Sarin exposures in a cohort of British military participants in human experimental research at Porton Down 1945-1987

Background The effects of exposure to chemical warfare agents in humans are topical. Porton Down is the UK’s centre for research on chemical warfare where, since WWI, a programme of experiments involving ~30 000 participants drawn from the UK armed services has been undertaken. Objectives Our aim is to report on exposures to nerve agents, particularly sarin, using detailed exposure data not explored in a previous analysis. Methods In this paper, we have used existing data on exposures to servicemen who attended the human volunteer programme at Porton Down to examine exposures to nerve agents in general and to sarin in particular. Results Six principal nerve agents were tested on humans between 1945 and 1987. Of all 4299 nerve agent tests recorded, 3511 (82%) were with sarin, most commonly in an exposure chamber, with inhalation being the commonest exposure route (85%). Biological response to sarin exposure was expressed as percentage change in cholinesterase activity and, less commonly, change in pupil size. For red blood cell cholinesterase, median inhibition for inhalation tests was 41% (interquartile range 28–51%), with a maximum of 87%. For dermal exposures the maximum inhibition recorded was 99%. There was a clear association between increasing exposure to sarin and depression of cholinesterase activity but the strength and direction of the association varied by exposure route and the presence of chemical or physical protection. Pupil size decreased with increased exposure but this relationship was less clear when modifiers, such as atropine drops, were present. Conclusions These results, drawn from high quality experimental data, offer a unique insight into the effects of these chemical agents on humans.