Exposure Assessment for a Field Investigation of the Acute Respiratory Effects of Metalworking Fluids. I. Summary of Findings

Abstract

The exposure assessment summarized here is part of an epidemiologic study 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 well as the level of culturable bacteria in the aerosol size fraction less than 8 microns. Bulk samples of soluble MFs were tested for pH, mineral and tramp oil fraction, endotoxin, culturable bacteria, and lipopolysaccharide levels. The MF exposed workers had higher geometric mean inhalable aerosol exposures (0.181 mg/m3) than the MF unexposed workers (0.046 mg/m3). The MF exposed workers had higher geometric mean (GM) airborne culturable microbial counts (102 colony-forming units (CFU)/m3 for bacteria < 8 microns) than the unexposed workers (GM = 14 CFU/m3). Among the unexposed, Bacillus was the predominant airborne species, while among the exposed workers, Pseudomonas predominated. Exposed workers also had higher geometric mean airborne endotoxin levels (GM = 7.1 endotoxin units (EU)/m3) than the unexposed workers (GM = 1.9 EU/m3). Elemental concentrations of iron, chlorine, and sulfur were substantially higher among the exposed workers compared to the unexposed workers. For soluble metalworking fluids, the levels of bulk constituents were examined by three categories of time since the machine sump was refilled with fresh MF (< 4 days, 4-21 days, > 21 days). Univariate analyses of percent oil, pH, culturable bacteria, tramp oil percent, endotoxin, or fatty acid levels all showed no statistically significant changes in level over time.

Microbial and Endotoxin Contamination of Water-Soluble Metalworking Fluids

“…According to Laitinen et al [5], average concentrations of viable bacteria equalled from 10 5 to 10 8 CFU/ml, with the highest concentration level of 10 10 CFU/ml. Similar ranges are also quoted by Woskie et al [14] and Foxal-VanAken et al [15]. The coolants examined were considerably less contaminated with moulds.…”

Hypersensitivity pneumonitis in a metal‐working environment

“…The authors could identify no clear relationships between measures of contamination and airborne exposure. In addition, despite the obvious presence of hypersensitivity pneumonitis, no association with any single organism could be identi®ed, although the range of organisms resembled that of other reports [Rossmore, 1981;Mattsby-Balzer et al, 1989;Lummus et al, 1998] and similar exposures were identi®ed [Thorne et al, 1996;Woskie et al, 1996]. Despite intense and aggressive searching, no evidence supported Mycobacterium chelonae as a cause of this outbreak.…”

A Model for Predicting Endotoxin Concentrations in Metalworking Fluid Sumps in Small Machine Shops

“…Worse, 6% of the sumps examined in this study had never been cleaned or had MWF completely replaced. Interestingly, Woskie et al (1996) were able to investigate this issue, but found that pH, tramp oil concentration and endotoxin concentrations were not affected by how recently soluble sump fluids were changed (<4 days, 4-21 days, >21 days).…”

“…Milton and Johnson (1995) reported a range of sump endotoxin concentrations of 13 100-124 000 EU/ml in two automotive plants. Woskie et al (1996) conducted a study in automotive parts manufacturing facilities where machines had independent sump systems and were run intermittently. The GM MWF sump endotoxin concentration was 39 000 EU/ml.…”