Junkfood Science: Booster shots with mercury?

July 24, 2007

Booster shots with mercury?

It’s time for another critical thinking booster shot... for the media. No matter how many times science injects a dose of reality to refute hair-raising claims, the shots last only a short while before the media is trying to scare us again — using the exact same claims! Saddest of all, the scares needlessly target young parents who are naturally concerned for the welfare of their babies and children.

Here we go again with headlines reporting on “high” mercury levels that aren’t really high.

Employees at the Division of Environmental Health at New York City Department of Health & Mental Hygiene performed biomonitoring tests on 1,811 New Yorkers for levels of mercury and other metals in their blood. The results were just published in Environmental Health Perspectives Online. The findings reported by the New York Times were spun to sound frightening and especially dangerous for women and babies:

High Mercury Levels Found in One-Fourth of Adults

One-quarter of adult New Yorkers, roughly 1.4 million people, have elevated levels of mercury in their blood, mainly from eating certain fish.... The elevated mercury levels that were found pose little, if any, health risk for adults, but may increase the risk of neurological damage in fetuses and infants whose mothers pass on the mercury through their bloodstreams during pregnancy or through breast milk....

Nationally, said Mr. Kass, research showed that about 10 percent of women of childbearing age had blood mercury levels at or above five micrograms per liter, the threshold considered the low end for potential health risks....The survey, conducted among 1,811 adults in 2004, found that one-quarter of women ages 20 to 49 had a blood mercury level at or above five micrograms per liter, while nearly half of Asian women had a blood mercury level at that threshold.

The department’s report linked the higher mercury levels among Asians to eating more fish, finding that foreign-born Chinese New Yorkers eat an average of three fish meals a week, compared with about one a week among New Yorkers over all. About one-quarter of Chinese New Yorkers eat fish five or more times a week....

We’ve covered this scare numerous times, so there’s no need to rehash the science in detail again...just a quick little painless booster shot of reality.

As we know, there is no evidence that levels of methylmercury in the fish Americans consume is cause for health concerns. In fact, the U.S. Centers for Disease Control continually finds that American women of childbearing age are many times below exposure levels even speculated as possibly posing risks for themselves or their babies.

Reading today’s media stories, however, we’re led to believe that 5 micrograms per liter — that’s parts per billion — found in the blood is “high.”

It’s not.

It is every bit as negligible as it sounds. Homeopathic levels of “active” ingredients, in fact.

The EPA’s risk assessment, the most conservative in the world, has set its benchmark dose at 58 parts per billion in the blood — more than ten times the “high” level reported in this story.

What’s a benchmark dose? As Dr. Joseph Jacobson, of Wayne State University and a member of the National Academy of Sciences’ Committee on Methylmercury, explained, the benchmark dose is “the lowest dose they thought safe from any effect over a lifetime of daily exposure in the most sensitive population of children.” They then added in an arbitrary ten-fold safety factor to that, to arrive at a “reference dose” which they use for regulatory reporting. But reporting thresholds are not the same as health risks.

Here’s that adage about ‘the dose makes the poison’ again. While a physiological basis for the neurodevelopmental effects of toxic levels from mercury poisoning is understandable — as seen in the Japanese spills during the 1950s where blood levels were a hundred times the New Yorkers in this study — there is no biological basis why our natural, low-level exposures would pose any risks, according to methylmercury toxicology expert Dr. Gary J. Myers, M.D., at the University of Rochester Medical Center, in Rochester, NY.

The participants in this study were New York residents recruited from four areas of the City and were paid $100 to answer interview questions and provide a blood sample. Most were poor, with the largest group of participants having family incomes under $20,000. The average blood mercury level found among the New Yorkers was 2.73 ppb.

No one came anywhere near the benchmark dose.

Those who had the very highest percentile of mercury concentrations, 2.8% of those tested, had levels of 15 ppb. Still several times below the safe level.

The environmental workers found the highest levels among foreign-born Asians. While claims abound that it must be their high fish diet, these authors didn’t measure the fish eaten by a single person. But more importantly, they didn’t evaluate the use of mercury-containing products, such as medicinals and candles. The Agency for Toxic Substances and Disease Registry, for example, found metallic mercury sold as botanicas and burned in devotional candles by certain ethnic and religious groups had accounted in a number of Americans who tested at the high-end values.

Scientists have found no credible evidence of neurotoxicity or anything remotely resembling brain damage, retardation or learning disabilities even among those eating many times more fish than Americans eat. The FDA Food Advisory Committee held scientific meetings in July 2002 to critically evaluate the evidence on methylmercury and found that, even among populations eating ten times more fish than Americans eat, the most careful research demonstrated no harm to the children’s health or development.

It is easy to become frightened when we hear something might be endangering babies and children. But the fact remains, there is no evidence that American mothers need worry about the methylmercury in the fish they and their children eat. Just as this study showed.

© 2007 Sandy Szwarc

Bookmark and Share