Occurrence and Characterization of Steroid Growth Promoters Associated with Particulate Matter Originating from Beef Cattle Feedyards.

Studies of steroid growth promoters from beef cattle feedyards have previously focused on effluent or surface runoff as the primary route of transport from animal feeding operations. There is potential for steroid transport via fugitive airborne particulate matter (PM) from cattle feedyards; therefore, the objective of this study was to characterize the occurrence and concentration of steroid growth promoters in PM from feedyards. Air sampling was conducted at commercial feedyards (n = 5) across the Southern Great Plains from 2010 to 2012. Total suspended particulates (TSP), PM10, and PM2.5 were collected for particle size analysis and steroid growth promoter analysis. Particle size distributions were generated from TSP samples only, while steroid analysis was conducted on extracts of PM samples using liquid chromatography mass spectrometry. Of seven targeted steroids, 17α-estradiol and estrone were the most commonly detected, identified in over 94% of samples at median concentrations of 20.6 and 10.8 ng/g, respectively. Melengestrol acetate and 17α-trenbolone were detected in 31% and 39% of all PM samples at median concentrations of 1.3 and 1.9 ng/g, respectively. Results demonstrate PM is a viable route of steroid transportation and may be a significant contributor to environmental steroid hormone loading from cattle feedyards.