The Soldier and the Industrial Base Chapter 11 Carbon Monoxide
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Carbon Monoxide Chapter 11 CARBON MONOXIDE TIMOTHY B. WEYANDT, M.D., M.P.H.* AND CHARLES DAVID RIDGELEY, Jr., M.D., M.S.† INTRODUCTION TYPICAL SOURCES OF EXPOSURE Steel Manufacturing Combustion Engine Exhaust Methylene Chloride Smoking MILITARY EXPOSURES World War I: Combat Mining Operations World War II: Tank Warfare The Modern Era: Armored Fighting Vehicles Military Aviation Household Heating PATHOPHYSIOLOGY OF EXPOSURE Carbon Monoxide’s Hemoglobin-Binding Affinity Carboxyhemoglobin and Oxyhemoglobin Dissociation HEALTH EFFECTS Autopsy Findings Signs and Symptoms of Carbon Monoxide Poisoning Staging of Signs and Symptoms Exposure and Muscular Exertion Central Nervous System Effects Circulatory Effects Chronic Effects DIAGNOSIS AND TREATMENT Clinical Diagnosis Treatment HEALTH STANDARDS Occupational Safety and Health Administration American Conference of Governmental Industrial Hygienists Committee on Toxicology Military Standards MEDICAL SURVEILLANCE SUMMARY *Director, Occupational Health Program, Pennsylvania State University, University Park, Pennsylvania 16802; Lieutenant Colonel, U.S. Army (ret); formerly, Medical Advisor for Clinical, Occupational, and Environmental Health; U.S. Army Biomedical Research and Development Laboratory, Fort Detrick, Maryland 21702-5010 †Lieutenant Colonel, U.S. Army; Occupational Medicine Physician, Occupational and Environmental Medicine Division, U.S. Army Environmental Hygiene Agency, Aberdeen Proving Ground, Maryland 21010-5422 397 Occupational Health: The Soldier and the Industrial Base INTRODUCTION Carbon monoxide is a colorless, odorless, taste- Many of the effects of what we now recognize as less and nonirritating gas formed as a by-product in carbon monoxide poisoning were discussed in an- the incomplete combustion of carbonaceous materi- cient literature. During the Middle Ages, these effects als. Frequently, but not reliably, the presence of were sometimes considered to be the work of demons carbon monoxide is accompanied by the odor of un- and witches. Some of the worst workplace exposures burned organic matter or fuel.1 Because of its high occurred during the 19th and early 20th centuries, inherent toxicity and extensive exposure potential, when industrial miners were frequently overcome by carbon monoxide has historically been considered not “white damp,” a term applied to the “inodorous na- only the most widespread poison known but also the ture” of carbon monoxide and associated products of most significant toxic gas in the workplace.2 Human partial combustion.2 Miners were often exposed, with exposure to carbon monoxide has been estimated to frequent severe or fatal sequelae, after mine fires, account for approximately 2,300 suicides and 1,500 explosions, and blasting operations. accidental deaths annually (ie, more than one-half the Serious exposures have been reported in much less yearly poisoning deaths in the United States). In addi- dramatic contemporary situations when individuals tion, an estimated 10,000 patients per year seek medi- have used contaminated sources of compressed air for cal attention because of exposure to this chemical.3 diving or positive-pressure respirators for industrial Fig. 11-1. These workers are testing new 75-mm howitzer tubes for the U.S. Army at the General Electric Plant, Erie, Pennsylvania, in June 1941. Such indoor testing, without adequate ventilation, quite likely exposed these workers to hazardous levels of carbon monoxide. Under today’s standards, a powerful, frequently monitored indoor ventilation system would be required. Photograph: Courtesy of the US Army. 398 Carbon Monoxide operations.1 Exposures in the home or workplace may gasoline-powered generators are operating, and in- occur in poorly ventilated areas when using improp- door firing ranges. Military industrial exposures are erly adjusted or inadequately vented heaters, kitchen possible during peace and war and can occur during stoves, water heaters, or charcoal braziers. maintenance and repair of internal combustion en- Army field exposures commonly occur in tanks, gines, indoor operations with motorized equipment troop compartments of armored vehicles, enclosed such as fork lifts, and indoor proof-testing or firing of communications vans, enclosed areas where portable, weapons (Figure 11-1).1 TYPICAL SOURCES OF EXPOSURE Natural sources of carbon monoxide include volca- tional health occurred during 1906, when the Medical nic eruptions, lightning strikes, and beds of growing Department of the University of Pennsylvania em- kelp. But atmospheric carbon monoxide primarily phasized the importance of carbon monoxide expo- results from the incomplete combustion of carbon- sures in the felt hat industry.8 