Increased cardiovascular mortality and suicide after methyl chloride exposure.

ABSTRACT

OBJECTIVES: Methyl chloride leakage from a refrigerator occurred on board an Icelandic fishing vessel in 1963. Many of the crew members were hospitalized due to various neurological symptoms and signs. The aim was to study long-term mortality. METHODS: This is a cohort study. Five referents were selected from registries of deckhands and officers matched to each crew member according to age and occupation. Follow-up was through record linkage of personal identifiers with the nation-wide mortality registry. Hazard ratios (HR) and 95% confidence intervals (CI) were estimated in Cox proportional hazards model. RESULTS: The intoxicated crew was composed of 20 deckhands and 7 officers; the reference group counted 100 deckhands and 35 officers. Follow-up to the end of 2010; 14 of the exposed deckhands and 6 of the officers had died, versus 49 deckhands and 26 officers among the reference group. For all cardiovascular events, the HR was 2.06 (95% CI 1.02-4.15), for acute coronary heart disease, the HR was 3.12 (95% CI 1.11-8.78), for cerebrovascular diseases, the HR was 5.35 (1.18-24.35), and for suicide, the HR was 13.76 (1.18-160.07). CONCLUSIONS: Follow-up showed increased mortality due to cardiovascular diseases after 47 years. The suicide cases had developed severe depression after the methyl chloride intoxication that was related to the exposure. The use of the personal identifiers and the population registries strengthen the study. Detailed information on risk factors for chronic diseases is lacking in this study; however, the matching by occupation renders some similarity to the groups compared in the study.