Endotoxins and IgG antibodies as indicators of occupational exposure to the microbial contaminants of metal-working fluids

Objectives: The aim of this study was to evaluate workers' exposure to microbes and bacterial endotoxins during the use of metal-working fluids (MWF). Methods: Air and bulk sampling with biomonitoring of workers' serum IgG antibodies were used to estimate the exposure to biological agents at 18 workplaces. The types of emulsified MWF used were synthetic fluid, mineral oil or rape seed oil, in grinding, turning and drilling work. Results: The endotoxin concentrations in the air ranged from 0.04 to 600 ng/m³ when the endotoxin levels in MWF were 0.03–25,000 ng/ml. A high correlation was found between the endotoxin levels and the bacterial counts from MWF, as well as between the total culturable bacteria and the gram-negative bacteria concentrations in the air. Comamonas testosteroni and C. acidovorans were the most common strains in the samples but also colonies of Ochrobactrum anthropi, Pantoea agglomerans and Stenotrophomonas maltophilia were isolated from the workplaces. Fungi like Aspergillus, Cladosporium and Penicillium species were identified in the air but only rarely in the MWF. Positive IgG antibodies were found in the sera of 22 of the 25 MWF workers examined. Antibodies against S. maltophilia, P. agglomerans and C. acidovorans were the most common, appearing in 72%, 64% and 64%, respectively, of the cases. The MWF workers showed significantly higher IgG antibody responses to bacterial antigens than did the controls. Conclusions: The results clearly proved that in occupational hygiene measurements, endotoxins serve as excellent indicators of exposure to the microbial contaminants of MWF. IgG antibodies against antigens identified from workplace samples could be a practical tool for occupational health physicians. Received: 5 February 1999 / Accepted: 14 June 1999