Occupational Exposure to Endotoxin in PM_2.5 and Pre- and Post-Shift Lung Function in California Dairy Workers

Abstract

Individual exposures to particulate matter and endotoxin in dairies have increased as operations have transitioned to larger herd sizes. A cross-sectional study at 13 California dairies and one non-dairy control facility was conducted to determine associations between endotoxin concentrations measured in fine particulate matter (PM 2.5 ) and respiratory function in these workers. Previous research found that dairy work was associated with acute airway obstruction in comparison to controls. While endotoxin levels in PM 2.5 have been previously reported, their effects on lung function have not been studied among California dairy workers. This paper also examined correlations with PM 2.5 concentration, inhalable particulate matter (IPM), and endotoxin in IPM. Personal samples collected from a total of 185 dairy workers and 45 control workers were included in the analyses. Findings showed that dairy facilities had higher (p < 0.001) endotoxin in PM 2.5 when compared with the control facility (3.3 EU/m 3 , 0.6 EU/m 3 , respectively). Endotoxin in PM 2.5 was weakly correlated with PM 2.5 concentration (r 2 = 0.16, p < 0.05) and IPM endotoxin (r 2 = 0.35, p < 0.01), but not with IPM concentration. When controlling for age, ethnicity, smoking, height and personal protective equipment use, PM 2.5 endotoxin exposure was associated with lower crossshift in forced expiratory volume in 1 second (FEV 1 ) and forced vital capacity (FVC) only among taller workers (p = 0.006). This is the first study to present personal occupational exposures to endotoxin in PM 2.5 measured on Californian dairies. Despite lower levels than in other industries, such as poultry farms, this study suggests that some workers may be affected, and efforts should be aimed at mitigating pollutants in order to maintain endotoxin concentrations below recommended levels.