or metal-coated glass, plastic, or other materials. All shielding equipment should be pro­ perly installed and groundedo If not provided by the manufacturer, additions to equipment such as wavetraps, dummy loads, grounded curtains, - 80 -

- -- . -choke seals, and deflecting elements should be.:.:...installed, where necessary, to redirect radiation emitted from doors,. ports, slots, and other openings. Interlocks should be provided on all chambers or oven-type equipment to stop the generation of RF/MW radiation unless the chamber is sealed, and to shut.o~f such equipment automatically when the door is opened.

Monitoring and Record Keeping

Workplace areas in which the levels of RF/MW radia­ tion have been found to exceed OSHA limits should be

surveyed every 6 months. .../ If measurements taken during a survey indicate that occupational exposures exceed the recommended limit, a second survey shall be made on the next working day. If the limit is exceeded again, the use of all equipment pro-. ducing the excessive radiation shall be prohibited until appropriate controls have been instituted. All survey data sheets shall be maintained to show time and date of measurement, monitoring equipment used, names of employees and action taken. ,These data sheets shall be made available upon request to officials of HEW and OSHA, as well as employers and employees. - 81 -

Some Final Thoughts

Keep in mind that adequate regulations to protect you from RF/MW radiation are not yet in effect. Also keep in mind that during this entire century, the medical and scientific community in the U.S. has been woefully ignorant about the long-term biological effects of all kinds of electromagnetic radiation. Here in the U.S., we have just begun to be aware of the consequences of exposure to radiowaves and microwaves. Within the next 10=20 years, biological damage resulting from exposure to B:F(MW radiation may well pose a very seri= ous occupational health problem. Don't wait for the government to act! The whole history of occupational disease shows·us that the government is always years behind the disease and death toll of any harmful agent. Learn to protect yourself. Avoid exposure to RE/MW radiation whenever possible, both in and out of the workplace. Remember that what you can't see can hurt you. Insist that RF/MW equipment be turned off before undertaking repair or maintenance operations. Educate yourselves and the members of your locals about the known and potential health hazards of RF/MW

,, . _,· radiation. Way back in 1969, Allan Frey, one of the nation's leading researchers in the field of RF/WN bioeffects told - 82 -

an international conference that he took precautions to avoid RF/MW radiationo "I very carefully avoid exposure myself," Frey·saido

"._ o. I do not feel that I can take people into these (electromagnetic) fields and expose them and in all honesty indicate to them that they are going into some­ thing safeo" If such caution was gooa enough for a leading scien­ tist like Allan Frey, as far back as 1969, it is good·· enough for you today!

_.,,, - 83 -

. PART VI

LASERS

- .. :··: How Do Lasers Work?

The word laser stands for "Light Amplification by Stimulated Emission of Radiation." The name describes the physical principle involved in the production of the radi= ation~ This principle was discovered in 1916 by Albert Einstein, who predicted that if the energy-level of an atom or molecule was raised, its stored energy could be stimulated and released by subjecting the a.tom or molecule to a "shot" of electromagnetic radiation of the right frequency. Einstein's theory is applied in the laser in the following way. A tremendous flash of light, or other electromagnetic energy, is pumped into a closed system; such as a gas-filled tube or a solid ruby rod. When this happens, the electrons inside the atoms of the gas or-the

.. ruby become agitated and excited. Ea.ch excited electron then releases a photon (unit) of light-or energy that equals the "shot" of energy that hit it. Because of mirrors placed at either end of the gas-filled tube or ruby rod, these photons of energy begin to bounce back and forth along the axis of the closed system, stimulating

I - 84 -

other electrons to give off light. This process is called lasing. Finally, the increasing cascade of light being reflected between the mirrors is amplified to such an extent that it bursts through one of the mirrors as an enormously powerful laser beam. Hence the term "light amplication through stimulated emission of radiation." And, mind you, all this has taken place within a few thousandths of a second!

What Is Laser Radiation?

~, Not all lasers produce visible light. Many lasers give off invisible radiation in the infrared or ultra­ violet region of the electromagnetic spectrum. In order to better understand-laser radia~ion, however, it. is helpful to compare it to light. Ordinary light coming from the sun, or an incadescent light bulb, is made up of electromagnetic waves of many different frequencies. These waves are all jumbled togeth- er, and they are travelling in every direction possible. For this reason, ordinary light spreads out as it travels, and finally dissipates. Because of its lack of direction, it is called incoherent light. Laser light, or laser radiation, on the other hand, is coherent. Laser radiation is made up of electromagnetic = 85 =

waves of the sam~ wavelength and frequency, whish are travelling in unison in the same direction. -Thusjl instead. of f.anning out like light from a flashlight, las.er radia= :.:.tio:Q:travels in a straight and narrow, pencil-like beam for-incredibly long distances. Because the radiation in a laser beam is so qompact - and coherent, it has enormous power. In fact, it is by far the most pwoerful light on earth. For example, it can melt lead so that it runs like water. Indeed, it can vaporize any substance known to man. The sun emits about 6500 watts per square centimeter. Laser beams have been produced with a power of more than 500 million watts per square centimeter. When focussed in a tiny area, some laser beams can burn billions of times more brightly than the light at the surface of the sun!

- The History, Sources 1 and Uses of Laser Ra.di a tion

Einstein's theoretical explanation of controiled emis­ sion of radiation was not applied practically until 1951, when Dr. Charles H. Townes, of Columbua University, figured out a way to make a maser--Microwave Amplication by Stimu= lated Emission of Radiation. Dr. Towne actually constructed a maser in 1954. Ten years later, he shared the Nobel Prize in Physics with two Russian scientists, who had developed the maser independently and at about the same time. - 86 -

In 1958, Dr. Townes and Dr. Arthur L. Schawlow, of the Bell Telephone Laboratories, figured out a way to make a. las~~. The first laser was built in 1960 by Dr. Teordore H. Maiman, of the Hughes Aircraft Company. Dr. Maiman used a ruby crystal with the ends ground flat and silvered to make mirrors. Less than a year later, a gas laser was developed which used a mixture of helium and.neon. Today, gas lasers use many different gases in order to generate radiation of different wavelength and power out put. In addition to the helium-neon laser, some of the more common gas lasers use helium cadmium, carbon dioxide, argon, krypton, and gallium _,, arsenide. Unlike ruby crystal lasers, gas lasers are not triggered by optical pumping, but by radio waves. This enables the gas laser to be used in continuous wave (CW) operations, instead of in pulses as in the case of the ruby laser. In recent years, chemical lasers in which a mixture of chemicals initiates laser action have also been developed. Over the past 20 years, the development and manufacture of solid state and gas laser devices and systems has been phenomenal. The applications of lasers can be divided into two main categories: 1) commercial, industrial, military, and medical uses, and 2) scientific research. Lasers are = 81 =

now being used for a wide variety of purposes, including micromachining, welding, cutting, holography, seal-ing,---­ optical alignment, optical radar, photocoagulation, sur­ gery, surveying, and message transmission.

