INTRODUCTION

Sulfur Mustard

Sulfur mustard (C₄H₈Cl₂S) is one of a class of chemical warfare agen ts known as vesicants because of their ability to form vesicles, or blisters, on exposed skin (see Figure 3-1). During WWI, exposed troops described the odor of this agent as a stench like mustard or garlic, hence its common name. Table 3-1 summarizes some characteristics of mustard agents and Lewisite. First noted for its toxic properties by dye chemists in the late 1880s, sulfur mustard has been referred to by a number of synonyms: S-mustard, to distinguish it from nitrogen mustard; ''Lost" or "S-Lost," from the names of two chemists who suggested it be used as a war gas (Lommel and Steinkopf); "yellow cross," for the identifying mark on WWI shells containing sulfur mustard; or Yperite, after the site of its first use in 1917. Although commonly and inaccurately referred to as mustard gas, the agent is a liquid at room temperature.

FIGURE 3-1

Vesicle formation on an Iranian patient, 16 hours after battlefield exposure to sulfur mustard. Reprinted from Willems, 1989, with permission from Annales Medicinae militaris Belgicae.

TABLE 3-1

Chemical and Physical Data.

Sulfur mustard produces skin blisters and damage to the eyes and respiratory tract, and it can be lethal at sufficiently high doses. It is a cellular poison and mutagen and a recognized human carcinogen. Battlefield use of sulfur mustard decreases the opponent's ability to fight by producing chemical burns on tissues that come into contact with either vapors or liquid droplets and aerosols. Exposed skin surfaces, eyes, and the linings of both the respiratory and the gastrointestinal tracts are all at risk, and the risks increase dramatically under hot, humid conditions.

From a military standpoint, one of sulfur mustard's most useful properties is its persistence. Droplets of this agent released in an explosion can deposit on numerous surfaces, evaporating slowly and posing a risk from inhalation as well as contact with the skin. Indeed, this very set of conditions was observed in WWI after mustard shelling (Haber, 1986). One reason for this persistence is the characteristic freezing temperature of sulfur mustard (13°C to 15°C). Droplets or bulk quantities would thus be expected to remain where initially deposited during cool or winter weather, under forest canopies, or under overgrown vegetation. Under certain conditions, bulk quantities of mustard agent spilled or splashed onto the soil would not degrade for months.

The exact date of the first sulfur mustard synthesis is somewhat unclear, but the first report may have been by Despretz in 1822. An 1860 report by Neimann describes a delayed-effect vesicant oil as a reaction product of ethylene on a mixture of sulfur chlorides. At that time, this product was identified as a compound [(C₂H₄)₂S₂Cl₂] different from sulfur mustard; however, the observed severe skin blistering, latent period of several hours, and subsequent slow healing are all typical of skin exposure to sulfur mustard. At about the same time, Guthrie (1859, 1860) published investigations describing yet another variant compound (thought to be C₄H₄S₂Cl₂), also produced from sulfur chloride in reaction with ethylene. The odor was "pungent," resembling that of "oil of mustard." Guthrie noted destruction of the epidermis when the thin skin between the fingers and around the eyes was exposed to the ''vapour" of this compound. When the liquid was allowed to remain on the skin, blister formation was observed. Finally, in 1886, a process to produce significant quantities of pure sulfur mustard was described by Meyer using sodium sulfide, ethylene chlorohydrin, and hydrochloric gas (Jackson, 1936; Meyer, 1886; Prentiss, 1937; West, 1919). This process was the one eventually used by the German war factories to fill the shells fired at Ypres (Haber, 1986).

RESEARCH PROGRAMS OF WORLD WAR I AND THE POSTWAR PERIOD

As outlined above, prior to the actual use of sulfur mustard as a war gas in 1917, the substance was little more than an interesting compound produced, along with hundreds of other compounds, by the emerging science of industrial chemistry in the last half of the nineteenth century. Thus, tragically, the combat casualties of WWI became the first large group of experimental subjects in studies of the medical effects of sulfur mustard. Organized research into chemical warfare agents began in earnest in Britain and France after the German chlorine gas attack in 1915. In the United States, it was 1917 before a formally organized chemical warfare research program was established. The history of the program has been documented by various authors and summarized by Cochrane (1946) in a classified report released to the public in 1991. The program began with an offer from the Bureau of Mines to the National Research Council (NRC) to mobilize the bureau's unique and specialized laboratories toward the investigation of poison gases.¹ With the U.S. declaration of war against Germany in 1917, the NRC Committee on Noxious Gases was formed to administer the research programs concerning poison gases, including sulfur mustard and later Lewisite.

