Background: Despite substantial evidence that workers exposed to metal-working fluids (MWF) have increased respiratory morbidity, the few studies of chronic effects on lung function have not been conclusive.
Methods: Lung spirometry was measured and both current and past exposures to metal-working fluid (MWF) aerosols were estimated in this cross-sectional cohort of 1,811 male automobile workers. Satisfactory exposure data were available for 1,745 (96%): 239 assemblers (never-exposed to MWF), 487 assemblers (previously exposed), 352 machinists currently exposed to straight oils, 441 to soluble oils, and 226 to synthetic fluids. Operations were classified as either grinding or non-grinding machining.
Results: Current exposure was not found to be associated with either forced expiratory volume in 1 second (FEV(1)) or forced ventilatory capacity (FVC). Nor was past exposure to water-based fluids (soluble or synthetic MWF) related to pulmonary function. Past exposure to straight oils, however, was significantly associated with FVC. This association was more obvious among older workers and among workers who had never transferred from MWF exposed jobs to assembly.
Conclusions: The magnitude of the association between FVC and lifetime exposure to straight MWF was slightly larger than the estimated cigarette effect, suggesting that the impact of an additional year of exposure to 1 mg/m(3) of mineral oil particulate in the thoracic particle size range, has the same impact on FVC as smoking one pack per day for one more year.