Designed with Your Convenience in Mind Topic 1

Physics & Health Effects of Radon & RDPs

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Course Description – Designed with Your Convenience in Mind • Course Based Upon: • EPA, Indoor Radon & Radon Decay Product Measurement Protocols, July 1992 • EPA, Protocols for Radon & Radon Decay Product Measurements in Homes, June 1993 • EPA, Radon Mitigation Standards, April 1994 • EPA, Home Buyer’s and Seller’s Guide to Radon • EPA, A Citizen’s Guide to Radon •Audio Portion • Audio Sections that follow manual • Tone between each page of manual • Guest speaker interviews • Playable in music CD-players (car, home entertainment system or computer) • Streaming Videos on Web Site • Visual clips of unique elements • Show common measurement devices • Animation sequences • Resource Materials Online • Protocols, model contracts, EPA documents and many other tools to support you • Homework & Quizzes Online • Quizzes online www.certi.us • Access CERTI Education site with username and password provided when course was obtained. • Automatic feedback on questions • Course Completion Certificate downloadable upon completion of Online Quizzes. Note to Canadian Students: Please make sure you complete the Canada Specific Information Section of the Course.

1 Physics & Health Effects of Radon & RDPs

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Key Points: • Radon is naturally occurring • Radon is a chemically inert gas • Radon comes from the radioactive decay of uranium 238 • Radon comes from the immediate decay of radium 226 • Much of the radon produced enters the atmosphere • The concern with radon is when it enters a home • Radon can enter all types of buildings, including schools and workplaces • Radon comes from the area directly beneath building and a few meters around it, so it is very localized • Some of the radon that enters a home also leaves through windows and other openings to the outdoors - the concern is when it accumulates in a home. • Tight homes do not cause radon • Although radon can come from man-made situations like landfills or use of radium containing building materials, the vast majority comes from the soil

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Key Points:

• Vacuums or negative pressures within a building cause radon laden soil gases to enter from the soil beneath a home. • Vacuums are caused by either temperature induced stack effects or mechanical exhaust systems. • Temperature induced stack effects occur when the outdoor air is colder than indoor air. The colder outdoor air is more dense and will move down through the soil and push ahead of it the warmer, less dense air inside the building. As this air moves through the soil, it will pick up soil gases such as moisture and also radon. • Exhaust fans that take air out of a building can also draw radon laden soil gas into the structure. • The combination of temperature induced stack effect and mechanically induced vacuums will draw radon laden soil gas in. • All buildings can exhibit interior negative pressures relative to the soil. • If radon is being produced in the soil beneath the home where the negative pressures are being exerted, radon can enter. • Changes in these negative pressures will change the rate of radon entry, from hour-to-hour, day to day and from season to season as a function of how the interior pressures change. • Pressures in the soil from wind can also push radon in. • Since radon is a single atom, it can come through the smallest of openings in the foundation. • Since all foundations have openings, all types of foundations are susceptible to radon entry. • All types of homes, unless totally suspended (tree-house), can have radon concerns.

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Key Points

• Radon enters the interior air space of a building. • Radon is an unstable atom and will break down into a family of elements called radon decay products. • Since radon is in the air, the radon decay products formed will also be in the air. • Radon decay products have electrostatic charges. • When you inhale you will breathe in both radon and radon decay products • The radon is exhaled • The radon decay products will stick to the lung tissue • Before your lungs can clear the radon decay products, they can further break down and irradiate the lung tissue.

It is the radon decay products that actually present the health risk associated with radon gas.

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Key Points

• Radon and radon decay products release radiation • Alpha: A particle made up of two protons and two neutrons that flies out of the nucleus of an atom at about 50% the speed of light. • Very damaging due to mass and speed! • Beta: A small particle the size of an electron that is ejected from the nucleus. • Limited damage due to small size. • Gamma: Essentially a light wave. • Minor damage, per single release.

• Alpha particles are released when radon and two of its decay products (Polonium 218 and 214) decay. • The alphas from the decay products (rather than from radon) are of the largest concern because they can be released while the decay products are in the lungs. • Alphas can be absorbed by a piece of paper or the dead cells on the outside of our bodies. • That does not mean they cause small damage, but rather their size is so large that the probability of impact is very high. • Lung tissue does not have a thick protective coating, which is why the effect from radon exposure is believed to be lung cancer rather than skin cancer.

