SIZE-SELECTIVE PULMONARY DOSE INDEXES FOR METAL-WORKING FLUID AEROSOLS IN MACHINING AND GRINDING OPERATIONS IN THE AUTOMOBILE MANUFACTURING-INDUSTRY

The current metal-working fluid exposures at three locations that manu facture automotive parts were assessed in conjunction with epidemiolog ical studies of the mortality and respiratory morbidity experiences of workers at these plants. A rationale is presented for selecting and c haracterizing epidemiologic exposure groups in this environment. More than 475 full-shift personal aerosol samples were taken using a two-st age personal cascade impactor with median size cutoffs of 9.8 mum and 3.5 mum, plus a backup filter. For a sample of 403 workers exposed to aerosols of machining or grinding fluids, the mean total exposure was 706 mug/m3 (standard error (SE) = 21 mug/m3). Among 72 assemblers unex posed to machining fluids, the mean total exposure was 187 +/- 10 (SE) mug/m3. An analysis of variance model identified factors significantl y associated with exposure level and permitted estimates of exposure f or workers in the unsampled machine type/metal-working fluid groups. C omparison of the results obtained from personal impactor samples with predictions from an aerosol-deposition model for the human respiratory tract showed high correlation. However, the amount collected on the i mpactor stage underestimates extrathoracic deposition and overestimate s tracheobronchial and alveolar deposition, as calculated by the depos ition model. When both the impactor concentration and the deposition-m odel concentration were used to estimate cumulative thoracic concentra tions for the worklives of a subset of auto workers, there was no sign ificant difference in the rank order of the subjects' cumulative conce ntration. However, the cumulative impactor concentration values were s ignificantly higher than the cumulative deposition-model concentration values for the subjects.