Tissue Distribution of Substituted Diphenylamine Antioxidants and Benzotriazole Ultraviolet Stabilizers in White Sucker (Catostomus commersonii) from an Urban Creek in Canada

Substituted diphenylamine antioxidants (SDPAs) and benzotriazole ultraviolet stabilizers (BZT-UVs) have been detected in aquatic organisms, but little is known about their tissue distribution and elimination in wildlife. This study investigates the distribution of SDPAs and BZT-UVs in blood plasma, bile, liver, and carcass (without gill and internal organs) of white sucker (Catostomus commersonii) and evaluates the extent of biliary excretion in fish. Fish were collected from a creek upstream and downstream of an urban area in Ontario, Canada. Downstream fish showed levels of contamination of many target compounds [e.g., 4,4'-bis(alpha,alpha-dimethylbenzyl)diphenylamine and monononyl-diphenylamine] higher than those of upstream fish, indicating the input of these contaminants from the urban area. The concentration (wet weight) of target compounds generally decreased in the following order: liver > carcass homogenate >= bile > plasma. This indicates that liver is a major tissue for accumulation of these contaminants in fish. Tissue-specific partition coefficients suggest that SDPAs tend to partition from plasma to liver and that the biliary excretion of these contaminants is a relatively minor pathway of elimination. Only monobutyl-diphenylamine was effectively excreted via bile. Our results suggest that future studies should focus on the liver toxicities and biotransformation of these contaminants to improve our understanding of their environmental risks.