Alignment

The narrowness of the laser beam makes it. ideal for . operations requring precise alig:i:µnent. Perhaps the best known example of this is the two-mile-long linear acceler= ator at Stanford Unlversity, in California. Only a laser beam could carry out the incredibly dif.ficul t task of . keeping the 7/8 inch bore of the accelerator straight along its entire ,length. Laser beams are also widely used in tunnel-boring projects. Ordinary tunneling machines can drift as much_ as two to three inches every five miles. However, lasers can-guide the boring machines so that the deviation.is onl7 about 1/2 inch per mile!

Welding and Metal Cutting

By passing a laser beam through a lens system, extremely high power can be focussed in a very tiny area. Thus lasers are very useful for spot welding in which a precise and delicate connection is needed. Lasers are also invaluable for precision metal cutting. - 88 -

.. Laser beams have been used to cut concrete and steel, and to vaporize marble. They have also been used to cut holes in diamonds-~one of the hardest substances known to man.

· Communications

· ilt has,,, long· been realized that a single laser beam . couL

Medical Uses

Lasers have been used for many years to repair torn places in the retina of the eye. (The retina is a membrane of nerve cells lining the back of the eye. The cells of the retina detect light and send visual messages- to the

brain). By focussing weak pulses of laser radiation on a torn or detached retina, doctors can "weld" the membrane back into place. This process is called photocoagulation. Surgeons are using laser beams to seal off stomach bleeding, to repair obstructed arteries in the heart, to remove growths from vocal chords and polyps from the

_J - 89 =

in_testines, and to burn· away birthmarks and-ot"h:er_:_sltTn - blemisheso Dentists are using laser beams as painless tooth drillso

-Military Uses

Lasers are in widespread use in the Armed Forces ··· as range finders for various weapons. Lasers are also being used as optical radar to search for enemy missiles and satellites. Lasers are being developed by the Department-of Defense as "death ray" weapons_ capable of knocking missile~ out of the sky and of destroying enemy satellites in spaceo The Navy has tested a shipboard laser weapon that can destroy an enemy missile half a mile away. Laser-guided nsmart!V bombs were first used in Vietnamo Today, there are many such weapons. They·are known·as Precision Guided Munitions (PGMs).

Scientific Research

Scientists are experimenting with enormously powerfu~ lasers in the hope of creating cheap electric power. Laser fusion--a process in which laser beams achieve a thermonuclear burn--may one day be used to produce energy on a mass scale. - 90 -

Because a laser beam can maintain its concentra­ tion for thousands of miles, lasers are being studied for possible use in space-to-earth energy transmission. ' One problem with this scheme is that birds or animals passing through Laser Power Transmission System would be incineratedc

THE BIOLOGICAL EFFECTS OF LASER RADIATION

As already noted, lasers operate in the infrared, visible, and ultraviolet portions of the elec1ro.aagnetic spectrum. Since radiation must be absorbed to produce a biological effect, it is important to understand that the degree of injury from laser radiation depends upon the wavelength and power of the radiation, and the capacity of tissue to absorb radiation of that parti­ cular wavelength.

How Laser Radiation Injures the Eye (See Appendix E for diagram)

The body organ most susceptible to laser radiation injury is the eye. This is largely because the eye has the ability to refract, or magnify, long wavelength ultraviolet radiation, visible light, and infrared radiation in the region nearest to the visible light portion of the electomagnetic spectrum (called the near­ infrared.) ~ 91 -

The refractive system of the eye operates in this way: the cornea and lens~ which are located at the front of the eye, focus light and other radiation on the ret­ ina at the back of the eye. During this process, the .

power density of the focussed radiation can become- 0• - - - -

100,000 to 200,000 times greater by the time-it reaches-­ the retina.o Thus, if the eye were to be directly exposed to a laser beam of 5 milliwatts per square centimeter-- a level easily achieved by a small two-milliwatt helium neon laser-- the power level at the retina would be approximately 1000 kilowatts per centimeter squared! Such a large magnification factor obviously makes laser radiation extremely hazardous for the eye. Indeed, upon direct exposure to a laser beam, the ret- _-___ ina can be imploded (made to burst inward) resulting in complete loss of vision. And at lesser laser inten- sities, laser radiation can burn the retina, causing partial blindness. Some investigators have found retinal burns when the eye has been exposed to as small a quantity of laser radiation as one millijoule per centimeter squared in an 0.5 millisecond burst from a ruby laser. (Two units are generally used to measure the power output of las­ ers--joules and watts. A watt is a unit of power measur= ing the rate at which electrical work is being done. The. _ . _ . - 92 -

joule is a unit of energy measuring the total capacity to do work. One joule is equivalent to one watt applied for one second. It can also mean a 10-watt burst of laser light lasting 0.1 second, or a billion watts lasting a billionth of a second) .

. Infrared Laser Radiation

Most of the eye damage from exposur·e to infrared radiation occurs at the surface of the cornea--the trans­ parent layer at the front of the eye. When the cornea absorbs infrared radiation, it becomes heated. This can

cause cataracts to form in the front portion of the eye. ../. There is nothing new about infrared cataracts. They have been recognized as a compensable occupati:bnal dise·ase in the U.S. since 1907. Sometimes they are referred to as industrial heat cataracts because they were once common in the eyes of glass blowers, steel puddlers, and other workers exposed to the intense heat of infrared radiation. Today, protective goggles have markedly reduced the inci­ dence of such thermal cataracts.

