Mercury in the news
April 22nd, 2010
New studies on mercury in US fish
Gold mining without mercury
Canadian residents demand action on mercury in water
Effects of very low levels of methylmercury on Arctic mamals
Studies Aim to Resolve Confusion Over Mercury Risks From Fish US News April 21 2010 LA Times April 22 2010
Jacob Lowenstein of Columbia University and his colleagues, found that not all tuna species have the same mercury content, and that not all parts of the fish have equal mercury content. “We found that mercury levels are linked to specific species,” says Lowenstein. “So far, the U.S. does not require restaurants and merchants to clarify what species they are selling or trading, but species names and clearer labeling would allow consumers to exercise greater control over the level of mercury they imbibe.”
One hundred samples of sushi tuna were taken over a two-year period from 54 restaurants and 15 supermarkets in New York, New Jersey and Colorado and analyzed for mercury content. Overall, researchers found concentrations of mercury lower in supermarket samples than restaurant samples. Higher mercury concentrations were found in bluefin akami tuna and all bigeye tuna samples than in bluefin toro (fatty tuna) and yellowfin. Supermarket sushi and sashimi usually feature yellowfin tuna. Owing to the high mercury contamination in some of the sushi samples, Lowenstein’s group concludes that “[government] health agencies should consider adding bigeye and bluefin tuna to mercury advisories” — fish to be avoided by especially vulnerable groups, such as pregnant and nursing women or young children. [Lowenstein et al (2010) Biology Letters DNA barcodes reveal species-specific mercury levels in tuna sushi that pose a health risk to consumers]
Shawn Gerstenberger and his colleagues at the University of Nevada Las Vegas took on the more prosaic form of this fish: canned tuna. The toxicologist and his team initially bought 155 cans of solid-white, chunk-white and chunk-light tuna. All came from three of the most popular US national brands. The white consists of albacore only; light is mostly skipjack tuna. In the February Environmental Toxicology and Chemistry, they report finding that average mercury concentrations in all three brands of tuna exceeded EPA’s 0.5 ppm advisory, and the average for one brand was more than 0.7 ppm. Depending on the brand, 4 to 7 percent of the tuna surpassed even FDA’s action level.
Canned tuna is a low-cost, low-fat source of protein. Indeed, it’s subsidized as a good source of nutrition by the federal Women, Infants and Children program. However, because of his team’s new data, Gerstenberger argues that “stricter regulation of the mercury in canned tuna is necessary.” At 0.5 ppm mercury in canned tuna, a 25-kilogram (55-pound) child can safely eat only one serving every two weeks, his team calculates. Increase that contamination to 0.77 ppm mercury, the average for one of the brands his group tested, and the same child should not eat a serving of tuna more than once every three weeks and two days, they calculate. Gerstenberger would like to see FDA and EPA develop a clear, consistent policy on how much mercury can be eaten safely. [Gerstenberger et al (2010) An evaluation of mercury concentrations in three brands of canned tuna]
New studies have shown that over a third of mercury in the US diet comes from tuna, and that not all tuna are equal in mercury content. A study by Edward Groth in the journal Environmental Research analysed the US consumption of seafood and the mercury levels of each species to reveal that 37.4% of the US’s mercury consumption is from tuna. Groth, a New York City–based consultant, pored over FDA’s database for mercury contamination in 51 different varieties of fish and found a 100-fold difference from the least contaminated (shrimp, tilapia and clams) to the most tainted (tilefish from the Gulf of Mexico). Groth reviews relative mercury concentrations by fish type and then groups popular ones by mercury level into a chart that can fit into a wallet. Despite mercury’s lingering presence, Groth maintains, “everybody should eat fish — more than most now eat.” Yet until now, he says, “consumers haven’t had the information they need to make smart decisions.” But emerging data are identifying some lower contaminated species, he says, and by focusing on them, most consumers should be able to avoid harmful exposures. Link to mercury in fish chart [Groth (2010) Ranking the contributions of commercial fish and shellfish varieties to mercury exposure in the United States: Implications for risk communication.]
