Exposure to Inhalable Dust, Endotoxins, β(1→3)-Glucans, and Airborne Microorganisms 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 beta(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 beta(1 -> 3)-glucan were 1.4 mg m(-3) (range 0.2-9.5), 608 EU m(-3) (20-9846), and 9.5 mu g m(-3) (0.4-631 mu g 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 x 10(3) colony-forming unit (CFU) m(-3) (6.7 x 10 to 1.9 x 10(4)) and 1.9 x 10(3) CFU m(-3) (7.4 x 10 to 2.4 x 10(4)), respectively. Variance components for endotoxin and beta(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 beta(1 -> 3)-glucan was sweeping the floor. For beta(1 -> 3)-glucan, feeding the horse was also an important determinant. Conclusion: Dust, endotoxin, and beta(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.