Exposure to Inhalable Dust, Endotoxins, β(1→3)-Glucans, and Airborne Microorganisms in Horse Stables

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Abstract
Objectives: Workers in horse stables are likely exposed to high levels of organic dust. Organic dusts play a role in increased risk of inflammatory reactions and are associated with respiratory diseases. The aim of this study was to investigate dust, endotoxin, β(1→3)-glucan, and culturable microorganisms exposure levels in horse stables. Methods: Ambient (n = 38) and personal (n = 42) inhalable dust samples were collected using PAS-6 sampling heads. As a special measurement, we included sampling near the horses’ heads. Samples were analyzed for endotoxin and β(1→3)-glucan by Limulus amebocyte lysate assay and an inhibition enzyme immunoassay, respectively. Culturable bacteria and fungi were collected with an Anderson impactor. Results: Geometric means (GMs) of personal exposure to dust, endotoxin, and β(1→3)-glucan were 1.4 mg m−3 (range 0.2–9.5), 608 EU m−3 (20–9846), and 9.5 μg m−3 (0.4–631 μg m−3), respectively. Exposure levels in the morning shift were higher compared to other shifts. The GMs (ranges) of culturable bacteria and fungi were 3.1 × 103 colony-forming unit (CFU) m−3 (6.7 × 10 to 1.9 × 104) and 1.9 × 103 CFU m−3 (7.4 × 10 to 2.4 × 104), respectively. Variance components for endotoxin and β(1→3)-glucan were considerably higher than for dust. Based on dummy variable in a mixed regression analysis, the predominant task explaining exposure levels of dust, endotoxin, and β(1→3)-glucan was sweeping the floor. For β(1→3)-glucan, feeding the horse was also an important determinant. Conclusion: Dust, endotoxin, and β(1→3)-glucan exposure are considerable in horse stables. Bacterial and fungal exposure levels were moderate. Endotoxin exposures were above the Dutch proposed standard limits, suggesting workers in horse stables to be at risk of adverse health effects.

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