aceous materials. In nonindustrial, urban environ- Early 20th-century scientific and medical literature ments, the major man-made source of carbon monox- documents not only the magnitude of the interest, ide is the incomplete combustion of motor-vehicle frequency, and types of poisoning potentials, but also fuels, with exhaust gases from internal combustion the medical importance of carbon monoxide poison- engines accounting for approximately 60% of emis- ings that occurred in both domestic and industrial sions.4 Because fuels manufactured during the early environments.2 Before equipment to quantify carbon 20th century (eg, water gas, coal gas, and producer monoxide was readily available, it was considered to gas) usually contained high concentrations of carbon be a prudent safety measure to regard all flames from monoxide, they caused innumerable instances of poi- carbonaceous sources that impinged against metal as soning. In contrast, natural gas—obtained from wells potential carbon monoxide exposure hazards: the in coal-bearing areas—contained only trace amounts metal would cool the fire and the resultant incomplete of carbon monoxide prior to incomplete combustion.1,2 combustion would produce carbon monoxide.2 Sev- Because carbon monoxide is a combustion by-prod- eral excellent historical reviews of carbon monoxide uct, toxic exposures are especially likely in conflagra- exposure, such as J. S. Haldane’s, which was based on tions of buildings, kilns, and grates; explosions or fires his 1915 Silliman Lectures at Yale University, contrib- in mines; the detonation of explosives; and even to- uted to the developing database.2,7,9 bacco smoke.1,5 Fires associated with timbering in mines, reinforcement of deep dugouts, and interiors Steel Manufacturing of burning buildings are recognized as sources of significant exposures to carbon monoxide.6 During Blast-furnace gas was a product of the steel indus- the early years of the 20th century, toxic exposures to try. The gas was produced during the smelting of iron people who attempted to remain warm using open ore, as a result of partial combustion when coke and coke braziers were not uncommon, especially among limestone mixes were injected into the blast furnace. occupants of dugouts or other small, ill-ventilated In a collection process from the upper stack, particu- structures. The most common cause of death in fires late and gaseous contaminants were removed using is smoke inhalation and therefore carbon monoxide is filtration and water scrubbing. The resultant blast- a major cause of death in individuals who succumb to furnace gas was carried by overhead pipes to be smoke inhalation.4 reintroduced into the furnace as a combustible source Effects of toxic gas exposures associated with the of heat for blast stoves, steam production, and gas- workplace were described by Tanguerel des Planches engine power. Although the composition of blast- in 1839 and Dr. Hermann Eulenberg in 1865. Claude furnace gas was variable, major components were, on Bernard first discovered the complex identified as average, nitrogen (57%), carbon monoxide (26%), car- carboxyhemoglobin in 1858.7 In the 1880s, Professor bon dioxide (11%), and hydrogen (3%–4%).2,10 Be- K. B. Lehmann and his students expanded the scien- cause the steel industry in the United States, with its tific database related to toxic gas exposures based on numerous facilities and industrial employees, was a animal experimentation, industrial observations, and prime source of carbon monoxide poisoning, the in- human control experiments. One of the first instances dustry provided the impetus for developing effective of the involvement of academic medicine in occupa- engineering and administrative controls. 399 Occupational Health: The Soldier and the Industrial Base Combustion Engine Exhaust lism of the methylene chloride to carbon monoxide.12 Methylene chloride is a readily volatile chemical that Shortly after gasoline engines were introduced as a is widely used in industry as a paint stripper, aerosol source of motive power, operators of gasoline launches propellant, and degreaser. As a consequence of the and drivers in taxicab garages frequently experienced volatility and lipid solubility, with uncontrolled use of signs and symptoms of carbon monoxide exposure.2 methylene chloride, exposure potentials are high and Production of carbon monoxide was demonstrated to the material is readily absorbed. Ineffective industrial be greater before the engine had warmed to normal ventilation of operations such as degreaser tanks or operating temperatures. Other conditions that gener- improper use of personal protective equipment may ated increased amounts of the gas included engines cause carboxyhemoglobin levels to rise.2 that were poorly tuned or operated at idling speed without a load.