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 ~30000 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.

Prevalence of blindness and cataract surgical outcomes in Takeo Province, Cambodia.

PURPOSE: To estimate the prevalence of blindness and cataract surgical outcomes in persons 50 years or older above in Takeo Province, Cambodia. DESIGN: A population based survey. METHODS: A total of 93 villages were selected through probability proportionate to size using the Rapid Assessment of Avoidable Blindness methodology. Households from 93 villages were selected using compact segment sampling. Visual acuity (VA) of 4650 people 50 years or older was tested and lens status and cause of visual impairment were assessed. RESULTS: The response rate was 96.2%. The age- and sex-adjusted prevalence of bilateral blindness [presenting visual acuity (PVA) <3/60 in the better eye] was 3.4% (95% confidence interval, 2.8%-4.0%), resulting in an estimated 4187 people blind in Takeo Province. The age- and sex-adjusted prevalence of low vision (PVA <6/18 to 3/60) was 21.1%, an estimated 25,900 people. Cataract surgical coverage in the bilaterally blind was 64.7% (female 59.5%, male 78.1%). Cataract surgical outcome was poor (best-corrected visual acuity <6/60) in only 7.7% and good in 88.7% (best-corrected visual acuity ≥6/18) of eyes operated in the last 5 years before the survey. CONCLUSIONS: The cataract surgical coverage for women is less than that for men. The increased life expectancy in Cambodia and the fact that women constitute 60.6% of the population (aged ≥50 years) at Takeo Province could have had an impact on cataract workload and high prevalence of blindness. A repeated survey using the same methodology after 8-12 years might be helpful in proving genuine change over time.