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Objective
To study whether there may be long-term effects on the mortality and cancer morbidity of participants in experimental research related to chemical warfare agents conducted at the UK research facility at Porton Down.
Design
Historical cohort study.
Setting and Participants
18 276 male members of the UK armed forces who spent one or more short periods at Porton Down between 1941 and 1989 and a comparison group of 17 600 non-Porton Down veterans followed to 31 December, 2004. All veterans were considered for the cancer analyses, excluding those known to have died or been lost to follow-up before 1 January 1971: 17 013 Porton Down and 16 520 non-Porton Down veterans.
Main Outcome Measures
Mortality and cancer rates in Porton Down veterans were compared to those of non-Porton Down veterans and the general population, adjusted for age and calendar period.
Results
Porton Down and non-Porton Down veterans were similar in military and demographic characteristics. Year of enlistment was the same (median = 1951) but the Porton Down veterans had longer military service (median = 6.2 vs 5.0 years). After a median follow-up of 43 years, 7306 and 6900 respectively had died. All-cause mortality was slightly greater in Porton Down veterans (RR 1.06, 95% CI 1.03 to 1.10, p<0.001), more so for deaths outside the UK (1.26, 1.09 to 1.46). Of 12 cause-specific groups examined, RRs were increased for deaths attributed to infectious and parasitic (1.57, 1.07 to 2.29), genitourinary (1.46, 1.04 to 2.04), circulatory (1.07, 1.01 to 1.12), and external (non-medical) (1.17, 1.00 to 1.37) causes and decreased for deaths attributed to in situ, benign and unspecified neoplasms (0.60, 0.37 to 0.99). There was no clear relation between chemical exposure group and cause-specific mortality. The mortality of each group was lower than that of the general population (SMR 0.88, 0.85 to 0.90; 0.82, 0.80 to 0.84 respectively). 3457 cancers were reported in Porton Down veterans and 3380 in non-Porton Down veterans. While overall cancer morbidity was the same (RR 1.00, 95% CI 0.95 to 1.05), Porton Down veterans had higher rates of ill-defined malignant neoplasms (1.12; 1.02 to 1.22), in situ neoplasms (1.45; 1.06 to 2.00) and those of uncertain or unknown behaviour (1.32; 1.01 to 1.73).
Conclusions
Mortality was slightly higher in Porton Down than non-Porton Down veterans. With the lack of information on other important factors, such as smoking or service overseas, it is not possible to attribute the small excess mortality to chemical exposures at Porton Down. Overall cancer morbidity in Porton Down veterans was no different from that in non-Porton Down veterans.