Estuarine and coastal ecosystems are usually considered as vulnerable because of the complex biogeochemical processes and the anthropogenic disturbances through a variety of pollution. Among environmental pollutants, heavy metal contaminants in coastal ecosystems have drawn increasing concerns, and related risk assessment has become an important topic for marine environment conservation. Arsenic is a well-known global pollutant, and exists in trace amounts in seawater, sediments, and tissues of marine species. Long-term direct or indirect exposure to high arsenic levels, mainly through drinking water and food, can cause adverse effects on human health. It is crucial to understand the trends and health implications of arsenic levels in popular seafood species, such as oysters. This study investigated the long-term spatiotemporal trends and health risk assessment of oyster arsenic levels in coastal waters of northern South China Sea, in order to help improve the quality and safety control and sustainable aquaculture of oysters in China. Cultured oysters collected from 23 bays, harbors, and estuaries along the coast of northern South China Sea during 1989-2012 were examined for spatial patterns and temporal trends of arsenic levels. Single factor index and health risk assessment were used to quantify arsenic exposure to human health through oyster consumption.
Results/Conclusions
Overall, arsenic was detected in 97.4% of the oyster samples in this study, and oyster arsenic levels were from non-detectable to 2.51 mg/kg with an average of 0.63±0.54 mg/kg. Oyster arsenic levels in the coastal waters of northern South China Sea showed an overall decline from 1989 to 2012, remained relatively low since 2005, and slightly increased after 2007. Oyster arsenic levels in Guangdong coastal waters were much higher with more variation than in Guangxi and Hainan coastal waters, and the long-term trends of oyster arsenic levels in Guangdong coastal waters dominated the overall trends of oyster arsenic levels in the coastal waters of northern South China Sea. Within Guangdong Province, oyster arsenic levels were highest in the east Guangdong coastal waters, followed by the Pearl River estuary and the west Guangdong coastal waters. The single factor index ranged between 0.27 and 0.97, and the health risk coefficient showed a mean value of 3.85×10-5, both suggesting that oyster arsenic levels in northern South China Sea are within the safe range for human consumption. However, long-term attention should be given to the monitoring of seafood market in China and the risk assessment of arsenic exposure to human health through oyster consumption.