Airborne particulate matter collected near beef cattle feedyards induces androgenic and estrogenic activity in vitro

Steroid growth promoters are commonly administered to beef cattle residing on feedyards, and a portion of these compounds are excreted in manure along with endogenous steroids. Steroids associated with aerosolized particulate matter (PM) can be transported from feedyards via wind. To assess potential androgenic and estrogenic activity of PM extracts, total suspended particulate samples were collected upwind and downwind of feedyards in the Southern High Plains and subjected to in vitro transcriptional activation assays. Androgen-mediated transcriptional activation induced by exposure to extracts from PM collected downwind of feedyards was significantly higher than that induced by exposure to extracts of corresponding upwind samples, whereas estrogen-mediated transcriptional activation was detected after exposure to upwind and downwind PM sample extracts. Detection and quantitation of metabolites of the synthetic androgen trenbolone acetate downwind, and estradiol both upwind and downwind, suggest that synthetic growth promoters contribute to observed in vitro activity. No significant correlations were observed, however, between individual steroid concentrations or total androgen/estrogen concentration and in vitro activity, indicating the contributions of additional, unquantified compounds to observed androgenic and estrogenic activity. Results indicate that steroids affiliated with feedyard PM have the potential to elicit endocrine-modulating effects.