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Like lead, mercury is another natural metal that has significantly increased in our environment as a result of human activities. Most of the mercury in Maine comes from emissions from coal-fired power plants both near and far. Sources of mercury within the state include trash waste incinerators, wood and fuel oil boilers, the breakage and disposal of mercury-containing products such as fluorescent light bulbs (including compact fluorescents), thermostats and thermometers, and dental amalgam fillings. Mercury is released into the air, where it drifts with prevailing winds and falls out of the sky in dust, rain, and snow, and settles onto land or the ocean. Once on land, mercury is washed into streams and lakes, where it is converted to its more toxic and available form, methylmercury, and builds up in the food chain.

We are exposed to mercury mainly by eating contaminated fish, especially tuna but also shark, swordfish, tilefish, and king mackerel, which have the highest concentrations of mercury. Elemental mercury can also be directly inhaled from broken thermometers, dental fillings, and fluorescent bulbs.

Mercury in Maine People

Mercury was detected in the hair of all 13 Maine participants, indicating exposure to mercury over the past four to six months. Fish consumption is the largest source of individual mercury exposure, and this fact may shed some light on the study results.

Mercury levels in these Mainers (median 396 ppb) were generally higher than the national median (200 ppb) reported for 702 women of childbearing age (see Figure 6). Every one of the five Maine women of childbearing age had mercury hair levels greater than the national median level (see Tables 2 and 3).

The amount of methylmercury measured in the hair of House Majority Leader Hannah Pingree was above the U.S. EPA-established reference dose for mercury, which is the level above which the developing brain of the fetus may be harmed due to maternal mercury exposure. Hannah Pingree, Elise Roux, and Lauralee Raymond all reported eating tuna in sushi or swordfish at least twice a month, which may explain their elevated mercury levels.

Eric Stirling had the highest mercury level in the group, a level much greater than the national median. Eric reported that he commonly ate fresh-caught brook trout. While brook trout are not usually considered to be high in mercury, it is possible that Eric's lifestyle as a sporting camp owner means he eats more local, freshwater fish than the average Mainer. It's also possible that Eric fishes in streams or ponds that are particularly polluted with mercury, but such analysis was not part of this study.

Figure 6: Methylmercury levels measured in hair


Mercury is a potent neurotoxin. Responsible for “mad hatter” syndrome, mercury can cause birth defects and brain damage, learning disabilities, loss of vision and blindness, kidney damage, numbness, and lack of coordination. The developing brain of babies in the womb, nursing infants and children are especially vulnerable to mercury. The adverse effects of prenatal mercury exposure, even at low levels, include deficits in memory, attention span, motor control, and the ability to learn. According to the EPA, eight percent of women of childbearing age in the U.S. have elevated blood mercury levels of concern for fetal development. The EPA estimates that 630,000 infants born each year in the United States are at risk for neurological damage from exposures to methylmercury.

Policy Changes Needed

The policy goal to virtually eliminate mercury from manmade sources was adopted by the New England Governors and Eastern Canadian Premiers in 1998. Since then a number of medical waste incinerators and trash combustors have been closed and many of those remaining have upgraded air pollution controls. Maine has also banned the sale of many mercury-containing products including blood pressure monitors, thermostats, and electrical switches; and required that mercury products be labeled and recycled at the end of their useful life.

Aggressive actions are needed to reduce mercury emissions from coal-burning power plants and to reduce reliance on coal and fuel oil in favor of low- or no-mercury power and heat sources. More efforts are needed to warn people of hazardous levels of mercury in swordfish, canned and raw tuna, and other fish that are higher in mercury or consumed in large quantities. Restaurants and grocery stores should be required to advise women who may become pregnant and young children to avoid fish high in mercury.

Manufacturer responsibility to pay incentives for mercury product recycling need to be extended beyond old automobile switches and thermostats to include fluorescent light bulbs and other mercury products. Efforts to replace mercury-containing fluorescent lighting with even more energy efficient digital lighting should be accelerated.

Reducing Your Exposure to Mercury

Eat fish that are low in mercury. Nearly all fish and shellfish contain traces of mercury, but some have more mercury than others. Women who are or may become pregnant should avoid eating swordfish and tuna (canned, steaks or in sushi). (See Maine’s fish consumption advisory and visit

Recycle old mercury products. Contact your town about the hazardous waste collection schedule for recycling fluorescent light bulbs, thermostats, and other mercury-containing products. Carefully handle and thermometers, fluorescent light bulbs and other mercury products to avoid breakage prior to recycling. Do not vacuum up spilled mercury, because it will vaporize and your exposure will increase drastically.

Support mercury-free dentistry. Ask for composite fillings instead of “silver” fillings or amalgam, which are about 50% mercury. If you have metal amalgam fillings, consider having them replaced with composite fillings.

Demand that utilities slash mercury from coal-burning. Support Maine legislative efforts in conjunction with other New England states to force the federal government to reduce mercury emitted by coal fired power plants, as required by the Clean Air Act.

Fish Consumption Advisory

BioDiversity Research Institute
All of Maine's lakes, ponds, and rivers are under a fish consumption advisory due to mercury pollution. According to the Maine Center for Disease Control and Prevention, women who are pregnant, nursing, or may become pregnant, and children under age 8 should eat no freshwater fish from Maine's inland waters except for one meal per month of brook trout or landlocked salmon. All other adults and children older than 8 can eat one to two fish per month from Maine lakes and rivers.

The State also advises that pregnant and nursing women, women who may get pregnant, and children under age 8 limit their consumption of canned light tuna to 2 meals per week or white tuna to 1 meal per week; all other adults and children age 8 and older can eat 2 meals per week of canned tuna.

Other public health advocates suggest that pregnant and nursing women should avoid all canned tuna (and tuna in sushi) because the advice above will result in mercury exposures to the fetus that exceed the federal reference dose or safety level established to protect the children’s health from neurotoxicity.


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