There was, in fact, no long-term follow-up of any of the thousands of individuals exposed to these agents during WWII as evidenced by the accompanying lack of epidemiological studies of chemical warfare production workers, war gas handlers and trainers, and combat casualties of the Bari harbor bombing. The committee was particularly dismayed at this lack of epidemiological and follow-up data from the United States, despite the availability of a large cohort of civilian workers and military personnel who were involved in chemical warfare production and training, as well as the individuals who served as human subjects in chemical warfare testing programs. The committee was forced to rely on studies done in Japan and Great Britain to assess what was known about the long-term health risks from occupational exposure to mustard agents and Lewisite. As demonstrated in Chapters 3 and 7, such occupational data are directly relevant to the assessment of the potential effects of mustard agent and Lewisite exposure in the experimental testing programs, because the levels of exposure to mustard agents or Lewisite experienced by the human subjects may have been much higher than inferred in the summaries of the gas chamber and field tests.

These exposures were likely as high as those estimated for battlefield and occupational exposures, due to cumulative skin exposure compounded by inhalation exposure. Numerous lines of evidence demonstrate that inhalation exposures did indeed occur (see Chapter 3 and 7). First, modern gas masks have efficiency ratings (or PF) between 50 and 100 (a PF of 100 means that 1 percent of the contaminant in the atmosphere will penetrate a mask's filter canister); however, the efficiency achieved in actual use has been demonstrated to be much lower. Even if a much higher PF of 1,000 is assumed for the gas masks used in the WWII testing programs, penetration of sufficient amounts of the agents to cause respiratory and ocular signs and symptoms would have been expected at many of the concentrations used in the experiments. Second, there is documentation in the actual records of these experiments, as well as official histories of production settings, that respiratory and ocular symptoms and injuries did occur, and that problems were encountered with gas masks leaking after repeated use. Third, the specific diaphragm type of gas mask used in the gas chamber tests was eventually shown to be leaky due to penetration of the diaphragm  element, independent of the filter canister employed.

The reasons for the lack of follow-up of human subjects and combat casualties, as well as gas production, handling, and training personnel, can only be surmised, but the climate of secrecy within which the WWII chemical warfare production and testing programs were conducted is probably a key factor.