In the United States and Europe, much of the research was focused on methods of mass production of sulfur mustard, development of other vesicants and war gases, and development of better gas masks and other equipment to protect troops from chemical attack. The overall research program was divided into sections, each of which was responsible for specific types of research, ranging from gas production processes to treatment of gas casualties. As the program matured, the various organizational structures were modified. The details of these modifications are not presented here because they are largely irrelevant to consideration of the health effects of mustard agents and Lewisite. One modification, however, may have set the stage for how research into these substances' medical effects has been conducted and directed ever since.

In 1918, a presidential order moved the research program from essentially civilian control under NRC to military control under the War Department. This move gave birth to the Chemical Warfare Service (CWS), which, to the present day, is responsible for the majority of research concerning chemical and biological warfare agents. As time went on this administrative change altered the direction of almost all investigations into the toxicology of vesicants and other chemical agents. Mainstream biomedical science is "hypothesis driven": when interesting results are obtained by an investigator, either that investigator or other groups begin further research to better understand what has been discovered, even if the interesting results are not directly relevant to the original questions being asked. In addition, the results of most biomedical research are published in "open literature," critically reviewed by outside experts and available to all.

In contrast, most military research is "applications driven": priorities are determined on the basis of military needs (e.g., treatment of acute injuries, development of protective clothing), and results not directly relevant to the original questions are seldom pursued. Such research is commonly classified and is published only for other military groups. The tight controls and restrictions on military research can result in a "stunted" body of literature that presents major limitations to later assessments in areas that were never pursued—in this case, the long-term health effects caused by exposure to chemical agents in general, and mustard agents and Lewisite in particular.

Researchers in the medical aspects of chemical warfare began their work in 1917 with few of the guideposts that are normally available from previous studies. The only literature available on the medical effects of sulfur mustard and Lewisite was that produced by the English and French, who had only a small head start with their research programs. Nevertheless, perusal of the significant papers published after the war from these groups reveals that multiple lines of investigation were quickly initiated and pursued. Some of the work done by the medical research groups examined the mechanisms of absorption of mustard agents into human skin, the effects of various ointments and antidotes on the severity of blisters and skin damage, and the pathological changes in the respiratory tract following inhalation of sulfur mustard vapor. Cochrane's history lists 22 papers and books published by 1920, which stood as the distillation of all significant investigations completed in the United States during WWI (Cochrane, 1946).

With the end of the war, the research program came to an end and CWS decreased drastically in size. The many research and production locations were also completely consolidated at the Edgewood Arsenal in Maryland. After a short period of relative uncertainty about its continued existence, CWS became part of the U.S. Army by an amendment to the National Defense Act on July 1, 1920.

Two later books included comments on the long-term effects of warfare gases. In 1925, Vedder published Medical Aspects of Chemical Warfare, in which he discounted any significant long-term sequelae of gassing and introduced the concept that "neurasthenic" conditions (an archaic term describing lassitude, decreased energy, and impaired functioning that, in Vedder's work, seemed to be used as a synonym for "psychosomatic") were the underlying factors in most veterans' claims of disability. Colonel Harry L. Gilchrist, in contrast, published an extensive comparative study on WWI casualties in 1928 that included detailed clinical descriptions of men who had been gassed in combat and a carefully researched chapter on the probable residual health effects of various gases (Gilchrist, 1928a,b). Gilchrist's work was a major contribution to knowledge about vesicant toxicity. Based on clinical examination of human gas victims and some animal experiments, as well as later follow-up studies of WWI veterans, Gilchrist found that the long-term effects of sulfur mustard were mainly respiratory, including emphysema, chronic asthma, and chronic bronchitis. Chronic conjunctivitis and corneal opacities were also described later by Gilchrist and Philip B. Matz (1933a,b; also see Appendix B for excerpt from Gilchrist and Matz, 1933b).

The period from 1920 until 1936 also saw the establishment of a Medical Research Division within the CWS. This group continued toxicological studies of chemical warfare agents, including sulfur and nitrogen mustards and Lewisite; investigated the lethal and sublethal concentrations of the agents; and renewed investigations into protective ointments. In addition, the group formalized what was known regarding treatment of gas casualties and attempted to examine the residual effects of exposure to various chemical warfare agents. Its work involved both animal and human experimentation. The experiments with human subjects, however, used only a few subjects mostly drawn from personnel, including the scientists themselves, working at Edgewood Arsenal.