Ultraviolet Laser Radiation

The effects of ultraviolet radiation are different from those of infrared radiation or visible light. Because it has less penetrating power, ultraviolet radiation is - 93 =

absorbed at or near the surface of tissues. For example, ultraviolet is a common cause of skin cancer. As for tlie eye, ultraviolet radiation mostly affects the outer= most layers of the cornea and the conjunctiva, which is the mucuous membrane that lines the inner surface of the eyelid. When the eye is exposed to ultraviolet, both the cornea and the conjunctiva can be injured. This conditio~ is called kerato-conjunctivitis. In addition to being ------caused by ultraviolet laser radiation, kerato-conjunctivitis can- result from the reflection of sunlight off snow ( snow. blindness), or by a welderes arc, or by a sunlamp. Acute kerato-conjunctivitis is easily diagnosed. There is extreme discomfort and a sensation of "sand" in the eye which may last for hours. However, the chronic form of kerato--conjunctivi tis often goes undiagnosedo The patient often goes thorugh life believing himself to be particularly sensitive to light and wearing tinted glasseso

Potential Laser Hazards

Solid=state lasers present the greatest hazard because of their high peak powers. Gas lasers are not as powerful, but they are still capable of producing radiation that can cause blindness and other permanent eye damage . . ·,/ Pulsed lasers present a special problem. For example, two pulses, neither of which is sufficient to cause damage - 94 - separately, may injure the eyes if the time interval between the pulses is short enough. Thus the possibility of cu:nulative damage must be considered. This is why high powered, short pulse (Q-switched) lasers can easily cause irreversible damage to the retina of the eye. (Q-switched lasers emit radiation in pulses which have a duration of only several billionths of a second). Many lasers designed for tactical military applications are either range finders or target illuminators. A great majority of these lasers are Q-switched. The most widely used Q-switched lasers are ruby lasers or neodymium (glass) lasers. Ruby lasers emit red light; neodymium lasers emit infrared radiation which is invisbile.

Reflections

The manner in which laser light or laser radiation is viewed is extremely important in determining how hazard­ ous it may be. There are three basic ways to view a laser beam. A person may view the original laser beam. Or he may view its reflec'tion from a flat, smooth, or mirror-like surface such as a windshield or a glass pane. (This is called a specular reflection, and it can have. the same power intensity as the main laser beam). Or he may view a dif­ fuse (scattered) reflection from a dull, non-glossy surface such as a piece of plain white paper. ---7

= 95 -

Direct viewing of a laser beam should·~--ot--course, be avoided at all costs. So should viewing the specular_ re­ flection of a laser beam from a smooth surface. Ordinarily, laser reflection from a dull- surf ace is. considered safe to view because the reflected radiation is sufficiently scattered so that it can no longer be focused to a point image on the retina at the rear of the eye. However, it is extremely important to know that this is not always the case! For example, if the eye can see the diffuse surface spot .size, the power density of the reflected--1-aser- beam-­ will still be capable of causing severe injury to the retina. This is a particular hazard with high powered lasers. Moreover, suc-h diffuse reflections are hazardous at all viewing angles. There are two very important points to remember about ·diffuse laser reflections: 1. The possiblity of an accidental exposure to diffuse laser reflection is many times greater than the probability of being exposed to the narrow direct laser beam. 2. The risk of harm from diffuse laser reflection occurs at all viewing angles ·and at all distances from the reflecting surfaces, provided that they eye is still able to resolve the diffuse spot. - 96 -

Optical Aids

Sometimes optical aids such as binoculars or micro­ scopes are used to view laser reflections. Such devices can greatly increase the power density of laser radiation directed to the retina of the eye.

Operator Hazards

·All personnel who work intimately with lasers, whether in an industrial, military, ·research, or medical setting, are subject to laser hazards. There have been several instances in laboratories in which an eye has been blinded by acute exposure to laser radiation. However, covert (hidden) exposures represent a much greater danger. First, the individual is not aware of being injured. Second, due to lack of awareness, he is apt to develop faulty work habits which can lead to repeated exposures. This is particularly true if an individual is exposed to laser-reflections. There may well be no visually detectable warning if this happens. And although the radiation intensity at the front part of the eye may be relatively weak--for example, measured in microjoules--the power of the radiation absorbed by the retina at the back of the eye can be highly injurious. = 97 -

How Laser Radiation Can Affect the Skin

Overexposure of the skin to laser radiation can cause mild reddening, blistering, or serious burns arid- charring,­ depending on the amount of radiation absorbed, it-s wave­ length, individual susceptibility, and duration of exposur~o Depigmentation of the skin and damage to underlying organs may occur from exposure to extremely high powered laser radiation, particularly from Q-switched pulses.

The Biological Uncertainties of Laser Radiation __

Most of the so-called laser exposure criteria have been based upon observations through an ophthalmoscope of lesions and burns on the retina of the eye. But irreversible visual performance changes in the eye have been noted after exposure to laser radiation levels much lower than those necessary to cause retinal burn. For example, in 1973, members of the U.S. Ariny Laser Safety Team at Frankford Arsenal, in Philadelphia, found that they could inflict considerable changes in the retinas of monkeys with low-level laser beams that were theorectically said to have only one chance in a thousand of doing any damage! This had been predicted by an ophthalmologist named Dr. Milton Zaret eight years earlier. Dr. Zaret is the - 98 -

same man who warned 20 years ago that microwave radiation could cause cataracts and other serious damage-to-the eyes. Because of these findings, great uncertainty exists - · · __ : about how much laser radiation exposure is safe. - Indeed, there is widespread agreement among medical.scientists that any proposed maximum permissable exposure (MPE) or threshold limit value (TLV) for laser radiation does not sharply divide what is hazardous from what is safe. In other words, we have the same situation with laser radiation as with radio-frequency and micrg}V'ave __ radiation_.______

It would be well to keep this in mind when we discuss j how to prevent harmful exposure to laser radiation.·

LASER SAFETY

The most desirable way to prevent harmful exposure to laser radiation is, of course, to locate the entire laser system in a closed room. This is done in many laboratory and industrial applications. When the laser cannot be enclosed, environmental con­ trols must be used. Backstops and shields designed to prevent the laser beam from irradiating occupied areas are often employed. Military laser firing ranges use natural terrain features such as mountains or thick forests as backstops. - 99 -

Protection of personnel can be accomplished either by making sure they remain outside of all potential laser beam paths, or by providing protective eyewear.

