Mortality from lung cancer among workers employed in formaldehyde industries

Abstract

A historical cohort of 26,561 workers employed in ten facilities was assembled to evaluate cancer risks associated with exposure to formaldehyde. Historical exposures to formaldehyde by job, work area, plant, and calendar time were estimated using monitoring data available from participating plants, comments from long-term workers and company officials, exposure evaluations from walk-through surveys conducted by project industrial hygienists, and results from monitoring specifically performed for this project. A previous report of findings from this study noted a 30% excess mortality from lung cancer among wage workers. The relative risk for lung cancer (whether estimated by SMRs or SRRs) 20 or more years after first exposure did not generally rise with increasing exposure to formaldehyde. Various estimates of exposure were investigated including duration, intensity, peak, cumulative, and average, and by exposures lagged by 5, 10, 20, and 30 years. The excess did not appear to arise gradually, but emerged suddenly among workers whose total cumulative exposure was less than 0.1 ppm-years. Slightly positive, but nonsignificant, exposure-response associations between lung cancer and level of formaldehyde occurred in only a few out of a large number of comparisons (e.g., for persons hired before the start dates for the study and for workers also exposed to particulates). There was a lack of consistency among the various plants for risk of lung cancer, with six plants having elevated SMRs and four plants having deficits. Mortality from lung cancer was more strongly associated with exposure to other substances including phenol, melamine, urea, and wood dust than with exposure to formaldehyde. Workers exposed to formaldehyde without exposure to these substances did not experience an elevated mortality from lung cancer. The risk did not increase with cumulative levels of formaldehyde among those exposed to other substances and there was a slightly negative trend for those exposed to formaldehyde alone. Although some role for formaldehyde, particularly in association with other substances, in the excess of lung cancer seen among these workers cannot be ruled out, these findings suggest that exposure to phenol, melamine, urea, wood dust or other exposures also occurring in the area where these substances were used (i.e., production of resin and molding compounds) may play a more primary role. This association should be further evaluated in other studies that include workers from resin and molding compound operations.