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Key Points

• Radon decay products release alpha particles • Polonium 218 & Polonium 214 • Alpha is very damaging if it hits a live cell • Lung cells are most susceptible because radon decay products are concentrated in lungs and cells do not have a protective covering like skin. • What happens when an alpha particle hits a lung cell? • Cell can die – okay since body can replace • If alpha hits DNA within cell’s nucleus, the DNA can be damaged • Direct hit • Chemical attack by ions formed by alpha particle strike. • Cancer suppressant gene impact • Cell loses defense mechanism against cancer • Defect can be passed on • Increases potential of lung cancer • Probability • Function of number of hits and amount of time

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Key Points

• Potential for radon induced lung cancer is a function of: • Amount of exposure • Time exposed

Analogy - Like a blindfolded person throwing darts at a dartboard • Probability of hitting bulls eye is a function of: • How many darts thrown at a time (from one to a handful) • How long the person continues to throw darts • Linearity: • Probability equally weighted between number of darts thrown (radon activity in building) and how many throws the person makes (time of exposure) • No threshold: • Although unlikely, the person could hit bulls eye with the first dart • The only safe level of radon exposure is when there is no radon (take the darts away from the person)

Graph shows excess lung cancer risk over norm (vertical axis) with increasing exposure in terms of radon decay product exposure x time (the working level month is explained in more detail later). Data based on occupational studies of miners with indication of where some home exposures fall on graph.

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Key Points

Radioactive decay is the natural process that an unstable element goes through to reach a stable configuration. • Alpha Release (α): • Atom loses two neutrons and two protons. • Since number of protons define the way an atom reacts with other elements to form molecules, a reduction in number of protons causes the atom to act like another element. • Atomic mass changes since number of particles in atom are reduced by 4. • Very massive and very damaging. • Beta Release (β): • Beta is an electron shot out from nucleus when a neutron changes into a proton. • An increase in number of protons causes atom to behave like another element. • Small mass and causes smaller damage than alpha particle. • Atomic mass does not change because the total number of neutrons and protons within nucleus stays the same. • Gamma Release (γ): • Whenever an alpha or a beta is released, the atom goes to a lower energy level. • The energy released is in the form of gamma which is a light wave. • Some detectors measure gamma as a means of measuring radon activity. • Little damage per individual release.

  +1P +1P Rn-222

Pb Bi Po At Rn As atoms decay, energy is 82 8384 85 86 released in the form of gamma, like balls making Po-218 sound as they drop through a pin-ball machine. -2 P -2 P Pb-214 -2N Since radon decays more -2N   slowly than radon decay Bi-214 The diagram shows how atoms move down the products, the rate of radon periodic chart as they lose protons from alpha decay is controlling Po-214 (aka: Secular equilibrium). decay and back up the periodic chart as they Pb-210 gain protons with beta decay. Gamma is released with each type of decay.

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Key Points

• When either alpha, beta or gamma is released they collide into other atoms. • Impact of radiation knocks electrons off of other atoms. • When an atom loses electrons it is referred to as an ION. • An ion has a different number of negatively charged electrons than charged protons. • Because of imbalance, an ion has a charge. • Ions are very reactive and can cause damage. • The concern of radon exposure is because it produces Ionizing Radiation.

More ionization occurs as alpha particles travel through air than from gamma or beta. The importance of Radon and Radon Decay Products creating ions is: • Ions cause damage • Many radon or radon decay products measurement techniques measure the amount of ionization as a means to estimate radon or radon decay product activity levels.

Note: A key report discussing the health effects of radon is titled: The Biological Effects of Ionizing Radiation (BEIR).