- _ Laser Protection Eyewear

It is extremely important to keep in mind that no one type of eyewear offers protection from all laser wavelengths. Consequently, great care must be exercised in the selection of eyewear that will screen out the desired laser wavelengths.

Many laser-using firms do not depend on safety g-lasses - to protect employee's eyes from laser beams. The point has been made that laser goggles or glasses may give the wearer a false sense of security, tempting him to expose himself to unnecessary hazards. If laser goggles or glasses must be worn, the supervisor

~f the laser operation should be responsible for providing the correct eye-protection equipment. Selecting such equipment requires knowledge of the laser power levels and wavelengths that can be expected at the eye during all phases of the laser operation. The American Conference of Governmental Industrial Hygienists (ACGIH) (an industry standard-setting group) warns that safety glasses should be periodically checked to make sure that they can screen out harmful laser wave= - 100 -

--lengths. Also, there should be periodic checking to see --that laser goggles are not being mistakenly used_to-pro- ,-tect a worker from different wavelengths of _laser radiation. Goggles and eyeglasses are available 1;0 protect-the eyes against nearly all laser wavelengths. -EaG~ _la.sei: _eye__ - _ - protection device is labelled with the optical.power density and the wavelength for which it is effective. Ordinary sunglasses should never be confused with laser safety eyewear. Sun glasses merely reduce _the -- light trans­ mitted to the eye by factors of less than ten, whereas laser safety eyewear may be required to reduce the light reaching the eye by thousands of times. If you must wear laser goggles or glasses, remember two things: 1. Make sure you know the optical power and wave= . length of the laser radiation to which you will be exposed. 2. Make sure that the same power and wavelength values are marked or labelled on the goggles or glasses you have been issued. Remember also that many lasers radiate-at more than one wavelength. Eyeglasses that protect against one wave­ length may be useless against another. This problem may be particularly serious with lasers that are tunable over broad frequency bands. - 101 =

The American National Standard for the Safe Use of Lasers

The .American National Standards Institute (ANSI) (another industry standard-setting group) has recomm~n~~d a standard to prov'ide reasonable and adequate guides for the safe use of laser systems with wavelengths between 200 nanometers to 1 millimeter (200 nm-1 mm). This is.some-

times written as 0.2 micrometers to l millimeter (0.2 um=l, mm). In this connection, it should be noted that a milli­ meter is one thousandth of a meter; a micrometer is one thousandth of a millimeter; and a nanometer is one thou­ sandth of a micrometer. It should also be noted that ultra= violet radiation wavelengths range from 200-400·nanometers (0.2-0.4 µm). The wavelength of visible light is between 400 and 700 nanometers (0.4-0.7 µm). And infrared radiation wavelengths range from 700 nanometers to one millimeter

(0.7 µm-1 mm).

Laser Device Hazard Classification Scheme

The ANSI standard includes a laser hazard classification scheme. In this scheme, laser devices are classified into four separate categories and appropriate control measures are specified for each one. The ANSI hazard classification scheme is identical to the one recommended by the ACGIH in its Guide for Control of Laser Hazards. - 102 -

The basis of the hazard classification scheme is the ability of the primary laser beam, or the reflected - - primary beam, to cause biological damage to the eye or the skin. Here are the 4 hazard classifications: 1. A Class I laser is one that is considered to be incapable of producing damaging radiation levels. It is, therefore, exempt from any control measures. 2. A Class II laser is a low-power laser system. Its beam may be viewed under carefully controlled exposure conditions. A Class II laser· must have a cautionary label affixed to the external surfaces of the device. 3. A Class III laser is a medium-power laser system. It requires control measures to prevent viewing of the direct beam or a specular reflection of the direct beam.

4. A Class IV laser is a high power system. It requires the use of controls which prevent exposure of the eye and the skin to the direct and diffusely reflected beam. Class II, Class III, or Clas IV lasers contained in a protective housing and operated in alo~r classification (Class I, II, or III) require specific control measures to maintain the lower classifications. - 103 -

Indoor Laser Operations

Indoor laser operations may take place in a ------class= ,,· ... --- .. ,.._. .. - ... - .•------~•: ·-c.:-"".:- ··:-·:,- ~ roomp machine shop, or research laboratory. Here are - ----~----- .. some recommendations by ANSI for evaluating Class -~III lasers used indoors in order to protect personnel of potential harmful exposure to laser radiation: 1. Evaluate the laser beam paths and determine the hazardous beam path. 2. Determine the extent of hazardous specular reflection (as from a smooth, flat, mirror-like, or lens surface). 3. Determine the extent of hazardous diffuse reflections. Hazardous diffuse reflections are possible from a focussed beam of a Class III laser. 4. Determine if any other (nonlaser) hazards exist. (See subsequent section entitled Associat~q~_t~r Hazards).

Outdoor Laser Operations over Extended Distances

Lasers are commonly used outdoors in mining ,_t~,q~l.§L, ---~~-;;·~·;"". in highway construction sites» in pipeline trench construc­ tion» and on military laser ranges. Here are the ANSI safety steps recommended for outdoor operations:

-~· 1. Estimate the nominal hazardous range of the laser. Remember that beyond a few hundred meters-·ti"ncerta.intie-! - 104 - arise from atmospheric effects, etc. Typical hazardous

