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A cohort mortality study of employees exposed to chlorinated chemicals
Author(s) -
Wong Otto
Publication year - 1988
Publication title -
american journal of industrial medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.7
H-Index - 104
eISSN - 1097-0274
pISSN - 0271-3586
DOI - 10.1002/ajim.4700140406
Subject(s) - medicine , cohort , cohort study , standardized mortality ratio , excess mortality , lung cancer , epidemiology , confidence interval , cancer , hazard ratio , occupational cancer , demography , environmental health , mortality rate , sociology
The cohort of this historical prospective mortality study consisted of 697 male employees at a chlorination plant. A majority of the cohort was potentially exposed to benzotrichloride, benzylchloride, benzoyle chloride, and other related chemicals. The mortality experience of the cohort was observed from 1943 through 1982. For the cohort as a whole, no statistically significant mortality excess was detected. The overall Standardized Mortality Ratio (SMR) was 100, and the SMR for all cancers combined was 122 (not significant). The respiratory cancer SMR for the cohort as a whole was 246 (7 observed vs. 2.8 expected). The excess was of borderline statistical significance, the lower 95% confidence limit being 99. Analysis by race showed that all 7 resipiratory cancer deaths came from the white male employees, with an SMR of 265 (p<0.05). The respiratory cancer mortality excess was higher among employees in maintenance (SMR = 229) than among those in operations or production (SMR = 178). The lung cancer mortality excess among the laboratory employees was statistically significant (SMR = 1292). However, this observation should be viewed with caution, since it was based on only 2 deaths. Further analysis indicated that the respiratory cancer mortality excess was limited to the male employees with 15 or more years of employment (SMR = 379, p < 0.05). Based on animal data as well as other epidemiologic studies, together with the internal consistency of analysis by length of employment, the data suggest an association between the chlorination process of toluene at the plant and an increased risk of respiratory cancer. Limitations of the study, including the small sample size (especially for some subcohort analyses) and potential confounding factors (including cigarette smoking and other occupational exposures), are discussed.