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Key Points When radon breaks down, there is a recoil from the released alpha particle. This causes the atom (which is now Polonium-218, a radon decay product) to be kicked backwards where some of its electrons will be knocked off -- causing the resultant radon decay product to have an electrostatic charge. • Radon Decay Products: • Act like solids • Have electrostatic charges • Will readily stick to other things • Dust particles (still suspended in air) • Walls or ductwork (no longer in air and cannot be dislodged) • Equilibrium Ratio (or Equilibrium Factor): • Defined as percentage of decay products produced that remain in the air. • Total number of decay products produced is a function of radon activity. • Percentage of radon decay products decreases as radon decay products attach to fixed objects – this is called plate-out. • Decreases with: • Increased air circulation • Fewer particulates in air • Increases with: • Stagnant air • More suspended dust or particulates in air • Range in homes: 30-70% • Assumptions: • EPA prior to 2003 and current NRPP & NRSB assumptions: 50% • Europe and EPA after 2004: 40%

As ER decreases, the health risk exposure decreases with the same radon gas level As ER increases, the health risk exposure increases with the same radon gas level

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Key Points • pico-Curie/Liter (abbreviated: pCi/L) • Measure of radioactivity typically used for radon gas in the United States. • Curie: radioactivity released by 1 gram of radium • Named after Madame Curie • A lot of radioactivity! • pico-Curie: one-trillionth of a Curie • 2.2 disintegrations per minute • Liter: a volume of air or water within which the amount of radiation measured is being emitted. • 1 pCi/L = 2.2 disintegrations per minute per liter of air or water. • Benchmarks: • Average outdoor level: 0.4 pCi/L • US EPA guidance level for long-term exposure: 4.0 pCi/L • Average indoor level in the US: 1.3 pCi/L • Other Units: • Becquerel/cubic meter (Bq/M3) is the unit used within the scientific community that expresses the same thing as pCi/L. • To convert: 37 Bq/M3 = 1 pCi/L • 4 pCi/L = 148 Bq/M3 • pCi/g • Sometimes radioactivity is measured in material like rocks or soil, in this case the radioactivity would be expressed in terms of activity per unit mass, such as pCi/gram or Bq/gram. • Soils over which homes are constructed where indoor radon levels are elevated are often in the 2-6 pCi/g range but certainly higher concentrations can be found, especially in areas where uranium mill tailings have been used as fill.

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Key Points

• Working Level (abbreviated WL) • Measure of radioactivity typically used for radon decay products in the United States. • Definitions: • 1 working level is the energy emitted from the short-lived radon decay products produced from 100 pCi/L of radon. If a room was maintained at 100 pCi/L of radon and no plate-out occurred then the activity level of radon decay products within the room would be 1 Working Level (WL) • 1 WL is 130,000 million electron volts of energy • Comes from the level of activity that miners were working in. • Benchmarks and Conversions • Primary Guidance: 0.02 WL • Federal standard for indoor exposure used in clean-up operations: • 40 CFR - CHAPTER I –Part 19 § 192.20 Guidance for implementation • US EPA action level for indoor air • Note some publications currently under review suggest 0.016 WL*. Miscellaneous: • Scientific notation: • 1 WL = 20.8 µJ (microjoules) alpha energy per cubic meter (m3) air

*Note that EPA publications after 2006 have cited 0.016WL instead of 0.02 WL

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Key Points • The equilibrium equation is an easy means to interrelate radon and radon decay product measurements. • The “pie-chart” provides an easy way to manipulate the equation. • If you do not know what the equilibrium factor is, assume 50% in accordance with the US EPA protocols and note that assumption in your calculations.

Example One: Calculate how much radon gas would have to be in a room that would result in the EPA guidance of 0.02WL of radon decay products, assuming a 50% equilibrium factor. Rn = WL x 100/ER = 0.02WL x 100/.5 = 4.0 pCi/L Note: This is how the original 4.0 pCi/L gas guidance was determined from the initial 0.02WL guidance.

Example Two: Calculate the amount of radon decay products in a room at 10 pCi/L where the equilibrium factor was known to be 40%. WL = ER x Rn/100 = 0.40 x 10 /100 = .04WL Note: Express the ER as a decimal, for example 40% = 0.4

Example Three: Calculate the equilibrium ratio in the case where the radon was simultaneously measured with the radon decay products with the following results Radon = 6 pCi/L and RDPs = 0.01WL ER=100 x WL/Rn = 100*0.01/6 = 0.167 which is rounded up and expressed as a percentage with the result of 17%

What would cause such a low equilibrium ratio?

