Respiratory cancer among chloromethyl ether workers.

This report updates a historical cohort study of production workers employed at a chemical plant between first use of chloromethyl ethers (January 1948) and August 1971 when a series of improvements culminated in a closed system. Short-term employees previously excluded from the cohort have been added, and follow-up has been extended an additional 9 years. The 737 exposed and 2,120 unexposed workers were followed from entry to the end of 1981. Mortality from cancer of the respiratory tract was significantly greater among exposed workers than predicted by local rates [32 observed (Obs); 11.5 expected (Exp); Obs/Exp = 2.79; P less than .01]. When respiratory cancer was examined according to a cumulative index of exposure, there was a clear dose response evident, with risk increased more than tenfold at the highest doses but not increased at the lowest exposure levels. Although some exposures have apparently resulted in a short period from first exposure to development of respiratory cancer, a latent period of 10-19 years appears to be the most common response to exposure. This was true for all doses combined and for each dose category. The majority of employees at risk have passed through the Obs critical latent period for development of chloromethyl ether-related lung cancer. Although the numbers of cases Obs during recent years are still higher than Exp, risk has been declining toward Exp levels.