Heavy metals in Chinese freshwater fish: Levels, regional distribution, sources and health risk assessment

China is a major producer and consumer of freshwater fish, which can provide nutrients to the human body but is also of great concern because of the bioaccumulation and amplification of heavy metals that are directly related to human health. In this paper, we reviewed the accumulation and distribution patterns of lead (Pb), arsenic (As), mercury (Hg), cadmium (Cd), and chromium (Cr) in freshwater fish from 2010 to 2020 in nine basins of China (Yangtze River, Pearl River, Yellow River, Haihe River, Huaihe River, Songhua and Liaohe River, Continental, Southeast, and Southwest basins), assessed the health risks, and compared them with those in Chinese marine fish, international freshwater fish, Chinese wild freshwater fish, and artificially cultured freshwater fish. The results showed that 1) the pollution status of the five heavy metals in freshwater fish from nine basins in China is at an intermediate level internationally; 2) the magnitude of heavy metal concentration in four types of artificially farmed freshwater fish and wild freshwater fish is ranked as follows: rice-farmed fish < cage-farmed fish < pond-farmed fish < lake-farmed fish < wild fish; 3) the noncarcinogenic risk factors for heavy metals in freshwater fish in the nine major basins in China were < 1 for adults, but the noncarcinogenic risk factors for heavy metals in freshwater fish in the Yellow River, Yangtze River, Pearl River, Songhua and Liaohe River, and Huaihe River basins were all > 1 for children.