One well-known tale of this type of behavior took place in Japan in the 1950s and '60s. As a result, more than 2,000 people got mercury poisoning related to fish that had been caught in Minamata Bay. Eco Watch says that this is why the neurological syndrome associated with massive mercury poisoning has been named Minamata disease. 

Eco Watch says that these concerning behaviors have also been seen in American waterways. For example, Allied Chemical Company dumped up to 20 pounds of mercury into Onondaga Lake (located in New York) on a daily basis at one time. 

Plus, the burning of fossil fuels results in mercury issues when mercury finds its way into the air supply. Experts say that this mercury eventually finds its way to the ground, and then into the ocean by way of rain. It then makes a conversion from elemental mercury to methylmercury. At this point, it is thought to make its way into the food chain, starting with the tissues of the smallest creatures and then working its way up the food chain to humans. 

But what about tuna?

You may have heard that tuna is a large concern. This is said to be because tuna is a predator, making it possess the ability to be high in mercury. Consequently, some health experts say that pregnant women should avoid tuna altogether to eliminate health risks. 

“Canned tuna contributes more than one-third of the mercury exposure of the average American,” Philippe Grandjean, M.D., tells Time. “About one in six women in coastal U.S. populations have elevated mercury exposures that could cause harm to the fetus.” 

But this doesn’t mean that you will develop mercury poisoning from eating seafood. According to the United States Environmental Protection Agency (EPA), this shouldn’t be a concern for the majority of people. However, some people are in a higher risk group than others. For example, women who are pregnant, children and elderly people fall into this category. Plus, some people’s risk increases because they consume large amounts of fish in general.