Although I have lived close to Sudbury for most of my life, I had not heard of the Nyanza Superfund site or the high mercury levels in fish from the Sudbury River until recently. This week, I spoke with some experts about why mercury levels continue to be a health issue, what you should know to avoid it, and how the public can stay informed.

Even though the Nyanza Chemical Site in Ashland was one of the first Superfund sites and was cleaned up during the late 80s and 90s, the level of mercury contamination in fish from the Sudbury River is still a health risk, according to Jim Murphy, spokesperson for the Massachusetts Environmental Protection Agency.

Mercury has settled into the sediment at the bottom of the river, but it can still work its way into the food chain, explained Murphy.

"Little critters bore down in the sediment, then come up and get eaten by fish," Murphy said.

"The fish continue to accumulate mercury," he continued, meaning that when fish absorb mercury, it remains in the tissues and is not excreted. "Larger fish are more of a problem."

"Mercury is particularly hazardous for children and women who are pregnant," said Martin Pillsbury, the manager of environmental planning at the Metropolitan Area Planning Council. "The worst effects are on developing nervous systems."

According to the EPA website, mercury exposure can affect the "cognitive thinking, memory, attention, language, and fine motor and visual spatial skills" of children who were exposed to mercury in the womb.  Other effects of mercury include tingling sensations in the feet and hands, "lack of coordination of movements; impairment of speech, hearing, walking; and muscle weakness," according to the EPA website.

Even though mercury causes many symptoms in humans, it is not possible to tell if a fish is contaminated with mercury in it just by looking at it, explained Pillsbury. The mercury is "tasteless, odorless, so people don't realize they're getting it when they're eating the fish" he said.

The EPA has posted signs along the Sudbury River warning fishers not to eat the fish in three languages, and Murphy said the EPA plans to maintain the signs and continue to work with other organizations to warm the public about the mercury risk. The Metropolitan Area Planning Council created a campaign called Fishing4Health, which includes a website, radio spots on local Brazilian stations, and articles that were published in the Massachusetts and the Brazilian Times.

Fish from the Sudbury River are not the only source of mercury poisoning. The Massachusetts Department of Public Health recommends that women of child-bearing age and children younger than 12 avoid eating swordfish, tuna steaks, tilefish, shark, or king mackerel, as well as some other types of seafood specific to the Boston area.

For more information about mercury and fish safety, visit http://www.epa.gov/mercury/advisories.htm, www.mass.gov/dph/fishadvisories, and www.fishing4health.com.