. ranges from laser illuminators with large beam spreads . are often less t~an 100 meterso However, hazardous ranges for laser rangefinders with narrow, high-power beams may be from 5 to 50 kilometers! Backstops are obviously in order for such devices. 2o Evaluate potential hazards from §P~~ular re:-­ flections. Specular surfaces ordinarily encountered (for example, windows and mirrows in vehicles and windows in buildings) are oriented vertically and will usually reflect a horizontal beam in a horizontal plane. As much as 8% of the beam's original irradiance may be reflected back toward the laser from a clear glass window oriented perpendicular to the beam. If a beam strikes a flat specular surface at an angle, a much greater percentage of the beam's power can be reflected beyond or to the side of the target area. If the beam strikes a still pond or similar surface at a low angle, the power of the reflected beam may_a._lso_ be hi=g=h~--- 3. Determine whether hazardous diffuse reflections exist. 4. Evaluate the stability of the platform (vehicle, etc.) upon which the laser is mounted in order to determine the lateral range control and the lateral constraints that should be nlaced upon the beam traverse. 5. Consider the likelihood of people entering or being in -the area of the laser beam. - 105 =

control Measures for Laser Classifications

· 1. Class !=-These laser systems are exempt from all control measures and no warning labels are required. How= ever, any needless direct exposure to the eye should be avoided. 2. Class II--These low-power visible laser systems must have the warning label shown in Appendix H. 3. Class III--These are medium-power plasers requiring the following measures: a. Education and training of all persons using the ------~-----· laser. Such persons should be duly informed about the pot~n­ tial hazards of laser operations. b. Engineering controls. Appropriate safety mechanisms should be incorporated in the laser system. These may include beam stops, beam enlarging systems, en= clsoures, shutters, interlocks, etc. c. Laser Control Area. Consideration should be given to operation of laser devices in a controlled area in which the path of the laser beam is controlled.

-··~·- _- ... _.z.._ __ -- -···· d. Backstops. Laser beams emitted by Class III lasers should be terminated at the end of the useful beam path when the exposure level is greater than the Ma..~imum Permissible Exposure (MPE) for direct irradiation of the eye. e. Alignment Procedures. Alignment of laser systems (mirrors, lenses, beam deflectors, etc.), shall be - 106 -

performed in such a manner that the primary beam; or a

.. specular refl-ection of the primary beam, cannot directly irradiate the eye. f. Optical viewing aids. Optical-systems such· as lenses, telescopes, and microscopes may increase the hazard to the eye when viewing a laser beam. Special care must be exercised in their use. g. ~ye protection. Eye protection devices that are specifically·designed for laser protection should be used when engineering or procedural controls are inadequate to eliminate potential exposure in excess of the applicable ·\ MPE. h·. Warning labels. Class I I I lasers shall have warning labels with the appropriate cautionary statement affixed in a conspicuous place on the laser housing or the control panel, or both .

. i. Diffusely reflecting materials. In addition to beam backstops, shielding, and enclsoures, materials that will diffusely reflect any stray or incidental laser beams should be used in laser areas whenever possible. j. Keyswitch master interlock. Any laser designated as Class III shall be provided with an operative key master interlock or switching device. The key shall be removable and the device shall not be operable when the key is removed. - 10·7 -

.. -- ---~-,-- 4. Class IV-=High-power lasers and lase~ $f§t~m~~,----­ Such systems require more rigid controt--meas-ure-s--b-e~ainre------... -_---· there is a greater likelihood that-s-peeu~-a-!'-ref-l-ee-~ien--wil-1--­ have sufficient power to cause injury, and because of the greater risk of injury from diffuse reflection. The entire beam path capable of producing hazardous diffuse reflection should be controlled in a Class IV system. ·other recommended controls are as follows: a. Laser controlled area. Class IV laser devices shall be isolated in an area solely.designed for laser operations. Access to such an area shall require appropriate authorization. If the entire beam path of a Class IV laser is not enclosed, safety latches or interlocks shall be used to prevent unexpected entry into laser controlled areas. b. Enclosed beam patho Whenever possible, the entire beam path should be enclosed. So should the inter= action area--the area in which ir·x·aa1at'l-=on=o-"f--ma-~e-ri-a--ls=,cby===:.: the primary or secondary beam occurs. Enclosures should be equipped with interlocks so that the laser system will not operate unless such enclosures are properly installed. Whenever possible, c O Remote firing and moni taring'. the Class IV laser system should be fired and monitored from remote positions. d. Warning system. An alarm system or warning light visible through protective eyewear should be used prior to laser ac,tivation. A verbal "countdown" may also be used. - 108 - -··-...

e. Key switch master interlock. ·same as for Class III lasers.

Special Control Measures ·t·or Invisible Infrared Radiation

Particular care must be taken when using: infra.red laser systems. Many surfaces which appear to'be dull to the eye can act as reflectors of infrared. Thus·the beam from a Class III infrared laser should be terminated by a highly absorbent backstop. The beam from a Class IV infrared laser should be terminated in a fire-resistant material wherever practical. Areas exposed to reflections from Class III infrared lasers shall. be protected by screening with infrered absorb­ ing material . . In the case of Class IV infrared lasers, this material should be fire-resistant.

Special Controls for Ultraviolet Laser Systems

Exposure to ultraviolet lasers should be minimized by using shielding material to reduce the radiation to levels below the Maximum Permissible Exposure (MPE). Special attention should be paid to the possibility that ultraviolet radiation can produce agents that injure the skin, as well as ozone. - 109 -

Pulsed Lasers

There is widespread agreement that special caution should be exercised in the use of laser systems that can emit multiple pulses. More research may be needed to precisely define the MPE for multiple pulseso The con­ servative approach is to limit the power or energy in any single pulse to the Maximum Permissible Level specified for direct irradation at the cornea of the eye. This is the case with the ANSI and ACGIH standardso

Associated Laser Hazards

Many healt-J.1 hazards can develop indirectly or directly from laser operationso Here are some of them: * atmospheric contamination=-vaporized target material from high energy laser cutting, drilling, and welding may include asbestos, carbon monoxide, ozone, lead» ====----:_:-___-..;:::=- mercury, and other toxic agentso Know what the vaporized target material contains, and take appropriate protective measures. * ultraviolet radiation--such radiation can come directly or be reflected from flash lamps and CW laser discharge tubes, especially quartz tubing. * glare injury--this can occur with high luminance -~- visible radiation emitted by unshielded pump lamps. - 110 -

* cyrogenic coolants--such liqu±ds--cim -cause burns; examples are liquid nitrogen, liquid helium, and liquid hydrogen. * explosions--the hazard of explosions at the_ capacitor banks or optical pump systems exists during some.,. high-power laser operations. * X-rays--remember that hazardous--x-~r-adirtiun--· may be generated from high voltage (over 15kV) power.supply tubes. Know the voltage of power supply tubes i~ any laser system with which you work. Make sure these power tubes are properly shielded against X-ray leakage.

