Endotoxin in Aerosol Particles from Metalworking Fluids Measured with a Sioutas Cascade Impactor

Abstract

Abstract Objectives The aim of this study was to characterize personal occupational exposure to endotoxin in size-separated airborne particles of MWF aerosol, using a Sioutas cascade impactor (SCI). Methods Exposure to inhalable fractions of MWF aerosol and endotoxin was measured by personal sampling of 52 individuals over an 8-h work shift using a PAS-6 sampler in parallel with a SCI (<0.25, 0.25–0.5, 0.5–1.0, 1.0–2.5, and 2.5–10 µm). Aerosol mass concentration was measured for each worker with a real-time instrument (DataRAM) during a full shift. Samples of MWF were collected from the machines and central tanks during the work shift. Results A total of 117 measurements of inhalable MWF aerosols were made among 52 workers. The geometric mean of inhalable MWF aerosol was 0.16 mg m−3 air. The geometric mean of endotoxin concentration on the inhalable sampler was 0.15 EU m−3. Airborne endotoxin was found on all size fractions from the impactor, with the major part seen in the fraction (2.5–10 µm). There was a correlation between the inhalable fraction of endotoxin measured by the PAS-6 sampler and on the SCI sampler (2.5–10 µm), estimated to be 0.51 for all samples (P < 0.0001). The concentration of endotoxin varied between the MWFs, as did the proportion of Gram-negative bacteria among the culturable bacteria (>80% in one MWF and <1.5% in the other three). Conclusions The personal exposure to inhalable fractions of endotoxin contained in the MWF aerosol were low, where most of the endotoxin were found in fraction (2.5–10 µm), measured by SCI. There are differences between factories and MWF systems regarding the distribution of endotoxin and so results from one context should not be generalized to other plants and systems. Compressed air was used for less than 10 min shift−1. The mixed-effect model showed that working with open machines and grinding as cutting task were important determinants of exposure to inhalable aerosol. It is important to keep occupational exposure to aerosols low with the help of good ventilation systems, enclosed machines, and organization of work.