Investigating respiratory responses to metalworking fluid exposure

In response to worker and union representative concerns, the association between metalworking fluid exposure and respiratory symptoms was investigated in a cross-sectional survey, in a large automotive machining location. A self-administered respiratory symptom-screening questionnaire was sent to 2935 current employees. MWF exposure levels were assigned to respondents on a departmental basis based on average and "peak" area aerosol measurements. MWF exposure, years in the plant, and smoking status were regressed on presence or absence of daily or weekly respiratory symptoms, as well as upper and lower respiratory symptom groupings derived from principal components factor analysis. The response rate was 81 percent. Symptom prevalence was high: 29 percent of subjects reported weekly or daily phlegm; 23 percent, dry cough; 42 percent, runny or plugged nose. Average aerosol concentration in departments with exposure ranged from 0.02 to 0.84 mg/m(3), and peak levels from 0.02 to 2.85 mg/m(3). Average exposures ranging from 0.25 to 0.84 mg/m(3), as compared to exposures in the range of 0.02 to 0.09 mg/m(3), were statistically significantly associated with wheezing, chest tightness, sore throat, and hoarse throat, as well as with the upper respiratory symptom grouping. When peak exposure was included in the regression, it exerted a stronger effect than average exposure level on dry cough, phlegm, wheezing, fever/chills, and hoarse throat, as well as on upper and lower respiratory symptom groupings. These effects were independent of smoking status. Exposure-symptom trends for the average and peak departmental area concentration categories were statistically significant for the upper and lower respiratory symptom groupings and for most individual symptoms. We have observed an association of increasing upper and lower respiratory symptoms with estimated MWF exposure, measured independently, at average departmental aerosol concentrations well below the NIOSH recommended personal exposure level of 0.5 mg/m(3). The results have been used to prioritize exposure reduction efforts in the workplace.