government
MERCURY SUMMIT PLANNED New studies, conflicting standards lead federal scientists to examine metbylmercury exposure, risk Jeffjohnson C&EN Washington
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n November, key scientists from a half-dozen federal agencies plan to meet in Research Triangle Park in North Carolina to explore and roundly debate conflicting studies of the effect on humans of exposure to methylmercury, a neurotoxin. The two-and-one-halfday meeting will be public, with presentations by the world's leading mercury researchers, says George Lucier, director of the National Institute of Environmental Health Sciences' Environmental Toxicology Program, who is leading the interagency review. The examination will center on recent studies of developmental problems of children exposed in utero to low levels of mercury. Although the review is intended to help resolve scientific questions—not regulations—its impact will affect standards being developed by federal and state agencies. The uncertainty in science is contributing to differences between allowable levels of mercury in commercial seafood versus sport fish. It also weakens attempts to develop a strategy to reduce mercury air emissions from coal-fired electrical utilities, a primary source. Lucier stresses, however, that the meeting's focus will be on the "science foundation" of regulations and, in particular, studies that examined mercury's impact on the fish-eating people of the Seychelles Islands; a population of the Faeroe Islands, north of the British Isles, that consumes pilot whales; and people subjected to a grain-poisoning incident in Iraq. These three studies are key because each considers the impact of development—walking, talking, and learning— of children exposed in the womb to low levels of mercury. This is a relatively new approach to an old, well-known element. Attending the review will be scientists from the Environmental Protection Agen22 MAY 11, 1998 C&EN
cy, the Agency for Toxic Substances & Disease Registry (ATSDR), the Food & Drug Administration, the White House Office of Science & Technology Policy, the National Oceanic & Atmospheric Administration, and the Centers for Disease Control & Prevention. The meeting and subsequent report, Lucier hopes, will ferret out "what the studies tell us and what they don't." Last December, EPA published a 1,700page, seven-volume report on mercury, the most comprehensive mercury study ever. Although EPA's report looked at sources and a wide range of issues, drawing the most controversy was EPA's reference dose (RfD) for mercury. The RiD is a threshold level at which there is no observed adverse effect. The EPA study set the RiD at 0.1 pg of methylmercury consumed each day for a lifetime for every kilogram of body weight. The EPA RiD includes a safety factor of 10 due to scientific uncertainties. EPA's level is based on the Iraq grainpoisoning incident. It is five times more stringent than levels proposed by ATSDR
Lucier: scientific foundation of regulations
in August 1997 to guide public health officials, and it is also five times lower than an FDA level set to determine allowable mercury content in commercially sold fish. ATSDR's number is based on the Seychelles study and FDA's figure is derived from earlier studies that only considered the impact on adults, says Michael Bolger, a toxicologist and chief of the contaminants branch in FDA's Center for Food Safety & Applied Nutrition. It was "fortuitous" that the ATSDR and FDA numbers match, he says. The implications of the difference in EPA's and the other federal agencies' levels is significant. "If you take EPA's reference dose number at its face value and apply it to commercial seafood, it means shark and swordfish are gone, and half the tuna sold in the U.S. is off the market," says Bolger. "That's a simplistic implication but it is pretty considerable in that you are removing an affordable source of protein from the commercial food supply." EPA's report also could have significant impact on industrial sources that emit mercury to air because air deposition and bioaccumulation in the food chain, especially in marine life, appear to be the primary human entryway. EPA's report found that 50 to 70% of mercury in the atmosphere comes from anthropogenic sources. In the U.S., waste incinerators (53 tons, 33%) and coal-fired utilities (52 tons, 33%) make up the lion's share of the source. Looking at chemicalindustry-related manufacturing, EPA says a very small number of chlor-alkali plants produce 7 tons or 4.5% of all anthropogenic sources. EPA has proposed an emission reductions scheme for waste incinerators that the agency says will cut mercury emissions 90% by 2006. No regulations to reduce mercury emissions from utilities have been proposed; instead, EPA is gathering more information on utilities' emissions—as it has for the past eight years. EPA's mercury report was required in 1994 but was delayed because of scientific questions, opposition by regulated industries, and internal disagreements over the RfD within the government. When issued in December, however, the report had been subject to several favorable outside reviews. The last one, by a panel of outside experts created by EPA's Science Advisory Board, told EPA to issue the report (C&EN, Jan. 5, page 8). Still, the delay stalled development of a plan to reduce mercury emissions by utilities and also led to a delay in a proposal to reduce utilities' emissions of all
air toxics, including mercury, which was required in 1993. In late February, EPA did issue a report on utility air toxics emissions. The report, however, failed to make a regulatory determination, and instead, EPA is calling for more study and will put off a regulatory decision until November. Meanwhile, state public health and environmental officials have begun several programs to limit mercury exposure and to probe the depth of the problem in their locales. State officials are responsible for issuing fishing and public health advisories to limit consumption of contaminated fish, and 39 states have done so for mercury, the most common cause of fishing advisories. In the northeastern U.S. and Canada, environmental officials found that all the states and provinces had issued fish advisories for mercury and most had established levels more rigorous than the FDA standard that bans sale of commercial seafood if mercury exceeds 1 ppm. EPA's RfD is equal to 0.2 ppm. The air, water, and waste officials reported their results in February in "Northeast States/Eastern Canadian Provinces Mercury Study." The report found that average levels in fish are quite near the FDA level where seafood should be rejected, says David R. Brown, a toxicologist for the Northeast States for Coordinated Air Use Management and principal author of the report's health effects section. "State officials' eyes glaze over when you talk to them about these numbers," Brown says, speaking of the FDA/EPA/ ATSDR dose differences. "If you are seeing averages of 0.7 and 0.8 ppm in fish caught in New England lakes, the [federal] numbers are not relevant to the level of the problem. It has not been infrequent that fish in lakes are found to be in the 4- and 5-ppm range." Each state sets its own fish advisory levels based on its interpretation of the science, Brown says, and they tend to favor the "EPA logic" or have added an uncertainty factor to the FDA number, which lowers it. Most state mercury advisory numbers vary from 0.3 to 1 ppm, Brown says, but he notes that state fish advisories usually limit consumption for sensitive populations—women of childbearing age and children—rather than ban the fish, which is the FDA approach. Speaking personally, Brown says federal efforts to discuss science are "nice," but states would be helped more if federal agencies lent a hand in obtaining consistent sampling data from state waters.
