Mystery at Sea
How mercury gets into tuna and other fish in the ocean has scientists searching from the coast to the floor
- By Eric Jaffe
- Smithsonian.com, September 27, 2007
In the United States and many places around the world, people get a majority of their mercury intake from ocean fish—particularly tuna. Fish has some health benefits, but too much mercury consumption can cause developmental defects in young children. Scientists understand how mercury makes its way into freshwater species, but because oceans are so much larger and deeper, they aren't sure the process is the same.
This uncertainty was underscored in May of 2006, when the San Francisco Superior Court ruled that tuna companies do not have to include mercury warnings on cans. In large part, the decision hinged on whether mercury found in ocean fish originated from man-made industry, such as coal-burning factories that emit the gas, or from a natural location, such as the sea floor. In the court's opinion, two things were clear: No one really knows where ocean fish contract their mercury. And the little that is known suggests it does not come from human pollution.