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BACKGROUND: This study updates the mortality of a cohort of shoeworkers exposed to organic solvents. The original study examined the possibility of excess leukemia mortality since toluene, a homologue of benzene, was used in the manufacturing process. That study did not find an excess for leukemia but did find a statistically significant excess of lung cancer mortality. METHODS: Two shoe manufacturing plants, located in the state of Ohio, were selected for this study. Workers who accumulated one month or more employment at either plant during the years 1940-1979 were included in the analysis. Vital status follow-up was ascertained through December 31, 1999 using the National Death Index and other sources. 7,828 workers, contributing 300,777 person-years-at-risk, were available for analysis. 67.5% of this cohort were female, 32.5% were male. Through 1999, 40% of this cohort was deceased. Analysis conducted included calculating standardized mortality ratios for selected causes of death and tests for trend with duration of employment. RESULTS: The original finding of a statistically significant excess of lung cancer deaths in this cohort persisted with additional years of follow-up. This excess was found in both females and in males. A stratified analysis identified the highest mortality elevation among workers in Plant 2 who were employed less than two years. Trend tests did not indicate a statistically elevated positive trend between lung cancer risk and duration of employment. A significant excess of deaths due to mental disorders, in particular senile dementia, was a new finding in the updated analysis. This relationship has been detected in other studies of solvent-exposed workers. Death due to leukemia was not significantly elevated in the updated analysis. CONCLUSION: This study indicates that there may be an association between excess lung cancer mortality and exposure to chronic, low levels of organic solvents. Although the strength of this association is weakened by the lack of increasing lung cancer risk in relation to duration of employment, other studies have supported this association. Study limitations include the lack of detailed exposure records over time and the absence of individual smoking histories. |
