April 2004 Seafood FAQs
Methylmercury poses conundrum for consumers
Here’s how to help them avoid danger, not seafood
The controversy swirling around mercury in seafood, particularly canned tuna, over the last several months has generated headlines and confused more than a few consumers. Here are answers to some key questions you may be asked to help your customers make sense of this complex issue.
Q. How does mercury get into seafood?
Mercury is a naturally occurring element. But human activity has increased the amount of mercury released into the environment. Industrial sources of mercury include mining, burning oil and coal and making steel, cement, agricultural products, paper and pharmaceuticals. Mercury in the atmosphere enters the water, where biological processes transform it into methylmercury, the most toxic form, readily absorbed by fish.
Q. Why do methylmercury advisories target just certain species?
Methylmercury increases in species higher on the food chain, so predatory fish like sharks, tilefish, swordfish and king mackerel have high mercury levels. The Food and Drug Administration and Environmental Protection Agency on March 19 announced a new methylmercury advisory that for the first time specifically addresses canned tuna, because it is the second-most-consumed seafood in the United States (see cover Newsline story).
FDA tested mercury in 3,468 cans of tuna. Albacore/white tuna has 0.358 parts per million of mercury, which is a moderate mercury level. Light tuna has 0.123 ppm of mercury, a low level of mercury.
Q. Is methylmercury dangerous for everyone?
No. Pregnant women, women of child-bearing age, nursing mothers and young children are consumer groups that need to worry about the effects of methlymercury. Toxicologists and public health officials agree that the area of greatest concern is the developing nervous system of unborn children exposed to methylmercury in the mother’s bloodstream. FDA and EPA officials say there also is a risk to a child’s developing nervous system.
Delayed walking and talking and reduced neurological test scores are among the documented problems experienced by children exposed in the womb to relatively high levels of methylmercury, according to the EPA. Those exposed to lower levels exhibit delays and deficits in learning ability.
Q. How big a threat does methylmercury pose to U.S. women?
The Centers for Disease Control in 2001 published a study analyzing blood and hair mercury levels in women and young children and found that the levels are generally below what is considered hazardous. But 10 percent of women had mercury levels within one-tenth of potentially hazardous levels, indicating a “narrow margin of safety for some women and supporting efforts to reduce methylmercury exposure,” says the report.
An EPA researcher in January presented an analysis of mercury levels in fetal umbilical cord bloods, which can be 70 percent higher than levels in the mother’s blood. The analysis showed that 630,000 U.S. newborns had mercury levels greater than 5.8 micrograms of mercury per liter of blood in 1999-2000.
Q. What is the government doing about this problem?
The EPA and FDA in March issued a new methylmercury advisory for pregnant women, women who might become pregnant, nursing mothers and young children.
The advisory was designed so that most women who follow it would have a blood-mercury level no higher than 5.8 micrograms of mercury per liter of blood, says an FDA spokesman. That amount is equivalent to the EPA’s “reference dose” of 0.1 micrograms of mercury per kilogram of body weight per day and is one-tenth of 58 micrograms/liter, the level at which researchers have observed effects in some children. Thus, FDA and EPA built in a tenfold safety factor when designing the advisory.
Women who follow the advisory and eat some combinations of fish with moderately high mercury levels may have blood mercury levels above 5.8 micrograms per liter, but the FDA believes fetuses will still be well-protected from harmful effects.
The advisory also states that fish and shellfish are an important part of a healthy diet because they contain high-quality protein and omega-3 fatty acids and are low in saturated fat. Fish and shellfish can contribute to heart health and children’s proper growth and development, so women and young children should include fish and shellfish in their diets.
Q. Which seafood species are low in mercury?
Based on the FDA’s most recent testing, here are some of the species grouped by amounts of mercury:
Q. Why is the mercury issue so controversial?
Groups like the Environmental Working Group want to see an advisory designed to keep pregnant women’s mercury blood levels at or below EPA’s reference dose of 5.8 micrograms of mercury per liter of blood.
“Given everything that goes into that reference dose, it’s not at all fine for people to be exposed above the reference dose,” says Jane Houlihan, VP of research for the EWG in Washington, D.C. “It’s never been the standard of public health protection to allow significant segments of the population to go above the reference dose.”
Q. Will the new advisory settle the mercury controversy?
No. Environmental and consumer groups want more specific, restrictive advice to give consumers regarding fish that are low or high in mercury. The new advisory would increase the number of women of childbearing age with unsafe levels of mercury in their blood, according to EWG.
Also, the Bush administration is at odds with environmentalists over emissions from coal-burning power plants, the largest U.S. source of mercury contamination.