The rate of mercury contamination in tuna and other Pacific fish has increased 30 percent since 1990. The increase is a direct result of China's rapid industrialization, and the mercury content is expected to increase another 50 percent by 2050 if China continues to build more coal-fired power plants.
The data comes from a new study by the U.S. Geologic Survey.
About 40 percent of all U.S. exposure to mercury comes from eating contaminated tuna from the Pacific. Roughly 75 percent of all human exposure to mercury in general comes from eating fish. Mercury poisoning early in life, even in very small amounts, can lead to permanent developmental effects.
Mercury becomes toxic when it is converted by bacteria into a form called methylmercury. Scientists have long known how this conversion takes place in freshwater lakes, reservoirs and rivers, but this study is the first to document how that conversion takes place in the ocean. It shows that methylmercury is produced in mid-depth ocean waters by bacteria decomposing settling algae.