Inhalable and Respirable Particulate and Endotoxin Exposures in Kentucky Equine Farms

Adverse respiratory health effects in the agricultural industry have been linked to particulate endotoxin exposure. However, whether the endotoxin concentration is significantly correlated to the size of the particle remains an open question. To date, limited research has been conducted to assess particulate endotoxin exposures in the agricultural industry in general or the equine industry in particular. A task-based exposure assessment was conducted to characterize the endotoxin levels of inhalable and respirable particles on four Kentucky farms during the summer season. We conducted personal sampling of respirable and inhalable particles (n = 75) across all four farms and particulate endotoxin (n = 58) on two of them. Simultaneously, we collected real-time area samples across all four farms by task - horse care, filing hooves, cleaning stalls, cleaning barns, cleaning dry lots, and cleaning trucks. The endotoxin concentration of inhalable particles (geometric mean: 50.2-1,024 EU/m³) was ~50 times higher than that of respirable particles (geometric mean: 1.72-19.0 EU/m³). Horse care generated the lowest endotoxin concentrations for both particle sizes, while cleaning tasks tended to produce higher concentrations. There was no significant correlation between the endotoxin and particle concentrations for each size fraction based on tasks by farm (R² = 0.069 for inhalable; 0.214 for respirable). The equine workers in this study were exposed to higher endotoxin concentrations than workers in other industries, such as the swine industry. Providing exposure control guidelines and recommendations to the equine industry is necessary to reduce long-term endotoxin exposure and to prevent adverse respiratory symptoms.