Peruvian eyes “green gold” to end mercury dumping Reuters April 21 2010
A Peruvian engineer, Carlos Villachica, says he has come up with an environmentally sound way to isolate gold from clumps of sand without using toxic mercury that wildcat miners in the Amazon basin rely on to extract the precious metal, then dump into rivers. The machine would produce up to 95 percent of the gold obtained by using mercury by wildcat miners, who often put their own health at risk by exposing themselves to the toxic metal. Peru is the world’s No. 6 producer of the precious metal and shipments of gold and other metals make up 60 percent of its exports. Patrick Taylor and Corby Anderson, two colleagues at the Colorado School of Mines, said it remains to be seen what the invention is capable of doing. “He might be reaping some gold, but we would need to see the results. He’s not going to produce pure gold, just a concentrate,” Anderson said. But, Taylor said, there is room for testing new technologies.
Grassy Narrows residents demand provincial action on mercury in the water. CBC news April 7 2010
The environmental group Earthroots released a study Tuesday supporting the reserve’s argument that mercury problems persist. A Dryden, Ont., paper mill dumped the equivalent of 9,000 kilograms of mercury into the Wabigoon River between 1962 and 1970, causing long-term health problems for more than 100 people in the community, Earthroots said.
Dr. Masazumi Harada, a Japanese mercury expert involved in the Earthroots study, first visited Grassy Narrows in 1975. He found some residents with mercury levels over three times the Health Canada limit. Harada visited again several years ago and found 43 per cent of the people who had mercury levels above Health Canada guidelines in 1975 had died. Even residents whose mercury levels were within the limits set by Health Canada were still experiencing mercury-related problems, Harada found.
Under a 1985 compensation deal, those with mercury poisoning recognized by the board received $250 to $800 a month. The protesters, however, demanded that governments acknowledge that mercury poisoning is still a problem. They want the federal government to re-examine and tighten guidelines covering cumulative exposure to low levels of mercury. They also want the government to permanently monitor mercury levels through an environmental centre in the community. Ottawa stopped monitoring mercury levels in the area in 1999, claiming that the levels of mercury in the Wabigoon River are below federal guidelines. Mercury has caused more than health problems for Grassy River. Fishing was banned from the river in 1970 after the river was contaminated. This caused an immediate jump in local unemployment — to 80 per cent — a level that has persisted ever since.
Grisly research in the Arctic is calling into question what we think we know about mercury’s toxic effects: Against the Element – The Scientist (2010-04-01) Link to full article and video
A research project by University of Northern British Columbia and the Nunavik Research Centre in Kuujjuaq, Northern Quebec is looking at polar bear brains to investigate neurochemical changes associated with low levels of exposure to the toxic metal mercury. Environmental health researcher Laurie Chan’s group is making biochemical measurements of brain receptors and enzymes to study the close links between neuronal cell death and mercury uptake, and his team is producing some surprising—and unsettling—findings. “We see subtle changes in the brain before the onset of clinical outcomes,” says Chan.
In short, he and others are seeing biochemical changes in the brains of polar bears, mink, wild river otters, and other species. These biochemical changes could translate into physiological changes—such as defects in memory, language, attention, motor function and visual-spatial abilities—that often go unnoticed until it’s too late and the animal has suffered significant damage from mercury.
Given the neurotoxicity observed in wildlife, “we have to wonder if the same thing happens in humans—and it probably does,” says Niladri Basu, a former grad student of Chan, now at the University of Michigan, Ann Arbor. “The problem is that we can’t go into humans and get their brains.” Ideally, a single animal would near-perfectly mimic the pathology seen in humans to serve as a proxy. But because the species-level diversity in the quantities of mercury toxicity is so great, none of the mammals that Chan, Basu or others have looked at is emerging as good stand-in models for deciphering mercury’s toll on human populations at risk. “Unfortunately,” says Chan, “the fact that we’re seeing more and more differences between species means it’s less and less likely that it’ll be feasible to use the results we see in wildlife to extrapolate to humans.” To investigate Chan has been searching for peripheral neurochemical biomarkers in blood.
