Environmental Science and Technology, 50(20):11311-11318, 2016. Paper abstract bibtex
© 2016 American Chemical Society. Research investigating the effects of air contaminants on biota has been limited to date. Captive adult female American kestrels (Falco sparverius) were exposed to a mixture of benzene (0.6 ppm), toluene (1 ppm), nitrogen dioxide (NO 2 ; 2 ppm) and sulfur dioxide (SO 2 ; 5.6 ppm), in a whole-body inhalation chamber. Thyroid axis responses to meet metabolic demands were examined through thyroid histology, plasma thyroxine (T 4 ), and triiodothyronine (T 3 ), and hepatic outer ring deiodination (T 4 -ORD). Plasma free (F) T 3 and T 4 were measured at baseline, and at 9 days and 18 days of exposure, whereas total (T) T 3 and TT 4 , thyroid histology and hepatic T 4 -ORD were determined at the final 18 day exposure. Inhalation of these contaminants significantly suppressed plasma FT 4 and TT 4 , and depleted follicular colloid and increased epithelial cell height at 18 days, and significantly altered the temporal pattern of plasma FT 4 . Significant histological changes in the follicular colloid:epithelial cell height ratio indicated sustained T 4 production and release by the thyroid glands. There was no effect on plasma FT 3 , TT 3 , or hepatic T 4 -ORD. We hypothesize that contaminant-related activation of the hypothalamus-pituitary-thyroid axis in the kestrels increased elimination of plasma T 4 through Phase II enzymes. Further research is required to test this hypothesis in wild birds.