Health of Tree Swallow (Tachycineta Bicolor) Nestlings Exposed to Chlorinated Hydrocarbons in the St. Lawrence River Basin. Part I. Renal and Hepatic Vitamin A Concentrations

Abstract

Sixteen-day-old tree swallows (Tachycineta bicolor), near fledging, were collected in 1999 and 2000 from nine sites representing a gradient of dioxin concentrations, within the vicinity of the St. Lawrence River in Canada and the United States, to determine if organochlorine contaminants correlated with vitamin A levels measured as retinol and retinyl palmitate. Mean concentrations of hepatic retinol ranged from 3mg /kg to 13 mg /kg, and from 0.35 mg /kg to 1.5mg /kg for renal retinol. Mean concentrations of hepatic retinyl palmitate ranged from 18 mg /kg to 146mg /kg, and 1mg /kg to 6mg/kg for renal retinyl palmitate. In 1999, molar ratio of renal retinol:retinyl palmitate was significantly and positively correlated with total polychlorinated dibenzodioxin (PCDD) concentration. Among sites, total PCDDs ranged from 5.4 ng /kg wet weight to 79.5 ng /kg wet weight in tree swallows. These results suggest that current levels of organochlorine contaminants in the St. Lawrence River and surrounding tributaries may be interacting with the vitamin A pathway. Lower circulating levels and higher tissue concentrations of retinoids may result in compromised immune function and reduced reproductive success in adult birds.