For mustard agents and Lewisite, no major breakthroughs were made by the research efforts between 1920 and 1936. According to Cochrane, the lack of progress was traceable to a variety of factors. One of these factors was funding, often in short supply in a peacetime environment. Also, to appease public concern about poison gas production, significant efforts were spent trying to find peacetime uses for these agents. Another factor was the constant struggles and competition between different branches of the military, different departments within the CWS, and different scientific disciplines. Cochrane reports that the medical researchers, in direct competition with apparently more productive chemists, were especially vulnerable to funding shifts.

Thus, by the dawn of WWII, what was known about mustard agents and Lewisite (or many other agents, for that matter) was not organized into a cohesive body of literature. The clinical picture of the acute effects of exposure and some of the mechanisms of toxicity were well known (Gilchrist, 1928a,b; Vedder, 1925). There were clear guidelines for treatment of casualties, but the treatments were solely palliative. No effective ointments had been developed and nothing was available to prevent skin and lung damage. Even less was known about the long-term effects. So unorganized was the scientific base concerning vesicants that, when the 1941 version of the training manual for treatment of gas casualties (TM 8-285) was prepared for use in treating expected casualties in WWII, it did not include the carefully documented long-term effects of exposure reported by Gilchrist in 1928 and by Gilchrist and Matz in 1933.

This omission, not explained in Cochrane's history or elsewhere, was surprising to this committee. It is improbable that CWS did not know of Gilchrist's work, because it had been published in "open, nonclassified" literature, including one journal. In retrospect, we know that such an omission may well have unfavorably influenced the treatment and long-term follow-up of gassed soldiers in WWII, had such casualties occurred. In terms of the WWII testing programs with human subjects, this omission—coupled with an apparent disregard for the long-term effects of gas exposure—may have contributed to the absence of follow-up of these human subjects, despite the fact that the end points of many of the experiments were skin injury and burns (also see Chapter 4).

TESTING PROGRAMS AND CHEMICAL WARFARE PRODUCTION IN WORLD WAR II

As the war in Europe eroded U.S. neutrality, preparations began to revitalize and expand the activities of the Chemical Warfare Service. In order to obtain a greater base of scientific expertise, the War Department again came to the National Research Council for help (see Appendix C). In 1941, the research effort was reorganized and subsumed under a newly established Office of Scientific Research and Development (OSRD), eventually comprised of two working branches, the Committee on Medical Research (CMR) and the National Defense Research Committee (NDRC), and an Advisory Council. NRC's Committee on the Treatment of Gas Casualties (CTGC), experts in the fields of medicine and biological sciences, began working closely with the CMR to aid the effort by administering and supervising government grants to researchers and universities for a wide range of research regarding chemical warfare agents (see Figure 3-2 for OSRD organizational chart).

FIGURE 3-2

Organization of World War II civilian scientific research and testing programs. Chamber and field tests were conducted by the Chemical Warfare Service and the Navy Department, Office of Research and Inventions. Civilian researchers from the NDRC and CMR (more...)

One of the first assignments given to the CTGC was to review the scientific literature on the physiological effects of sulfur mustard and Lewisite, and on the methods tested for protection against injury and treatment of gas burns. The focus of the literature review was on acute toxicity data, but included longer-term effects. The first reviews were distributed among the various NDRC and CMR groups in August 1943 (Smith, 1943). There is no evidence that these reviews resulted in any changes or modifications of the protocols for the treatment or follow-up of human subjects in the experimental programs. On the subject of long-term effects of exposure, only Vedder's work, and not Gilchrist's, is mentioned in this review.

The focus of the following section is on the experiments conducted in the United States using human subjects; consideration of the animal experiments is included in later chapters, which survey the scientific literature. Similar experiments were also conducted in Great Britain, Canada, Australia, and the Soviet Union, as well as in Germany and Japan. The details of these experiments and these countries' chemical weapons programs are not included here. However, numerous references that provide information regarding these programs were examined by the committee, are included in the bibliography, and are specifically cited in this report where appropriate. One of the richest sources for information on the gas chamber experiments was reports released from the Naval Research Laboratory (NRL). Other primary source information regarding gas chamber experiments in locations other than the NRL was obtained by the committee from Edgewood Arsenal in Aberdeen, Maryland.