"Fish data are different for each state, and state methodology varies. We need help in instituting a sampling system that provides comparable samples. Also, there are a whole lot of lakes that have not been sampled," Brown says. Leading to the Northeast regional study, Brown says, was a Maine survey that found mercury in fish from pristine lakes at levels that would ban their sale by FDA. With no nearby industrial sources of mercury, Brown says, "there appeared to be no reason for this level of contamination." About 47% of mercury air deposition in New England comes from regional sources, 30% originates from U.S. sources outside the region, and the rest comes from a global mercury reservoir, Brown estimates. As incinerator regulations go online, Brown predicts, attention will turn to coal-fired utilities, most of which are outside the region and in the Ohio Valley. With the expected deregulation of electrical utilities, the report warns that more competition may lead to greater use of coal-fired powerplants, more mercury emission, more fish advisories, and more pressure for EPA's utility regulations. In the search for solutions, Minnesota is held up as a model for reducing mercury emissions and establishing a system of fish advisories. Between 1990 and 1995, Minnesota cut mercury emissions in the state from 10,000 lb to 4,200 lb, mostly by reducing mercury-containing products heading to a landfill or incinerator as well as by adding better controls to waste incinerators, says Carol Andrews, who runs the mercury contamination reduction program for the Minnesota Pollution Control Agency. Nearly half the state's waste is incinerated, so removing mercury from waste has had a significant effect on air emissions. Much of the remaining reductions, she says, was attributed to a decision by waste incinerator operators to add activated carbon systems that capture mercury in flue gas. Andrews says the state's goal is to stop mercury's use in products—particularly toys, clothing, games, batteries, and dairy manometers, which are pressure gauges for milking machines that may hold as much as 1 lb of mercury. Minnesota also requires special warnings and handling for fluorescent lamps and one manufacturer runs a "take back" program for thermostats that use mercury. Focus now is shifting to coal-fired utilities, Andrews says, but emission reduc-
tions will be more difficult because activated carbon is less effective there. Minnesota also has perhaps the most thorough and complicated fish advisory system in the country, and it has the highest number of water bodies listed with advisories, some 750. "We have the highest number of advisories because we survey the highest number of lakes," says Patricia McCann, a research scientist in the state's Department of Health. "Our advisories are complicated but we feel people want this information. They want it to make better choices." The state provides information for two general consumer categories: adults, and children and women in child-bearing years. Fish consumption patterns are broken into three categories: vacation, seasonal, and annual. It then provides lake and fish species data for mercury and other contaminants. Warnings begin for fish containing as little as 0.16 ppm mercury. Minnesota's fish advisory booklet runs to 90 pages. This year, FDA is reexamining its standards for mercury in seafood, says Bolger, and early next year the agency may propose new ones. FDA also will begin to rely more on advisories than on bans, he says. Bolger says the agency is expected to elevate consideration of nutritional benefits from fish consumption, along with risk from environmental contaminants, when setting a level. "Only looking at risk is an incomplete analysis and only gets to part of the public health story. We have to include nutritional benefits for a total analysis," Bolger says. FDA's analysis may also include comparisons of the health impact of consuming other protein sources, such as chicken or beef, as compared with fish, he says. "We have to try to put the benefits and risks on the same scale. We must do more than write a paragraph saying, 'It's good to eat fish.' This is completely ignored by the consumer and decisionmaker." Both McCann and Bolger emphasize the need to straddle the thin line between confidently protecting the public, but not scaring people away from a good protein source or needlessly damaging the powerful seafood and fishing industries. Maintaining such a balance is not always easy. Witness a decision last month by Louisiana state officials to post, after a lengthy review, a mercury fishing advisory for choupique caught in the Blind River. The announcement came four days after the annual choupique "fishing rodeo" and fry.^ MAY 11, 1998 C&EN 23