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Key Points • Working Level Month • A measure of the actual exposure and hence risk for radon induced lung cancer. • Combines: • How many radon decay products to which you are exposed • How long you are exposed to them • The product of time and exposure • Month defined as 170 hours which is the average number of hours a person works in a month • Comes from methods for calculating occupational exposure. WLM = RDPs (WL) x Hours of exposure/170

Example: A person living in a home for one year, 75% of the time at 0.02 WL. WLM = 0.02 x 365 days/year x 24 hr/day x .75 = 0.77 WLM 170 hr/month

Note: If a person lived in this same house for 70 years their accumulative exposure would be 70 x 0.77 = 54 WLM which is a level where many lung cancer cases from uranium miners were observed.

Miscellaneous: • Scientific papers use the term Sieverts instead of WLM • 1 WL = 5 milli Sieverts (mSv)

Note: Since the WLM is the product of time and exposure, equal weighting of risk is given to the level of exposure and the time of exposure. Therefore, a person living in a home at 20 pCi/L for 1 year has the same risk as someone living in a home for 10 years at 2 pCi/L.

Person A: 20 pCi/L x 1 year = 20 Same risk of radon induced lung cancer Person B: 2 pCi/L x 10 years = 20

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Key Points • EPA has distilled risk estimates in easy to understand consumer documents • Let these documents provide interpretation for individual decisions • Higher risk for smokers than never smokers • Risk chart reproduced below for 2002 Guide as well as EPA’s 2003 Reassessment of Risk • Example: at 4 pCi/L EPA a “never smoker’s” risk is 7 out of 1000. • Compare this to other compounds that are regulated at a rate of 1 out of 1,000,000! • Radon is a major cause of lung cancer among non-smokers. • Risk is linear with exposure, zero risk at zero radon/radon decay products • Available for download at http://www.epa.gov/iaq/radon/pubs/ • See summary of EPA’s reassessment in appendix of student manual

Lifetime risk of radon induced lung cancer per 1,000 people exposed 2002 Citizen’s Guide EPA Reassessment 2003 Never Never Radon Level Smoker Smoker Smoker Smoker 20 pCi/L 8 135 36 260 10 pCi/L 4 71 18 150 8 pCi/L 3 57 15 120 4 pCi/L 2 29 7 62 2 pCi/L 1 15 4 32 1.3 pCi/L 1 9 2 20 0.4 pCi/L <1 3 3

400

300 Smoker 200 Never Smoker Risk/1000 100

0 0 5 10 15 20 25 Lifetime Average Radon Exposure (pCi/L)

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Reading Assignment: US EPA’s Citizen’s Guide to Radon

Key Points • Radon is a naturally occurring element that comes from the radioactive decay of uranium • Radon is a chemically inert gas that can enter a building from the soil beneath it due to negative pressures in the home or pressures in the underlying soil. • One cannot see or smell radon. The only way to measure levels is to test for it. • Radon breaks down into radon decay products that can be inhaled. • Radon decay products act like solids and have electrostatic charges that cause them to stick to lung tissue. • Polonium 218 & 214 release alpha particles that can damage the lung cells. • Alpha particles deliver 20 times more impact than do gamma and beta releases. • Prolonged exposure to radon decay products can increase the potential for lung cancer. • Radon decay products can easily attach to fixed objects, thereby removing them from the breathable air space. The percentage of radon decay products in the air relative to the total formed from the radon gas is referred to as the Equilibrium Ratio or Equilibrium Fraction. This percentage is dependent upon air movement and dust particles in the air, but is generally assumed to be 50% according to current protocols. • The health risk associated with radon exposure has been determined by first investigating dose response relationship for uranium miners, and secondly for residential exposures. • Exposure to radon represents a significant portion of the radiation exposure to which the general public is exposed. • The risk from radon is believed to be directly proportional to the amount and time of exposure, with no exposure other than zero having no risk. • Radon is considered to be a Group A carcinogen. That is, it is known to cause cancer in humans. • The US EPA recommends that people not have long-term exposures of more than 0.02WL of radon decay products or 4.0 pCi/L of radon gas, but risks still exist at levels below these.

Reading Assignment: US EPA’s Citizen’s Guide to Radon

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