Ecotoxicology of Dioxins in Wild Avian Species

Abstract

　Chlorinated dioxins and related compounds (DRCs) have been found in a variety of environmental matrices, due mainly to their high persistence and bioaccumulation. The regulation on DRCs emission in Japan has been introduced under the “Law Concerning Special Measures against Dioxins” implemented in 1999. Since 1998, the Ministry of the Environment has conducted a nationwide project “Survey on the State of Dioxins Accumulation in Wildlife” in order to understand contamination status and verify effectiveness in the regulation policies. As a part of this project, we investigated contamination status and effects of DRCs in common cormorants (Phalacrocorax carbo) and black-eared kites (Milvus migrans) collected from Lake Biwa and the Kanto district in Japan, respectively. Results showed that DRCs contamination was pronounced in cormorants. In contrast, DRC levels in kites were relatively low. We found congener-specific features of DRCs for hepatic sequestration, maternal transfer through egg-laying, and growth stage-dependent accumulation. In the cormorant liver, expression of cytochrome P450 1A (CYP1A) was induced by DRCs. The present study, together with the whole nationwide projects, showed that while there was a clear decline of the DRCs emission in Japan from the late 1990s as an outcome of the national regulation, tissue levels of DRCs in wild animals were fairly constant over time. Hence, there is a need for a continuous longitudinal monitoring study for accumulation of DRCs and their effects in wildlife.