Medical Examinations

Personnel working with lasers should be divided into three categories by the Laser Safety Officer in charge of the laser installation: minimal risk personnel; mocterate­ ·risk personnel; and high-risk personnel. Minimal-risk personnel should have eye examinations for visual acuity prior to going to work with lasers. Moderate-risk personnel should have such examinations prior to laser·work, upon discharge from a laser environ­ ment, and immediately after any suspected laser eye or skin damage. This same medical protocol holds true for high-risk personnel except that these people should undergo eye - examination every three years while working with lasers. - 111 -

Maximum Permissible Exposure (MPE) Levels

MPE levels are set below known hazardous levels. Accoridng to ANSI, the MPE for infrared radiation is con= sidered to be well below the energy level required to produce a minimal lesion in the cornea. ANSI says that the MPE for ultraviolet radiation is well below the energy level required to produce redness, tearing, conjunctival discharge, and stromal haze. ANSI also claims that the MPE for visible minimal lesion on the retina, which means the smallest change in the retina which can be seen with an ophthalmoscope. Keep in mind, however, that changes in the retina due to laser exposure have been reported which are not visible upon examination with an ophthalmoscope. Remember also that medical scientists agree that the MPEs do not sharply divide a hazardous level of laser radiation from a safe one. If history holds true, and there is little reason to think it won't, the MPEs for laser exposure may well be lowered in the future. Therefore, it is good practice to maintain your own exposure levels as far below the MPE as possible. Appendix L gives the MPE for direct occupational exposure, interabeam viewing, from a laser beam. Appendix M gives the MPE for viewing a diffuse reflec­ tion of a laser beam or an extended source laser. - 112 -

Appendix N gives the MPE for skin exposure to a _.laser beam.

· Organizing ! Laser Safety Pr·ogram

_If laser operations are determined to pose potential health hazards to personnel, a Laser Safety Committee should be formed. ANSI recommends the following: The committee should include persons skilled in laser . technology and knowledgeable about laser hazards. The committee should establish and maintain adequate policies and recommendations for the control of laser hazards. A Laser Safety Officer--he may be a radiation protec­

tion officer or an industrial hygienist--shou.1-d irave- ·· authority to supervise the control of laser hazards . . _ -The Laser Safety Officer has the authority to suspend, .. restrict, or terminate the operation of a laser ~ystem if he decides that laser hazard controls are inadequate. The Laser Safety Officer alone should approve protect­ ive equipment (eye glasses, goggles, etc.), to be used for the control of laser hazards. The Laser Safety Officer should conduct surveys of all areas using laser equipment as frequently as he considers necessary. He will approve a laser system for operation only if he OPTIC . NERVE

FIGURE 1 STRUCTURE OF THE HUMAN EYE DIFFUSE LASER TARGET

Ft.AT LASER SPECULAR TARGET

CURV!O LASER SPECULAR TARGET

Figure 1. Reflections. The type of laser beam reflection often determines the extent of any hazard. FLAT SURFACE REFLECTION

MIRROR LASER

LASER

NOTE: r .. total beam distance from laser to eye wheni , • duect plus secondary.

Fig. B2 lntrabam Viewing-Specularly Reflected (Secondary} Beam

LASER

Fig. B3 Extended-SOmce Viewing - Normally Diffuse Reflection ( 1) Label for LOW POWER LASERS Only:

IUCR UCIGIIOUNO ~

HELIUM NEON LASER

DO NOT ST ARE INTO BEAM

1UC11 ._A .. I.ITTIII

(2) Label for MEDIUM POWER CLASS III a. VISIBLE LASER having a total power output below SmW but a maximum beam i.rradiance less than 2.SmW-cm0

nu.ow-- HELIUM NEON IQ LASER

00 NOT STARE INTO BEAM NEVER VIEW THAU OPTICAL INSTRUMENTS (3) Labels and Signs for MEDIUM AND HIGH POWER LASERS Only: (Blank format)

· (4) MEDll™ A.J.'ID HIGH POWER LASER Only: with sample hazard control inform~0 tion filed in) ·

Q SWITCHED RUBY LASER IUCR I.IT?IRS KNOCK BEFORE ENTERING-- ---·- ·-- Typical Laser Classification - Continuous-Wave (CW) lasen;

Wave!englh Class &0 Low-Poweu - Class II Medium-Powel!' - Class m lligh-Powelf - Clas1 IV Range Laser Waveienglh1 Exempt -

Ullraviolel CW Neodymium: ~0.8 X 10-9 W > CD211 0 bu& ~ O.S W >0.SW (I00-280 nm) Y AG (Quadrupled) 266 nm only for 8 hours

Ullra11iolel Helium-Cadmium llS nm only 6 > Class ff bui ~ O.S W >0.SW (3 RS-400 nm) Argon 3SU, 363.11 nm only ~ex ao- w lS0.7, 356.4 nm only } Krypton Visible llellum-Cadmlum 441.6 nm only (400-700 nm) Argon (Visible) ,U'J .9, 416,S, '8118, )> S 14.S nm, etc ~0.4 X 10-6W llelium-Selenium 460.4-700 nm only } X > CRsu ID bui S, 0.S W >0.SW (30 lines) > Class Hbui ~ R 13 rn- 3 w '... CW Neodymium: ~ YAG (Doubled) 532 nm ·- ~ ~ Helium-Neon U2.8nm .S,0.4X Co Krypton 647.H, 530.9, 616.4 nm, eAc } LI Near-lnrrared CW Galium-Aluminum 6 > Clasa I but ~ 0.S W >0.SW (0.7-Upm) Arsenide 8SO nm (20"C) ~ 80 X ao- W CWGalium W > Ciau I but ,s. O.S W >0.SW Auenide 90S nm (20"C) S, 0.1 X 10-l CW Neodymium: W > Clau I bul ,S. 0.S W >0.SW YAG 1064nm ~ 0.1 X rn-:i 3 > Class i but ~ O.S W >0.SW llelium-Neon B.08, USl µm only ~0.2 X 10- W far-Infrared Hydrogen fluoJide 4-6pm >0.SW (1.4-IOO pm) Carbon Monoxide S.0-S.S ,im ,S 0.8 X to-l W > C&ass I but~ 0.S W Carbon Dioxide 80.6pm } llelium-Neon l.19 µmonly Far-lnfoued Waler Vapor li8pm > Class i but < O.S W >0.SW ~ 0.1 W • I - ' (O.R-1 mm) liydrogen Cyanide 137 pm } laiger lhan exposures from lasting lo "max"' 8 l1ours (one wo1kday); otherwise Peiu:m8)A could be •Assumes no mechanical or eleclrical design incorporated Anlo Rase, syslem to prevent labulaled. .