CWS carried out three basic types of experiments with human subjects. According to Cochrane, these testing programs involved the use of approximately 60,000 human subjects. Patch, or drop, tests were the most common and were used to assess the efficacy of a multitude of protective or decontamination ointments, treatments for mustard agent and Lewisite burns, effects of multiple exposures on sensitivity, and the effects of physical exercise on the severity of chemical burns. In addition, drop application of liquid mustard agents was commonly used in basic training to raise single blisters to impress upon the trainees the toxicity of these agents and the need for immediate responses to any orders to don gas masks. Chamber tests of various types were conducted to test the effectiveness of protective clothing, all of which had been impregnated with chemicals to retard vapor penetration. Finally, field tests involved the contamination of large or small areas of land with sulfur mustard or Lewisite. Human subjects were used in field tests to test protective clothing, to monitor the effects of the agents on animals in the test sites, and to take measurements of agent concentrations in soil and water samples. Table 3-2 summarizes the known major locations of these tests and the types of experiments done in each location.

TABLE 3-2

Known Gas Testing Facilities and Test Types.

Many veterans who were subjects in the chamber tests have obtained detailed records of their exposures from the Naval Research Laboratory. These reports often employ an outdated scientific notation. Table 3-3 summarizes the various notations used in NRL reports, along with other sources, to express concentrations, and compares these with modern notation. In addition, this table illustrates the difference between atmospheric concentration and the concept of cumulative exposure, in which both concentration and time of exposure are noted. For purposes of this report, the more modern notation is used and cumulative exposures are expressed in Ct (equivalent to mg min/m³) to avoid repetition, because the vast majority of chamber tests were conducted in 60-minute trials. To place the concentrations that follow into additional context, Table 3-4 summarizes the concentrations required to produce specific physiological effects.

TABLE 3-3

Concentration Versus Cumulative Exposure Level: Explanation of Notations in NRL Reports and Modern Literature.

TABLE 3-4

Summary of Major Biological End Points Characterizing Sulfur Mustard Exposure to Humans (at 16°C-27°C unless otherwise noted).

For further comparison, it may be useful to consider two additional calculations. First, according to the International Agency for Research on Cancer (IARC, 1975), the average and maximum atmospheric concentrations of sulfur mustard in combat zones were estimated to be approximately 20 and 33 mg/m³. To determine exposure levels, however, one must consider the duration of exposure to a given atmospheric concentration. The exposure threshold for death from respiratory damage has been estimated to be between 1,000 and 1,500 mg·min/m³ (Ct, see Table 3-4). Thus, fatal exposures on the battlefield in WWI must have lasted between 50 and 75 minutes (the product of 50 minutes and 20 mg/m³ would equal a Ct of 1,000), if the estimated atmospheric concentrations were sustained, or longer if the concentrations dropped substantially.

Recent Centers for Disease Control (CDC) recommendations for safe levels of exposure to mustard agents and Lewisite provide a second useful frame of reference. Responding to the mandated destruction of all unitary lethal and chemical munitions, CDC published chemical agent control limits for atmospheric exposures to chemical munitions in the Federal Register in 1988. For general population exposures, the limits are 0.0001 and 0.003 mg/m³ for sulfur mustard and Lewisite, respectively. For workers directly involved in munitions removal and destruction, the limits (averaged over 8 hours) are 0.003 mg/m ³ for both agents (CDC, 1988).

It is important to remember, when considering these comparisons, that the battlefield and estimated safe occupational levels of sulfur mustard and Lewisite refer to atmospheric concentrations, rather than "dose" level. However, it is the concentration and cumulative exposure to an unprotected target tissue (e.g., the eye, skin, or breathing passages) that determines the dose received and thus the damage to tissues from these agents. The presence of protective clothing and/or a gas mask reduces considerably the amount of agent reaching such a target tissue. Sections of this chapter to follow contain estimates and analysis of the probable cumulative exposures achieved in the chamber and field tests, as well as occupational situations.

Chamber Tests

Because the chamber tests were largely designed for the technical development of protective clothing, these tests were conducted by CWS and NRL in communication with the NDRC, rather than the CMR and CTGC. Thus, the sources used for information on concentrations and protocols for chamber tests included the Summary Technical Report of the NDRC and NRL technical reports. However, these sources are not exhaustive, and the details of chamber tests in locations such as Edgewood Arsenal and Great Lakes Naval Training Center were not made available to the committee for evaluation. Further, only the NRL has maintained accurate records of the individuals who participated in the tests (close to 2,500 men). Lacking similar information from the other locations, the total number of individuals involved in chamber tests is unknown. The vast majority of those participating in chamber tests were Caucasian men. A small number of African American and Japanese American soldiers were recruited for tests to determine possible differential skin effects of sulfur mustard on members of these races.

