Risk for Indo-Pacific humpback dolphins (Sousa chinensis) and human health related to the heavy metal levels in fish from the Pearl River Estuary, China.

Cetaceans and humans shared the same route of exposure to many anthropogenic contaminants via fish consumption. To assess the health risks associated with heavy metal levels in fishes from the Pearl River Estuary (PRE) and the seasonal dynamics, 13 fish species (n = 675) consumed by the Indo-Pacific humpback dolphins (Sousa chinensis) and humans were analyzed for concentrations of nine heavy metals. Heavy metal levels vary significantly by species and by season in the PRE fishes. The two eel goby species were the most contaminated fish species, which had the highest levels of Cu, Pb, Hg, Mn and Se. Levels of non-essential metals (As and Pb) in many different fish species were all found significantly higher in dry season than in wet season, which may reflect the dilution effect on contaminant levels in the PRE waters in rainy season. For essential metals, Cu, Cr and Se in many fish species were significantly higher in dry season compared to wet season, while Se and Mn in the other fish species showed an opposite pattern, since essential metal accumulation could be influenced by several physiological processes in life. Risk assessment for dolphins showed that inorganic-As levels in all fishes exceeded the safe limits, whereas a more conservative approach indicated that the levels of all metals in all fish samples had toxic effects on dolphins, except for Hg. Human health risk analysis showed that inorganic-As levels in tonguesole (all year) and sillago (dry season) and Cr levels in pomfret (dry season) exceeded the acceptable values.