Biodegradation capacity and residue pattern of organochlorines in Ganges river dolphins from India

Concentrations of PCBs (including non‐ortho coplanar congeners), DDTs, HCHs, HCB, aldrin, dieldrin, heptachlor, heptachlor epoxide and chlordanes were determined in river dolphins from the Ganges, India. Residue levels of DDTs were the highest followed by PCBs and HCHs. Noticeable amounts of toxic non‐ortho coplanar PCBs were also detected in the blubber. A continuing exposure of the Ganges biota to organochlorine chemicals was found to be evident. The observed isomer/metabolite pattern indicated that river dolphins exhibit a lower metabolic capacity to organochlorines as documented for other small cetaceans in the marine ecosystem. HCHs and CHLs were considered to be metabolized to a small extent, while PCBs and DDTs were the least metabolizable compounds by river dolphins. The degree of contamination, proximity to pollution source and the metabolic ability of river dolphins found in the present study suggest that river dolphins are at greater risk from environmental contamination by organochlorines than marine cetaceans.