Mercury rising: our seafood is increasingly contaminated with toxins

E: The Environmental Magazine, July-August, 1998 by Becky Gillette

If, like Oprah Winfrey, mad cow disease has made you swear off hamburgers, you might be eating more fish instead. Fish are touted as a low-fat, healthy food that can help prevent heart disease and other illnesses. But recent reports saying that as little as a half can of tuna per day contains enough mercury to be harmful to developing fetuses, infants and young children make it apparent that dolphin safety isn't your only concern.

Tuna, other seafood and freshwater fish, many experts say, can contain dangerous levels of mercury. The fish are often contaminated by emissions from coal fired power plants, incinerators and other industrial facilities that end up in the water, where mercury turns into its organic form, methylmercury, and accumulates in fish tissue.

"We have very few cases in the environmental community where the detrimental effects are as clear as they are with mercury," says Jackie Savitz, executive director of Coast Alliance, a coalition of 300 environmental groups across the country. "We're looking at over 1,600 fish advisories for mercury in the U.S. in 1996 alone. That means there are 1,600 places where people can't fish out of their local waters safely." Savitz says pregnant women represent the number one risk group for mercury consumption because mercury can cross the placenta.

The second group at most risk is children, because their nervous systems are just developing and are more sensitive to toxic exposure. "Effects at lower levels of mercury contamination are subtle, more obscure and, in a way, more dangerous," Savitz says. "Most people probably know a child who didn't develop neurologically as quickly as he or she should have. Delayed neurological development is actually the result that would be caused by mercury poisoning."

Finding the Source

Coal-fired power plants are the leading source of mercury contamination in the U.S., and represent an estimated 33 percent of mercury emissions. Municipal, industrial and medical waste incinerators contribute another 29 percent to the annual release of about 158 tons of mercury. "The most obvious way to reduce mercury emissions is to stop burning coal," Savitz says. "There are also technologies that remove mercury at the stack level."

"Electric utilities are getting a free ride on their mercury pollution," agrees Peter Morman, a policy associate with the Environmental Law and Policy Center. "While other sources are cleaning up, there are no requirements for power plants to cut their emissions."

Newer technologies and waste segregation could reduce mercury emissions from another major source. Health Care Without Harm (HCWH) is encouraging hospitals to replace medical devices with nonmercury alternatives. For example, many hospitals are switching to non-mercury thermometers. Another focus of reform is simply good housekeeping: requiring mercury to be separated out so it doesn't end up in an incinerator--and then in fish that people eat. The State of New Jersey insists that mercury in hospitals be segregated, and this has reduced that state's medical waste mercury emissions a hundred fold.

The Specter of Dioxin

Besides mercury, PCB and dioxin contamination of fish is also a concern. All three Compounds have harmful effects on developing fetuses and infants, and are passed from mother to child both through the placenta and breastfeeding, according to Dr. Amy Kyle, principal author and researcher of Contaminated Catch: The Public Health Threat from Toxics in Fish, published last April by the Natural Resources Defense Council (NRDC).

"Methylmercury is a potent neurotoxin that affects the nervous system and brain development," Kyle says. "PCBs affect the mental and physical development of children and are thought to cause cancer. Dioxins have reproductive, developmental, and immune system effects and are one of the most potent carcinogens ever tested on animals."

Toxic fish can be a problem no matter where you live, and the amount and types of contamination can vary widely depending on the species and size of the fish. The Great Lakes states are highly impacted, and have the largest number of fish ad visories. But mercury also tends to accumulate in reservoir fish, which may be a concern in Western states. where reservoir fishing is common and water testing is not performed regularly.

Campaigns to draw attention to mercury and other toxins in fish have drawn criticism from seafood industry representatives, who say the public shouldn't be scared away from eating a healthy source of protein. Kyle responds that while eating fish can reduce the incidence of heart disease, diabetes and other chronic diseases, fish are also the most significant source of mercury and PCBs that people absorb into their bodies.

"The contaminants found in fish have been linked to a number of long-term health effects, including problems with the reproductive system, development, intelligence and the balance of the hormones in our bodies," Kyle says. "Several toxic compounds cause cancer. Some damage the immune system so that it is less capable of fighting off disease. Others affect the nervous system.