Acute response to Sarin in veterans tested at Porton Down

1. Acute response to Sarin in veterans tested at Porton Down Thomas Keegan1, Claire Brooks2, Toby Langdon2, Sue Walker3, Lucy Carpenter2, Katherine Venables3 1Lancaster University LA1 4YD 2Department of Public Health, University of Oxford, Oxford OX3 7LF 3Dstl Porton Down, Salisbury, SP4 0JQ Table 1 (below) Number of human nerve agent tests at Porton Down, by nerve agent type and decade. BackgroundPorton Down is the UK’s centre for research into chemical defence. Up to 30,000 servicemen have been involved in tests at Porton Down since WWI. Mortality and cancer incidence has been examined in over 18,000 Porton Down veterans who took part in tests between 1941 and 1989 (BMJ 2009). Here we draw on data from that cohort to describe exposures to the nerve agent sarin and measures of associated acute biological effect. Methods Data on chemical and non-chemical exposures were manually abstracted from the Porton Down historical archive. For every test, the name of the chemical(s) and date of test were abstracted. For nerve agents and vesicants, additional data were abstracted: exposure intensity, duration, route, presence of exposure modifiers. Maximum change in cholinesterase (ChE) was calculated. Data on pupil size change was also abstracted. Table 2 (below) Number sarin tests by exposure route and nerve agent type. Porton Down 1945-1989. Results Nerve agent tests took place between 1945 and 1987, when 3597 veterans were involved in 4299 tests. The most commonly tested nerve agent was sarin (2980 veterans; 3511 tests). Most sarin tests were by inhalation (85%) with 8% dermal and 3% ocular. Over half of sarin tests (53%) were unprotected. Data on change in ChE were available for 712 inhalation and 273 dermal tests. For unprotected inhalation, median percentage RBC ChE activity decreased with increasing sarin exposure (Ct = concentration x time): for sarin Ct <5 mg.min/m3, median ∆ RBC ChE was -25%; for Ct >10 mg.min/m3, median ∆ RBC ChE was -56%). For tests with chemical protection median RBC ChE activity also decreased with increasing sarin exposure. Change in pupil size was available for 744 sarin tests. Conclusions Sarin was the nerve agent most frequently tested on veterans at Porton Down. Availability of data on exposure intensity and acute effect has allowed quantitative assessment of the effect on exposure of physical and chemical modifiers. Table 2 (below) Percentage change in red blood cell cholinesterase activity after inhalation exposure to sarin, by protection status. Table shows tests for which data on both Ct and change in ChE were available. Acknowledgements Funding: Medical Research Council (G0200288, funds from the UK Ministry of Defence. We thank the Ministry of Defence Veterans Policy Unit; Defence Science and Technology Laboratory, Porton Down; Porton Down Veterans Support Group ISEE conference Dublin 2009