Long-term pulmonary complications in combatants exposed to mustard gas: a historical cohort study

Background Sulphur mustard (mustard gas), the most widely used chemical agent in the Iran–Iraq war, affects many organs including the skin, the gastrointestinal and respiratory tracts, and the central nervous system. The aim of this study was to assess the cumulative incidence rate and annual incidence rate of pulmonary complications, and the rate ratio of related factors. Methods In a retrospective cohort study of 1337 soldiers with a history of mustard gas exposure, factors such as age, smoking habit, number of exposure episodes, and the use of gas masks were determined, together with an assessment of their relationship to the occurrence of long-term pulmonary complications. All patients residing in the Tehran area were enrolled in the study. Data collection was based on the subjects' medical records and included clinical, spirometric, and in some cases histopathological findings. Results The cumulative incidence rate of pulmonary complications was 31.6%; the lowest annual incidence rate was noted during the first year of follow-up (0.75/1000), and the highest rate recorded in the seventh year (76.9/1000). Estimated relative risks (RR) for various age groups are as follows: 1.13 (95% CI: 0.88, 1.46) for those aged 21–25 years; 1.49 (95% CI: 1.10, 2.01) for ages 26–30; 1.70 (95% CI: 1.20, 2.40) for ages 31–35; and 2.09 (95% CI: 1.57, 2.77) for subjects aged ≥36. RR with regard to other factors were: more than one versus single exposure 0.69 (95% CI: 0.42, 1.12); smoking versus non-smoking 1.08 (95% CI: 0.80, 1.45), and unprotected exposure versus protective mask use 3.04 (95% CI: 2.20, 4.20). Conclusion The estimated risk of pulmonary complications from war exposure to mustard gas increased with age and for soldiers who had not worn masks.