Exposure to metalworking fluid aerosols and determinants of exposure

Metalworking fluid (MWF) aerosols are associated with respiratory disorders including asthma and hypersensitivity pneumonitis. The aims of this study were to describe exposure to inhalable MWF aerosols and volatile compounds in machine shops, to estimate the influence of important determinants of exposure and to compare different sampling techniques for MWF aerosols. Personal full-shift air samples of inhalable aerosol (PAS-6 sampler) and total aerosol (open-faced sampler) were collected on operators in five medium to big-sized machine shops in three companies. The filters were analysed gravimetrically and extracted by supercritical fluid extraction for MWF aerosol and triethanolamine content. In addition, personal measurements were taken for formaldehyde and volatile compounds on adsorbent samplers. Continuous dust measurements were performed with a real-time instrument (DataRAM) during 2 h periods, using 1-min average values. In total, 95 measurements of inhalable aerosol and extracted MWF aerosols on 51 operators were conducted. Within the companies, the average exposure to inhalable aerosol ranged from 0.19 to 0.25 mg m(-3) with geometric standard deviations from 1.56 to 1.79. On average, the extracted fraction of MWF aerosol was 67% of the inhalable aerosol concentration. The exposure levels of triethanolamine, formaldehyde and volatile compounds were generally low. About 45% of the between-worker variance could be explained by use of compressed air, lack of complete enclosure of machines or grinding as cutting task. In 21 workers with continuous aerosol measurements, short-term peak exposures during 6% of the work time contributed to approximately 25% of the average concentration of inhalable MWF aerosol. Inhalable MWF aerosol concentration measured with the PAS-6 sampler was a factor 2 higher than the concentrations derived from the open-faced sampler. These findings suggest that control measures, such as full enclosure of machines and the elimination of the use of compressed air as cleaning technique, are required to reduce the exposure to MWF aerosols to levels below the expected threshold for adverse respiratory health effects.