Nested case-control studies of respiratory cancer and nonmalignant respiratory disease among employees at the FMC phosphorus refining plant in Pocatello, Idaho

Results of a retrospective cohort mortality study showed that male employees of the FMC phosphorus refining plant in Pocatello, Idaho experienced more deaths than expected due to respiratory cancer and nonmalignant respiratory disease. Nested case-control studies were conducted to further investigate the possible relationship between occupational exposures at the plant and death due to these two causes.;Past occupational exposures at the FMC Pocatello Plant were compared between cases (members of the cohort who died of respiratory cancer or nonmalignant respiratory disease), and selected controls. Controls were chosen from the cohort using incidence density sampling and also were individually matched to the cases by race (white/nonwhite) and date of birth (+/-3 years). Up to six controls were selected per case.;Work histories, including start dates for each job, job titles, gaps in employment, and date of separation of employment for all cases and controls were obtained from available employment records. A job exposure matrix was developed according to the following steps: placing job titles in groups that represented similar exposures; accounting for process and engineering changes that occurred during the history of the plant; and assigning exposure categories of high, medium, low, or none to each job group for each contaminant of interest. Seven workplace contaminants were assessed, including sulfur dioxide, phosphorus pentoxide, polycyclic aromatic hydrocarbons, asbestos, phosphine, dust, and phosphorus.;The job exposure matrix, coupled with the work histories of the cases and controls, were used to describe exposures of individuals. The occupational exposures of cases and controls were then compared and estimates of the rate ratios between exposure and disease were calculated.;No significant relationships were seen between measured exposures at the plant and respiratory cancer. Dust was positively associated with nonmalignant respiratory disease after 30 years of latency. No other measured exposure at the plant was associated with nonmalignant respiratory disease. Limitations in the exposure assessment, small numbers of cases, and lack of information on potential confounding require cautious interpretation of these findings. If improved exposure assessment and sufficient additional cases become available, further investigation is warranted.