EXPOSURE ASSESSMENT FOR A FIELD INVESTIGATION OF THE ACUTE RESPIRATORY EFFECTS OF METALWORKING FLUIDS .1. SUMMARY OF FINDINGS

The exposure assessment summarized here is part of an epidemiologic st udy of the acute respiratory health effects of metalworking fluid (MF) exposures. Exposures were measured as the inhalable concentrations of the MF aerosol, a variety of metals and elements, and endotoxin as we ll as the level of culturable bacteria in the aerosol size fraction le ss than 8 mu m. Bulk samples of soluble MFs were tested for pH, minera l and tramp oil fraction, endotoxin, culturable bacteria, and lipopoly saccharide levels. The MF exposed workers had higher geometric mean in halable aerosol exposures (0.181 mg/m(3)) than the MF unexposed worker s (0.046 mg/m(3)). The MF exposed workers had higher geometric mean (G M) airborne culturable microbial counts (102 colony-forming units (CFU )/m(3) for bacteria <8 mu m) than the unexposed workers (GM=14 CFU/m(3 )). Among the unexposed, Bacillus was the predominant airborne species , while among the exposed workers, Pseudomonas predominated. Exposed w orkers also had higher geometric mean airborne endotoxin levels (GM=7. 1 endotoxin units (EU)/m(3) than the unexposed workers (GM=1.9 EU/m(3) ). Elemental concentrations of iron, chlorine, and sulfur were substan tially higher among the exposed workers compared to the unexposed work ers, for soluble metalworking fluids, the levels of bulk constituents were examined by three categories of time since the machine sump was r efilled with fresh MF (<4 days, 4-21 days, >21 days). Univariate analy ses of percent oil, pH, culturable bacteria, tramp oil percent, endoto xin, or Fatty acid levels all showed no statistically significant chan ges in level over time.