I ,' Typical Laser OassificaUon - Single-Pulse lasen

Clasll IV Waveien.gih Exempt - C&au I Medium-Power - Class m High-Powe~ - Range Laser Wavcleng&h11 Pulse Dw-alion

Neodymium: YAG 1 • cm-2 Ultraviolet 9 No cdteda BO J )>... Q·-i;w (Quadrupled) 166 nm BO- 30 >< ao- , (Q-1w) 2 cm-1 9 i IOJ o cm- >!OJ• -0 3'81.i nm RO- 30 >< rn- , (Q-zw) No c1riieda Ruby (Doubled) ~., Visible Neodymium: Y AG 6 > 1S X rn-l J • cm-l 9s (Q-tW) ~ 0.2 x ao- J > CRr11s11 I but \l-. nm) (Doubled) 5:n nm } "- 20 X ao- 3 1 Ar (400-700 ~ 14 x no- J • cm- ,. Ruby 69<&.3 nm 2 1 4 >< 6 B > Cll2sa I buB >l.B J • cm- Ruby (Long Pulse) 694.l nm "'I>< ao- s ~ rn- ~:U J • cm-2 .,, Rftiodamlne 6G 6 • cm-1 6 < o 2 x no- J > Class I but > O.lB .5 nm s 1 (Dye Laser) 450-650 "'t x ur - . ~0.3i .» • cm- 1 9 6 J > Class I but > 0.16 J O cm- YAG 1064 nm "- 10 X 10- 11 (Q-sw) ~2 X rn- 2 Rnfoued Neodymium: ~ 0.16 J • cm- > BO J • cm-1 9 (Q-IIW) ~8 X 10-lj > Class I but Elft>lum: Glass 1.54 µm "- 10- IOO X 10-· 11 2 < 10-6 J -> Class I but > Dioxide 10.6 l'ffi B- 100 x ao- , (Q-sw) < Ciubon - ~ RO J • cm-2 "·

·1 I AMERICAN NATIONAL STANDARD Zl36.l-1976 Table S Maxbnum Permisuble Exposure (MPE) for Direct Ocular Exposmes. Inmbeam Viewing, from a Laser Beam

Exposure Duration, t Maximum Permissible Exposure and Measurement (s) (MPE) Notes for Calculation Uliiaviolit__ ·- _ 3 0.200-0.302 l0-2-J X 104 3 X 10- J • cm-l 3 0~303 10-2 -3 X 104 4 X 10- J • cm-2 3 0.304 10=2-3 X 104 6 X 10- J • an-l 2 1 0.305 10-2 -3 X 104 1.0 X 10- J • cm- 1 2 0.306 10-2-3 X 104 1.6 x 10- J • cm- 4 0.307 10-2-3 X 10 2.5 X 10-l J • cm-2 1-mm limiting apertuie 1 4 0.308 10- -3 X 10 4.0 X 10-l J • cm-l In no case shall the total imldiance, over all 1 X 10-l J • ·cm-'2 0.309 10- -3 X 104 6.3 the wavelengths within the UV spectral 2 1.0 X 10-l J • cm-l 0.310 10- -3 X 104 region. be greater than 1 watt per sqwue 1 4 l.6X 10-l J • cm-1 0.311 10- -3 X 10 centimeter llt)On the cornea 0.312 10-2-3 X 104 2.5 X 10-l J • cm-l 1 0.313 10-2-3 X 104 4.0 X 10- J • cm-l 0.314 10-2-3 X 104 6.3 X 10-l J • cm-1 9 J • cm-2 0.31.S-0.400 10- -10 O..S6 rl/4 1 0.31.S-0.400 10-103 l J • cm- 0.315-0.400 103-J X 104 1 x 10-3w. cm-l Visible and Near-ln!rued • 7 0.400-0.700 10-9-1.8 X 10-5 5 X 10- J • cm-l 4 3 0.400-0.700 l.& X 10-5-10 1.8 t31 X 10- J • cm-l 3 1 0.400-0..SS0 10-104 10 x 10- J , cm- 3 4 3 · 0..SS0-0.700 10-T1 1.8 r / X 10- J • cm-l Ce X 10-3 J • cm-2 0.550-0.700 T1-llr 10 7-mm limiting aperture 6 0 2 0.400-0.700 104-3 x 104 . Ce x 10- w cm- 7 See 8.5 for correction factors 0.700-.1.059 10-9-1.8 X 10-5 5 CA X 10- J. cm-l 0.700-1.059 1.Sx 10-5-103 l.8CAr3/4x 10-31-c:m-l 1.06()...1.400 10-9-S X 10-5 5 X 10-6 J • cm-2 3 4 1.060-1.400 5 X 10-5-103 9 t 1 X 10-3 J • cm-l 6 0 0.700-1.400 103-3 X 104 320 CA X 10- w cm-l Far-Infrared 2 2 1.4-10~ 10-9-10-1 ur J • c:m- 4 1 See Table 9 for apertures 7-10 0.56 r1/ J • c:m- 10- 2 See 8.6 for correction factors and Fig. 6. >10 O.lW• cm- }

•See Fig. 4 for graphui..~esenution. NOTES: ' CA• CFa.s.2 of Fig. 8 Ca • l for X = 0.400-0.SS0 .iim (see Fig. 9) Ca • IOI 15(;\- 0.550)1 for l\ • O.SS0-0.100 .iim .iim (see Fig. 9) T1 • 10 s for;\ .. 0.400-0.S50 Ti= t0x 101 20(X-0.5SO)I forxa0.550-0.700.iim . I .\ 'I' i••" . "' ......

