Exposures recorded for participants in the UK Chemical Warfare Agent Human Research Programme, 1941-1989.

OBJECTIVES This study describes exposures to military veterans who participated between 1941 and 1989 in British research at Porton Down on the effects of exposure to chemical warfare agents and to defences against those agents. The study is part of a programme of epidemiological research initiated in response to service veterans' concerns about possible long-term health effects of their participation. METHODS All entries in 97 books held in the Porton Down historical experimental archive covering the years 1939-1989 were reviewed. For tests between April 1941 and December 1989, data were abstracted on chemicals used, with additional detail abstracted for tests involving vesicants and nerve agents. For tests recorded during 1939-1941, similar data were abstracted for a representative sample of tests. RESULTS Historical data were abstracted for 17 303 veterans included in the cohort study of 18,276 servicemen who took part in tests at Porton Down between 1941 and 1989. The median number of days per veteran on which tests were carried out was 2 days. The median difference between the last and first day of testing was 4 days. A large number of chemicals were tested over this period (n = 492). The type of chemical tested varied over time. Exposures were often modified by respirator use or use of protective clothing or protective equipment. It was possible to assign a quantitative measure of cumulative exposure to 73% of veterans exposed to the vesicant sulphur mustard--3491 (34%) of exposed veterans had cumulative exposures > or =10.63 mg and for 70% of veterans exposed to the nerve agent sarin--658 (29%) of exposed veterans had cumulative exposures > or =15.0 mg min m(-3). Ninety-three per cent of veterans exposed to sulphur mustard were classified to a semi-quantitative scale of dermal effect--3771 (37%) had a vesicle or necrosed area, and 69% of veterans exposed to sarin could be categorized by change in blood cholinesterase activity--1033 (31%) had a depression in cholinesterase activity of > or =30%. CONCLUSIONS The experimental archive at Porton Down has proved to be a rich source of data on tests conducted between 1941 and 1989. It has been possible to categorize most veterans according to date of test, chemical group, chemical, type of protection and, for certain chemicals, level of exposure and/or degree of acute toxicity. These categorizations have been used to assign veterans to exposure groups for epidemiological analysis.