Similar to patch tests, there were a variety of types of chamber tests. For some chamber tests, the major questions were how long, under what conditions of temperature, and under what concentrations of gas would chloramide- or activated carbon-impregnated clothing afford protection of personnel against chemical attack with vesicants. The vesicant used most often was sulfur mustard, but nitrogen mustard and, probably, Lewisite were also used. These tests were called "man-break" tests. The common procedure was to equip men with gas masks² and clothe them in the impregnated suits (see Figure 3-3). The men would then enter the gas chamber (Figure 3-4) and remain there for periods from 60 minutes to 4 hours. The interiors of the chambers were most often maintained at 90°F and 65 percent relative humidity, because investigators were specifically interested in the durability of protective clothing under tropical conditions. Following the period in the chamber, the men wore their gas masks for an additional 5 minutes and remained in the suits for additional periods of time, ranging from 4 to 24 hours³ (Taylor et al., 1943; see Appendix D for excerpts and the Military Reports section, U.S. Navy, of the Bibliography for a complete listing of NRL reports examined). Twenty-four hours after each chamber trial, the men were examined for reddening of the skin (erythema), evidence that the vapor had penetrated the suits and burned the skin. The men were required to repeat the procedure and enter the chambers either every day or every other day until they developed moderate to intense erythema. The number of trials tolerated depended largely on the vesicant concentration in the chambers. For example, a technical report by Taylor and his colleagues documents a specific set of 60-minute trials in which, at a cumulative sulfur mustard exposure level of 600 Ct per trial, the average number of trials tolerated was 5.3, representing a low of 4 trials and a high of 14 trials (Taylor et al., 1945). In trials with cumulative exposures of 9,600 Ct per trial, the average number of trials tolerated was estimated at two, because all the men developed some erythema after the first trial.

FIGURE 3-3

U.S. Naval personnel dressed for World War II sulfur mustard experiments. Gas masks shown are Navy diaphragmtype masks. SOURCE: Heinen et al., 1945. Photograph provided by Naval Research Laboratory.

FIGURE 3-4

(A) Naval Research Laboratory (NRL) gas chamber. Interior dimensions of this chamber were 10 ft. by 15 ft., with a 12 ft. high ceiling. The chamber was designed to fit ten men and allow room for moderate exercise. (B) Photograph of the inside of a similar (more...)

The anatomical locations and intensity of erythema are reported in Taylor's paper for each individual. The majority of men experienced intense erythema that was widespread over their bodies, especially in moist areas of skin folds, such as behind the knee and under the arms, in large areas of the chest and shoulders, and on their arms and legs. Little involvement of areas such as the scrotum and buttocks was reported for this particular set of trials, possibly because the men wore an extra layer of impregnated undergarments.

In another set of trials reported by Heinen and his colleagues (1945), multiple cumulative exposure levels ranged from 50 to 700 Ct. In these experiments, the subjects were engaged in different levels of physical activity before, during, and after the chamber trials. No data, however, are included regarding the tests in which activity was performed inside the chambers. Significantly, subjects in this set of trials were not completely dressed in protective clothing. Most were dressed in standard issue attire but wore carbon-impregnated suspenders. It was thought that the suspenders would protect a strip of skin that could then be compared with skin areas that were unprotected. In addition, only a few men were given impregnated underwear. Results from this set of trials are documented with photographs that show burns to the genital areas of many of the men. In one series, of 24 men participating, 13 experienced crusted lesions to the scrotum that were characterized as severe, and 8 experienced severe lesions to the penis. These lesions took up to one month to heal, according to the report.

In general, these two reports are representative of many of the chamber tests conducted at NRL (Washington, D.C.), Edgewood Arsenal (Maryland), Great Lakes Naval Training Center (Illinois), and, for a short time, at Camp Sibert, Alabama. The concentrations, times of exposures, and types of chemical agents used in other locations may not be similar, however, and full reports of other chamber tests were not made available to this committee. There is evidence that some chamber tests may have been done with higher cumulative exposures, because Taylor and colleagues (1945) refer to ranges of 3,000 to 11,000 Ct of sulfur mustard used at Edgewood Arsenal.