AMERlCAN NATIONAL STANDARD Z136.H9'76

- +1ih, Maximum Permissible Exposure (MPE) for Viewing a Diffuse Reflection ndfld Source user

Wavelength. A. Exposwe Duration, K Maximum Permimlllti Exposure (µm) (s) (MPE) Not~ for Calculation and Meuumuent

lllttaviolet 0.200-0.302 10=2-J X 104 3 X 10-l J • c:m=2 0.303 10=1-3 X 104 4 X 10-J J • cm-2 0.304 10=2-3 X 104 6 X 10-J J • cm=l 0.305 10-2 -3 X 104 1.0 X 10=2 J •· cm=l 0.306 10-2-3 X 104 1.6 X to=l J • cm-2 0.307 10-2-3 X 104 2.S X 10=2 J • cm-l 0.308 10-2-3 X 104 4.0 X 10-l J • cm=2 2 4 2 0.309 10- -3 x 10 6.3 X 10-l J • c:m- 1-mm limiting aperture 0.310 10-2-3 X 104 1.0 X 10-l J • c:m-l 0.311 10-2 -3 X 104 1.6 X 10-1 J • cm-l 0.312 10-2-3 X 104 2.5 X 10-1 J • cm=2 0.313 10-2 -3 X 104 4.0 X 10-I J • cm=l 0.314 10-2-3 X 104 6.3 X 10-I J • cm=l 0.315-0.400 10-9-10 O..S6 11/4 J • cm=l 0.3 l.S-0.400 10-103 1 J • cm-2 0.315-0.400 103-3 X 104 1 x 10-3w, cm=2 Visible"' 0.400=0. 700 10-9-10 . 10t113 J. cm-2 • sr--1 0.400=0..SS0 10= 104 21 J • cm-2 • sg,=l 1..mm limiting aperture or czmin, whichever 3 - ) 0..SS0=0.700 10-Ti 3.83 , /4 J • cm-2. sr-1 isg:eata'

O 2 1 0.55()...0, 700 r1-1a6 21 c8 J cm- • sr= See 8..S for correction factors and Fig. 7 0.400-0. 700 104-3 X 104 2.1 Cat 10-lw. cm-2. sr-1 Neu lnC!.'3Ked 0 0. 700-1.490 10-9-10 10 CA t l/3 J • cm-2 • sr-1 l•mm limiting aperture or ~min, whichever 0.100- 1.400 10-103 3.83 CA r3/4 J • cm-2 • sr-1 is greater 3 4 2 1 a. 100-uoo 10 -3 X 10 0.64 CAW• cm- 0 sr- } See 8 •.S for conec:tion factors and Fig, 7 Fu-Infrued l.4=103 10-9-10-7 10-l J • cm-2 9 for :ipertutes 10-1 -10 0.56 rl/4 J • c:m-2 Si!ie Table 6. >10 0.1 W• c:m- 2 } Sell !U for correction factors and Fig.

•see Fig, 7 for graphic presentation and Fig. BJ of Appendix B. NOTES: CA'" CFa.s.2 or Fig. 8. Ca• I for"-• 0.400-0.SS0 1,1m (see Fig. 9) Ce "' 10I I S(>.- O.SSO)I for"-= 0.5S0-0. 700 ~m Ti • 10 s for A.., 0.400-0• .SSO "'m (see Fig. 9) r 1 "' 10 x 10ilO(A. • o.sso)J for A."' o..sso-o.7001,1m

-· ; . .. , .. ! \., -·· ·,.

AM£RJCAN NATIONAL STANDARD Zl36.1·1976

Table 7 Maximum Permissible Exposure (MPE) for Skin E."tposure to a user Be:im

Expaswe Duration. t Muim11m Permissible Exposwe Wavelength. ~ Notes for C.ilc:ulation and Masurement (Jim) (s) (MPE)

Ultraviolet 4 X J • cm-l 0.200-0.302 10-1 -3 X 10 3 10-l 3 . 0.303 10-1 -3 X 104 4 X 10- .J • em-l 1 4 X 3 J • c:m-l 0.304 10- -3 X 10 6 10- 4 O c:m=l 0.305 10-1 -3 X 10 1.0 X 10-l J 1 4 X 10-l J • c:m-l 0.306 10- -3 X 10 1.6 1 4 J • cm-l l•mm limiting aperture 0.307 10- -3 X 10 1.5 X 10-l 4 • c:m-l tobl iriadi3nce. over all 0.308 10~1 -3 X 10 4.0 X 10-l J ln no case shall the 4 • cm-l w'ithin the UV spect.raJ 0.309 10-1 -3 X 10 6.3 X 10-l J the wawlengths 1 4 X 10-I J • c:m-l than l watt per sq\We 0.310 10- -3 X 10 l.0 region. be greater 4 O 10-1 -3 X 10 1.6 X 10-l J cm-l c:entimeter 11pan the cornea 0.311 1 4 X J O c:m- 0.312 10-1 -3 X 10 2..5 10-I 1 4 1 J O cm-l 0.313 10- -3 X 10 4.0 x 10- 10-1 -3 X 104 6.3 X 10-l J • .cm-l 0.314 4 1 10-9-10 0.56 r1/ J • cm- 0.315-0.400 1 0.315-0.400 10-103 1 J • cm- 3 0 1 0.315-0.400 103-3 X 10" 1 X 10- W cm- Vm"'ble and Near•lnfnred \.. - 7 2 1 o.4-1.4 10-9- ur l X 10- J • cm- 1 4 O 1 aperture 10-7-10 1.11 / J c:m- 1-mm limiting O.;?Wo c:m-1 } 10--3 X 104 Fu-lnfnred 3 9-10-1 10-1 J. c:m-1 1.4-10 10- :iperture for 1.4 ta 100 ~ 7 0.56 11/4 J • c:m-1 l•mm limiting 10- -10 aperture for 0.1 to l mm 0.!Wo c:m-1 } · l l•mm limiting >10

5 5 - 4- 4 14""' ...oi ~ C: 3 3 0,_ c.:i < "" z 2 2 -2