Journalist Don Hopey (l) allows Rebecca Lincoln and David Senn to cut a sample of his hair to test for mercury levels.

At the invitation of the Society of Environmental Journalists (SEJ), Spengler and a team of researchers from the Program on Water and Health in the Department of Environmental Health conducted a study of mercury exposure and biomarkers at the society’s annual meeting in Pittsburgh, PA. More specifically, they snipped hair samples from volunteer journalists, sped the strands back to HSPH for processing, and presented preliminary findings before the meeting closed three days later. The information reflected both the chemical analyses and data collected from questionnaires completed by the volunteers.

A total of 260 samples were tested and showed that more than one quarter of the subjects had mercury concentration levels higher than the guideline used by the EPA–1 microgram per gram of hair. The overall results revealed a remarkable difference that spanned three orders of magnitude between the lowest level of less than .001 micrograms per gram of hair and 10.2 micrograms per gram. The average was 0.50 micrograms.

The final report was issued later by Spengler, David Senn, research associate in the Department of Environmental Health, and Rebecca Lincoln, a master’s student. Their partners were SEJ and PennFuture, an environmental organization. The study, funded by the Heinz Foundation, is available at www.hsph.harvard.edu/water/SEJHgStudy.pdf.

"We wanted to try something unusual," said Spengler, Akira Yamaguchi Professor of Environmental Health and Human Habitation. "This approach not only drew attention to issues around a persistent pollutant, methyl mercury, but also made it personally relevant to a group of people who have the ability to raise awareness among Americans about pollution."

Mercury is a naturally occurring element that is used in such banal items as thermometers, fluorescent light bulbs, and tooth fillings. Despite its long history of use, mercury is a toxin, and in recent years, there has been increasing focus on the possible health effects of low-level exposure.

Fish consumption, in particular, has emerged as a lightning rod for discussion. That’s because of the way mercury builds up in fish tissues. When the toxin gets deposited in water ecosystems, some of it ends up transformed into methyl mercury, which is easily absorbed but not easily excreted. Plankton absorb the chemical into their cells before being snapped up by small fish. The small fish accumulate the methyl mercury trapped in the plankton. Larger fish eat smaller fish, building up methyl mercury in their tissues. This "biomagnification" can result in fish that have concentrations of mercury hundreds of times higher than levels in the water where they swim. Some types of fish, such as swordfish, seem particularly vulnerable.

Consumers face a knotty decision when choosing to eat fish. On the one hand, research studies have shown that fish protein, and particularly omega-3 fatty acids, have demonstrated health benefits. The Environmental Protection Agency (EPA) and Food and Drug Administration (FDA) suggest that fish consumption is not a health concern for most people.

On the other hand, fish are a major way in which the average population is exposed to methyl mercury. Both the EPA and FDA have advised that pregnant and nursing women, as well as young children, avoid fish known to accumulate high mercury levels, which can damage developing nervous systems.

Hair is a legitimate biomarker for mercury. As new hair forms under the scalp, it comes in contact with blood and, consequently, circulating methyl mercury, explained Senn, who helped take hair samples. The forming strands incorporate amounts of methyl mercury that are proportional to the levels circulating in bloodstreams. It takes about 30 days for 1 cm of new hair to develop before it pops through the scalp, and so a hair snipped closest to the head reflects methyl mercury levels in the body from the most recent months.

The mercury study found that the number of fish meals a person reported eating was the strongest predictor of mercury levels in hair–the more meals, the higher the level. Average fish consumption was six to seven meals per month. Age was also found to be predictive, perhaps because older people tend to eat healthier meals and perceive fish as a good option, suggested Spengler.

For subjects whose results were high, the study’s authors emphasized that the EPA’s recommendation of 1 microgram per gram of hair is a guideline, not a dividing line between safe and dangerous. However, Spengler is concerned about the potential for growing mercury contamination in the country. Coal- and oil-fired power plants are the largest source of unregulated airborne mercury in the country, he explained. Much of the airborne mercury is transported long distances and gets eventually deposited on land and in aquatic ecosystems. A portion of that mercury is transformed into methyl mercury, which biomagnifies and becomes a risk to both human and ecological health. Forty-one states have issued advisories against certain fish consumption due to mercury poisoning.

"What awful choices we are being asked to make–lower your mercury levels by switching away from beneficial fish, instead of reducing the source of mercury with the currently affordable control technologies for power plants," said Spengler. "It is not just the U.S. power plants that need to be controlled. When you buy the next item made in China, think of the mercury that manufacturing that product is contributing to the Alaskan salmon. And if you enjoy sport fishing in New England lakes, how do you feel when the advisories warn you not to eat what you catch? Mercury in all of us makes environmental degradation real and personal."