UPDATE OF THE MORBIDITY EXPERIENCE OF EMPLOYEES POTENTIALLY EXPOSED TO CHLORPYRIFOS

Objectives-Chlorpyrifos, an organophosphate ingredient of several impo rtant insecticides, has been manufactured at The Dow Chemical Company for 25 years. A previous morbidity study among employees of The Dow Ch emical Company found no increased prevalence of illness or symptoms am ong employees potentially exposed to chlorpyrifos from 1977 to 1985 co mpared with matched controls. The purpose of the current study was to update the original study to 1994, thereby increasing the statistical power. Methods-In the present study 496 potentially exposed subjects w ere identified and matched for age, race, sex, pay, and year of hire t o 911 control subjects. Morbidity data were abstracted from company me dical records. Results-The prevalence of peripheral neuropathy was not significantly increased among this group of employees potentially exp osed to chlorpyrifos, Significantly increased prevalence odds ratios w ere identified for five diagnostic categories: diseases of the ear and mastoid process; acute respiratory infections; other diseases of the respiratory system; general symptoms, signs, and ill defined condition s; and symptoms, signs, and ill defined conditions involving the diges tive system. There was a strong association of diagnosis with duration of observation period, indicating that the exposed workers were more Likely than unexposed workers to have a diagnosis abstracted from the company medical records due to their longer mean period of follow lip. Analyses by exposure classification and mean plasma cholinesterase ac tivity did not show a dose response. Conclusions-These data do not sup port a cause and effect relation of the diagnoses mentioned and exposu re to chlorpyrifos.