Effects of production practices and environmental factors on air contaminants in swine facilities

Workers in the swine industry are frequently exposed to respiratory hazards including organic dusts, bioaerosols, gases, and endotoxin. The objective of this research is to characterize air contaminant concentration and variability associated with differing swine rearing practices.

We measured air contaminant concentrations once per month for a year in a facility with parallel sow/farrow rearing systems (gestation crates and open gestation pens), and in finishing pens using dry and wet feed delivery systems. Measurements were made on days when pigs were being moved and not moved. Time- weighted average respirable dust and endotoxin concentrations were measured at stationary locations. Respirable dust, hydrogen sulfide (H₂S), ammonia (NH₃), and carbon dioxide (CO₂) concentrations, and temperature and relative humidity were measured with direct-reading instruments to assess temporal and spatial variability. We compared average and peak contaminant concentrations and the spatial distribution of concentrations as a function of the type of production system.

Individual contaminants were largely below occupational exposure limits. Exposures to hydrogen sulfide did exceed exposure limits (2.11 vs. 1.0 ppm) one day due to power washing. This episode included an excursion above the short-term exposure limit (5.19 vs. 5 ppm). Although concentrations were rarely greater than ½ of occupational exposure limits for individual contaminants, concentrations for multiple contaminants approached limits calculated for mixtures in the winter months when ventilation was reduced. Differences in air contaminant concentrations between gestation crate and pen configurations for sow housing, were small with pens being slightly, but not significantly, higher. Endotoxin levels increased on days animals were moved. Dry feeding areas exhibited higher concentrations of endotoxin and hydrogen sulfide. Facility ventilation was reduced in winter months leading to significantly higher exposures of all contaminants. In summer months, the average daily temperature in the barns exceeded 30ºC on some days, potentially leading to a heat stress risk.

Air contaminant concentrations did not differ substantially between sow housing using gestation crates or open pens. Utilization of a wet feed delivery system reduced exposure to some contaminants. Lower ventilation rates during cold weather led to significantly higher concentrations, suggesting that exposure monitoring during cold weather is critical for occupational health surveillance. Heat exposures during summer months may put workers at risk of heat stress. The effect of these exposures on workers or the animals has not been well characterized.

DS Murphy, PC Raynor, S Engelman, G Ramachandran, JB Bender, BH Alexander. Effects of production practices and environmental factors on air contaminants in swine facilities. 2014 Allen D. Leman Swine Conference.