Mercury Rising

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 non-mercury 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 requires 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 advisories. 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 said. “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.

“People who eat fish are being forced to make sense out of complicated and sometimes contradictory warnings, and to calculate for themselves how many servings of different kinds of fish are safe to eat. People who are catching their own fish, either through sport subsistence fishing, need to find out if state or county health departments have issued advisories. That will tell them what species and what areas are more likely to be contaminated, and that they should either avoid or limit their consumption.”

While fish caught in contaminated waterways are of concern, tuna in the can is considered the biggest risk because of its wide availability and consumption. Testing by the FDA revealed that 100 percent of samples of oil-packed tuna contained mercury. The FDA also found mercury in the other most common seafood available at the supermarket: in about 90 percent of commercial haddock and shrimp, and in 75 percent of frozen fish sticks.

Toxins in fish can also poison birds, marine mammals and other wildlife, and are an indication that persistent toxic chemicals are accumulating in the environment.

What You Can Do

Consumers who want to eat fish without fear should voice their concerns about mercury and other pollutants to elected officials on the state and federal level. They should urge the reduction of emissions from power plants, and the closure of incinerators that release dioxins, PCBs and mercury. It is possible to reverse this trend: Cleanups of contaminated waterway sediments remove the pollution, so it is no longer available to the bottom feeders (like catfish, for example) which pass it along up the food chain. States should also be encouraged to improve monitoring, and do a better job informing the public about fish advisories.

Sportsmen should avoid fishing in waters that have advisories—and be careful about what they take home to eat. (In general, smaller and younger fish, with plant-based diets, are less contaminated than big carnivores like tuna and swordfish.) A

nd don’t think you’re safe because your fish was “farm-raised.” Airborne mercury deposited in steams and rivers can also land on a fish farm pond. And there are other concerns about aquaculture such as use of antibiotics and other feed additives at fish farms.

This cautionary information shouldn’t steer you away from eating seafood altogether. But women of childbearing age and young children should eat tuna only in moderation, and make informed choices about other seafood. Discretion is advised.

BECKY GILLETTE is a freelance writer in Ocean Springs, MS.