Chamber tests were also conducted in Panama, North Carolina, and Maryland. These tests were called "wear tests," designed to see how the impregnated clothing stood up to use under possible combat conditions. Thus, the men wore the protective suits during drills and combat simulations, ranging from 1 day of amphibious training to 6 weeks of simulated combat. Following this, the men entered gas chambers in these suits, for 60-minute trials (as in the man-break tests), until erythema developed. The data reported in the Summary Technical Report of the NRDC (OSRD, 1946) show a range of 1.0 to 2.2 hours chamber time before erythema developed in this group of subjects. These data are difficult to compare with other chamber tests, however, because only micrograms of sulfur mustard were reported without the usual accompanying notation regarding volume. If one assumes that the micrograms listed were per liter, then the exposures ranged from 300 to 2,400 Ct in this series of chamber trials. Finally, some men participated in arm chamber tests of protective ointments or clothing materials. In these, the arms of the men were placed in a wind tunnel with cumulative exposures reported to be 1,200 Ct.

Some physiological measurements, including temperature and blood counts, were done on men participating in some of the tests, but these physiological measurements were not generally reported in the technical summaries. For those men who participated in Naval Research Laboratory tests, records of the experimental conditions, as well as any physiological measurements, were kept for each test subject and are available from NRL to individuals through the Freedom of Information Act (also see Chapter 4).

RESEARCH, USE, AND DISPOSAL OF CHEMICAL WEAPONS AFTER WORLD WAR II

CONCLUSIONS AND FURTHER ANALYSIS

The committee reached two principal conclusions based on its analysis of the chemical warfare testing programs from WWI through 1975. These conclusions relate directly to the estimated level of exposure to mustard agents and Lewisite experienced by the WWII chamber and field test subjects and to the exposures of workers in the Chemical Warfare Service during WWII. In addition, the committee's conclusions are pertinent to the health care concerns of those who have been injured by use of these agents in recent wars and conflicts, or who may be exposed in the future from belligerent use of these agents or through accidental exposure during their disposal.

1.

The lack of follow-up health assessments of the human subjects in WWII gas chamber tests and field tests severely diminished the amount and quality of information that could be applied in the assessment of long-term health consequences of exposure to mustard agents and Lewisite. Although the reasons underlying the lack of follow-up health assessments are not explicit from the numerous documents and materials considered by this committee, a number of factors may have played a role:

• There was no unified body of information, based on WWI research and the research done in the period from 1918 to 1939, when research was intensified in the early pre-WWII period. This lack of information seems to have contributed directly to a lack of appreciation for the serious long-term health risks associated with exposure to mustard agents and Lewisite, specifically chronic bronchitis, emphysema, chronic laryngitis, corneal opacities, chronic conjunctivitis, and keratitis.
• Scientific inquiry was controlled by the military establishment, whose primary concern was with acute rather than long-term injury. This control also probably contributed to the paucity of animal or other types of studies, following WWII, aimed toward elucidation of long-term consequences of damage to specific physiological systems. For example, no long-term follow-up was done on workers involved in chemical warfare materials production, despite the high level of injuries that occurred.
• The atmosphere of immediacy caused by the outbreak of war, and the resulting prioritization of expected combat injuries, at least strengthened the focus on acute damage from chemical warfare agents, and at worst dampened any sensitivities that were present regarding the future health of human subjects or chemical warfare production workers.
• Once the war was over, there may also have been ambiguities about which federal department or agency should have had responsibility for follow-up of veterans. Although the former Veterans Administration (VA) had that role traditionally, the VA could not have been expected to know about the testing programs and their possible effects on the health of human subjects without communication from the military.
• Finally, and related to the issue of responsibility for follow-up, the continued secrecy maintained by the military regarding the WWII testing programs also created a barrier to follow-up assessments of exposed individuals. Even during the present study, which follows a five-year period of intensifying public scrutiny of these WWII programs, obtaining certain types of information was not easy and often involved piecing together bits of data from numerous sources. In fact, this committee was commonly required by many DoD and Department of the Army offices to file all requests under the Freedom of Information Act. These requirements were often imposed even on the present Department of Veterans Affairs (VA), when it attempted to aid this committee by making certain requests for information regarding the possible existence of records of individuals who participated in the testing programs (see Appendix E). The most valuable primary source data were received from the Naval Research Laboratory and NRC's Office of Archives and Information Services. This committee is especially grateful to the NRL for its commitment to open its files. The NRL stands alone among sections of the Department of Defense in the maintenance of files and reports, and the sharing of those files with this committee and with the affected veterans.

2.

