September 24, 2008 – Women in the Northeast are contaminated with the highest concentrations of mercury in the United States, with one of every five exceeding levels considered safe for fetuses, according to a new national study.
Mercury levels in Americans
The study, led by U.S. Environmental Protection Agency scientist Kathryn R. Mahaffey, is the first regional look at mercury concentrations in women of childbearing age.
Mercury is a potent neurotoxin that accumulates in fish and seafood. When babies are exposed to high concentrations of mercury in the womb, their brains may develop abnormally, impairing learning abilities and reducing IQ.
Nationwide, one of every ten women—nearly 7 million women—exceeded the mercury concentration that may pose a risk to fetuses, according to the new report, published online in Environmental Health perspectives on Aug. 25.
The good news is that mercury concentrations are declining in American women, according to the report, which analyzed data collected between 1999 and 2004.
Mercury exposure varies widely across the country because of differences in how often fish is consumed.
Women along the Atlantic coast had the highest levels in their blood, followed by women living on the Pacific coast. The lowest levels were in inland areas of the Midwest and West. Those living in the Great Lakes region, the inland Northeast and the inland South were in the middle.
“Women living near the coastal areas have approximately three to four times greater risk of exceeding acceptable levels of mercury exposure than do non-coastal dwelling women,” the authors wrote.
Some were very highly exposed. Five percent of women along the Atlantic coast had levels that were more than three times the amount that may harm a fetus.
Mahaffey and her colleagues reported that the higher mercury levels in Northeastern women reflect their more frequent fish and shellfish consumption. But they theorize that it also could mean that some of the fish they are eating are more highly contaminated than fish eaten elsewhere.
In addition, women who are more affluent, with family incomes exceeding $75,000, and women of Asian or island ethnicity had the highest mercury levels.
Mercury concentrations are declining substantially in American women even though they are eating the same amounts of fish, according to the study authors.
In 2003-2004, the latest data available, about 2.5% of women exceeded the EPA’s guideline of 5.8 parts per billion of mercury in their blood, compared with 7% in 1999-2000, the report says.
Scientists say levels as low as 3.5 ppb may be of concern for fetuses; more than 7% of women exceeded that level in 2003-2004, compared with 14% four years earlier.
Apparently, women are staying away from highly contaminated species, such as swordfish, the authors said.
“This pattern suggests a more discerning series of choices in type of fish eaten rather than an overall reduction in fish consumption,” they wrote.
Federal guidelines established in 2004 advise women of childbearing age to avoid swordfish, shark, tilefish and king mackerel. They also recommend that women eat up to 12 ounces (two average meals) per week of fish and shellfish that are lower in mercury, such as canned light tuna, salmon, pollock and catfish. Canned white or albacore tuna is more highly contaminated and should be limited to six ounces per week, according to the guidelines set by the EPA and Food and Drug Administration.
The EPA and FDA have tried to balance their warnings about mercury with their fears that women would stop eating fish. Fish are high in protein and have fatty acids that are beneficial to fetuses, children and adults.
Mercury, in addition to harming the developing brains of fetuses, can be risky for adults, too.
In her new book, Diagnosis Mercury: Money, Politics and Poison, Dr. Jane Hightower, a San Francisco physician, describes how many of her patients suffer from mercury poisoning, experiencing hair loss, severe muscle cramps, headaches, stomach pain, insomnia and memory loss. Some studies link mercury to cardiovascular disease.
Yet, Hightower said, many physicians are unaware of the risks.
“Physicians and consumers need to be ever more diligent as to the types of fish and the quantity consumed, along with contaminant levels,” she wrote.
The scientists analyzed mercury data collected by the Centers for Disease Control and Prevention as part of a national program to test Americans for a variety of chemicals. The new study is the first to analyze regional data, which is not available to the public and is accessible only through a special request from researchers.
The study is at: http://www.ehponline.org/members/2008/11674/11674.pdf
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