Change in airway responsiveness among apprentices exposed to metalworking fluids

To investigate early pulmonary responses to metalworking fluid exposure, we enrolled first-year machinist apprentices and apprentices in three other t rades into a 2-yr longitudinal study. We obtained complete data for 82 mach inists and 159 control subjects. Tests included respiratory questionnaires, spirometry, methacholine challenge, and allergy skin tests. Details on dur ation of exposure were collected by interview and 68 representative full sh ift personal samples for "total aerosol" were obtained from 13 shops (mean: 0.46 mg/m(3), range: < 0.7 to 3.65 mg/m(3)). Machinists and control subjec ts did not differ at baseline. At follow-up, average change in bronchial re sponsiveness was double in machinists compared with control subjects (p = 0 .05), and machinists were more likely to have developed new bronchial hyper responsiveness (BHR) with asthmalike symptoms. In linear regression analysi s, for predictors of methacholine slope, increased BHR was associated with duration of exposure to both synthetic and soluble metalworking fluids (p < 0.05); in logistic regression analysis, for predictors of BHR, only durati on of exposure to synthetic fluids was a significant predictor. Results wer e not changed when workers with PC20 < 8 mg/ml at baseline were excluded. W e conclude that exposure to water-based metalworking fluids (especially syn thetic fluids) is associated with increasing BHR during the first 2 yr of e xposure.