The levels of exposure to mustard agents or Lewisite experienced by the test human subjects may have been much higher than inferred in the summaries of the experiments and field tests. As in all chemical exposures, such exposure levels directly relate to the types and severities of exposure-induced injuries and diseases. One can infer the cumulative exposures to the skin of chamber subjects strictly on the basis that skin damage was the end point of these experiments (see Table 3-4). Therefore, if all other types of exposures were held to zero, these subjects received between 100 and 300 Ct. As has been documented, some of the subjects were hospitalized for as long as "a month or so" (Taylor et al., 1943). Thus, exposures to the skin may have been as high as 1,000-2,000 Ct. Under the hot, humid conditions in the chambers, however, lower exposure levels would have resulted in similar injuries (Papirmeister et al., 1991). The dose to the skin from such exposures would have been as high as those observed under battlefield and occupational conditions. Further, some sulfur mustard would also have been absorbed from the skin into the systemic circulation.

In the chamber experiments, unmasked subjects were required to remain in their protective clothing from 4 to 24 hours following chamber trials, allowing ample opportunity for additional contact and inhalation exposures from contaminated surfaces and clothing. Another factor that probably resulted in some inhalation exposure of subjects in the chamber tests was vomiting during the period subjects were in the chamber. This was reported by at least one of the subjects who spoke at the public hearing; this person reported conjunctivitis and laryngitis following such a vomiting incident on his seventh day of testing (Elmer Hood, public hearing statement; see also Appendix G). Vomiting presumably would result in removal of the mask while in the chamber, with a resulting inhalation exposure of unknown duration at the chamber concentration being tested.

The most important route of additional exposure in the chamber and field tests was probably gas mask leakage. From the information available to the committee, it appears that the vast majority of the human subjects in the chamber and field tests wore full-face gas masks during their exposures. In fact, the documented exposures at the Naval Research Laboratory were delivered at concentrations and for durations that would have caused lethal respiratory effects if the subjects had not been equipped with respiratory protection. Thus, exposure of the respiratory tract and eye to the agent would have depended on the protection factor (PF) afforded by the gas masks. The PF of a full-face respirator (e.g., a gas mask) is calculated as the ratio of the ambient concentration of the contaminant to the concentration inside the mask, which in turn depends on both leakage around the respirator and contaminant penetration of the gas mask canister. A PF of 100 equals a penetration of 1 percent of the contaminant into the mask (Adley and Uhle, 1969). A PF of 50 to 100, based primarily on leakage around facemasks, has been reported for relatively modern (post-WWII) full-face respirators (Hyatt, 1976). Estimates from industrial hygiene research, however, indicate that the level of protection achieved in actual use of a respirator is usually below the stated PF for that respirator (National Institute of Occupational Safety and Health, 1974). Thus, modern respirators are likely to function closer to the lower PF estimate of 50. In practical terms, even if the respirator actually achieved a PF of 100, subjects exposed to a concentration of 100 mg/m³ of sulfur mustard would be breathing a concentration as high as 1 mg/m³ inside the mask, corresponding to a cumulative exposure of 60 Ct over a single 60-minute trial. At even lower concentrations—under the odor threshold (0.6 mg/m³)—the subjects may well have been unaware of any leakage through their masks (see Box 3-1). Information on the breakthrough capacity of the gas mask cartridges used in the WWII chamber tests was not available to the committee, but it is known that prolonged use of cartridges can result in breakthrough of the agent by exceeding the capacity of the absorbent filter material (Stampfer, 1982).

BOX 3-1

ODOR THRESHOLD FOR SULFUR MUSTARD AND LEWISITE: COMPARISON WITH TISSUE DAMAGE THRESHOLDS. Even when enough agent had broken through their gas mask canisters to produce symptoms, chamber test subjects may not have noticed it, at least by odor. The odor (more...)

In the NRL chamber test reports examined by the present committee, when gas mask types were listed, the masks used were Mark III or Mark IV Navy diaphragm gas masks. These masks were probably equipped with M9A1 (prior to July 1943) or M9A2 canisters that contained Whetlerite, a copper-, chromium-, and silver-impregnated activated charcoal as the sorbent (Brophy et al., 1959). The PF afforded by these masks for sulfur mustard or Lewisite was not available to the committee. However, an individual involved in this testing reported that the WWII British and U.S. masks were very effective in removing sulfur mustard (Howard Skipper, personal communication; see Appendix A). Yet some chamber tests were conducted at high concentrations. For example, a test conducted at chamber concentration of 100 mg/m³ for 60 minutes would have resulted in a cumulative, unprotected, exposure of 30,000 Ct over five trials. Even an assumed PF of 1,000 for the gas mask (10 times greater than that estimated for modern full-face respirators) would have resulted in concentrations as high as 0.1 mg/m³ in each trial, corresponding to a cumulative exposure of 6 Ct just from the inspired air in each trial. This would have been below the odor threshold for sulfur mustard and, over five trials, would have resulted in a cumulative inhalation exposure of 30 Ct, enough to cause signs and symptoms in the eyes and respiratory tract (see Table 3-4). If a more realistic estimate is used, such as a mask with a PF of 100, the per trial exposure would have been 60 Ct. Over five trials then, a subject could have had an inhalation exposure of 300 Ct, more than sufficient to cause an incapacitating injury (see Table 3-4). It is important to remember that any such inhalation exposure would have been in addition to any skin exposure through breakdown of the protective clothing.

It is important to note also that the gas masks and clothing used in the NRL tests were worn repeatedly by the subjects. In at least one series of studies, it was reported that the rubber of the gas mask facepieces and connecting tubes absorbed enough sulfur mustard after 12 to 15 exposures to cause conjunctivitis, laryngitis, and erythema of the face (Taylor et al., 1943). Therefore it is clear that some exposure to the respiratory tract occurred from absorption of sulfur mustard on masks. Finally, as mentioned previously, the special diaphragm element in the types of gas masks used in the NRL chamber tests was eventually shown to provide an additional route of mask leakage, independent of the filter capacity (Brophy et al., 1959).

The presence of erythema of the face, conjunctivitis, laryngitis, or bronchitis within 24 to 72 hours following an exposure to sulfur mustard or Lewisite would be clear evidence that a significant inhalation and eye exposure had occurred, even if the subject was wearing a mask during the exposure. Conversely, it would appear that a lack of such symptoms following even a low-level exposure of 5 to 6 days to sulfur mustard would indicate a cumulative exposure (Ct) of less than about 12 Ct (see Table 3-4). However, in terms of the Centers for Disease Control's estimates of permissible exposure levels (CDC, 1988), the exposures actually reaching the breathing zone of chamber subjects (from the above example, 0.1 mg/m³ sulfur mustard breakthrough with a gas mask rated at 1,000 PF) may have been more than 1,000 times the general population agent control limits (0.0001 mg/m³ for sulfur mustard), and 33 times the control limits for occupational exposure (0.003 mg/m³ for sulfur mustard). In reality, some of the subjects in the chamber tests and field trials almost certainly breathed concentrations 10 or more times the 0.1 mg/m³ level for at least a part of their exposures.

The focus here on chamber and field test subjects is not meant to discount the probable exposure levels experienced by those who were involved in the production or handling of mustard agents and Lewisite. Indeed, as outlined above, the poor safety record of the Chemical Warfare Service during the peak years of production, the high rate of agent-induced injuries, and the anecdotal reports of perceptible odors of sulfur mustard in the manufacturing areas argue that workers and gas handlers were often exposed to levels of mustard agents and Lewisite sufficient to cause short- and long-term health effects. Thus, these individuals should also be considered at risk for any of the adverse health effects this report identifies.

In conclusion, the dose of sulfur mustard to the skin, eye, and respiratory tracts of the human subjects was substantial, especially in the case of the subjects involved in the chamber tests. Doses to the skin were probably equivalent to those received under combat conditions. Consideration of the probable gas mask leakage, additional exposures from contact or vapors from the clothing, accidents, and the documented signs and symptoms in the chamber test records indicate that the doses received by the human subjects were equivalent to those received in occupational exposures and, perhaps, even battlefield exposures.

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Footnotes

1

The National Research Council was in 1917 and is today part of the National Academy of Sciences. The NRC was directly involved in defense research programs during both World War I and World War II. A description of this involvement is included in Appendix C.

2

The gas masks used were Navy Mark III or Mark IV diaphragm-type masks, designed to facilitate speaking during mask use. These masks were eventually removed from use by the military, because the diaphragms were leaky (for a fuller discussion, see the Conclusions and Further Analysis section of this chapter).

3

It is not clear whether sulfur mustard, which is very persistent and evaporates slowly, was still present on the surface of the suits and, thus, a possible source of further contamination by inhalation or contact (fuller discussion is included at the end of this chapter).

4

Canisters equipped with asbestos filters included the M9A1 and the M10A2 canisters (Brophy et al., 1959). The model numbers of canisters used in gas masks employed in the chamber or field tests are not known, but M9A1 canisters were in common use prior to July 1943 (Brophy et al., 1959).

5

Review and analysis of the Beebe and Norman papers are included in Chapter 6.