How dental mercury seeps into the environment
The U.S. Environmental Protection Agency has adopted a rule to require dentists, whose treatment of tooth decay with mercury compounds has sent the toxic substance into public sewers for decades, to contain their discharges by early 2020.
On Friday, the day after EPA Administrator Gina McCarthy signed the final rule, European authorities approved a draft rule that would bar dentists from using mercury compounds to fill cavities in vulnerable populations.
The actions to shield the public from dentists’ use of mercury moved governments on both sides of the Atlantic toward aligning with the goals of a 2013 treaty signed by 128 countries – the Minamata Convention. The treaty, ratified by the United States and 34 other nations, calls for phasing out products that emit mercury vapor and disposing of the toxin more safely.
However, the U.S. Food and Drug administration has yet to curb dentists’ use of mercury compounds, considered the most durable treatment for decayed teeth.
Dentists’ discharges of mercury have resulted in the release of hundreds of tons of the substance into the environment over the past several decades.
The EPA rule, culminating a regulatory battle that began more than a decade ago, is expected to lead the tens of thousands of U.S. dental offices that handle the toxin to install “separators” to catch tiny pieces of mercury-tainted waste. It also requires them to adopt best practices for disposing of the substance, the agency said. It estimated that compliance will capture more than 99 percent of the waste mercury from implants of compounds and from drilling to remove older mercury fillings.
However, the rule does not direct water treatment plants to inspect dental offices to enforce compliance, as environmental activists had sought.
It will take effect 30 days after its formal publication, which is expected shortly, with compliance required within three years.
The EPA estimated that even though about half of dentists have abandoned use of mercury fillings, the new requirement will prevent an estimated 5.1 tons of mercury from flowing each year into public sewer lines. Most dentists are routinely called on to drill out old mercury fillings, which are present in more than 180 million Americans’ teeth, according to one estimate.
McCarthy’s decision resolved a long-running lobbying struggle pitting environmentalists against the American Dental Association and a trade association representing local wastewater treatment utilities, which argued it would be too burdensome for them to enforce the rule, given the number of dental offices.
Dental offices are “the largest source of mercury in municipal wastewater, the largest consumer use and also the largest reservoir of mercury in use today,” said Michael Bender, director of the Vermont-based Mercury Policy Project. He called the separators, which the EPA estimates will cost dentists about $800 per year to operate, “a practical, affordable and available technology for capturing mercury.”
Scientific research has long shown mercury to be one of Earth’s nastiest toxins. Once inhaled in even minute amounts, it moves to the bloodstream and can accumulate in the kidneys, liver and brain, where it damages the central nervous system. It has been linked to memory loss, nerve damage, autoimmune diseases, vision problems, kidney failure, depression, autism and foggy thinking. More recent research suggests it may contribute to Alzheimer’s disease. It also can be lethal.
If elemental mercury combines with certain bacteria, it forms highly toxic methylmercury, which can enter the food chain through fish. The Minamata convention was so named for a disaster in the 1950s in Japan. Mercury-laden wastewater from a chemical plant contaminated fish in Minamata Bay, leading to the deaths of more than 1,700 people who consumed the poisoned fish.
The EPA estimated that dental offices account for about half the mercury in public waste streams. Catching the mercury at its source is crucial, because it’s a naturally occurring element and cannot be destroyed.
In the closing days of George W. Bush’s presidency, the EPA accepted the American Dental Association’s assertion that dentists should be allowed time to voluntarily meet “best practices” that the association had adopted for containing mercury waste.
EPA officials in the Obama administration soon concluded that voluntary measures weren’t working. A dozen states and 18 cities acted on their own, requiring dental offices to install mercury separators.
American Dental Association President Gary Roberts called the new federal rule “a fair and reasonable approach” that is “preferable to a patchwork of rules and regulations across various states and localities.”
Despite mounting evidence of the health risks of mercury fillings, the dental association has continued to vouch that the fillings are safe, asserting that the low-level vapors released when people chew or grind their teeth are not dangerous.
Early this year, McClatchy reported that researchers at the University of Washington had found that low-level releases from mercury fillings present long-term risks of brain damage for people with certain genetic variants – variants found in up to 40 percent of the population.
McClatchy reported last year that the FDA had proposed for the first time that dentists be banned from using mercury compounds, known as amalgam, to fill cavities in pregnant women, nursing mothers, children under 6 and people with mercury allergies, kidney diseases or neurological problems. The agency proposal also called on dentists to avoid using fillings that contain mercury compounds, where possible.
However, officials at the Department of Health and Human Services killed the proposal after a cost-benefit analysis, concluding that the extra cost of alternatives might dissuade low-income people from seeking dental care.
European regulators have moved more aggressively to curb dentists’ use of mercury. On Friday, a committee representing the Council of the European Union endorsed a draft regulation to conform to the Minamata Convention that will be circulated to more than two dozen countries for ratification.
It would impose a ban, effective July 1, 2018, on the use of mercury fillings in primary teeth, children under 15 and pregnant or breastfeeding women unless a specific medical need is cited. The commission said it would report by June 30, 2020, on the feasibility of a total phase-out of mercury use by dentists, “preferably by 2030.”
“Mercury pollution is found all around the globe, even in virgin lands very remote from pollution sources,” said Laszlo Solymos, the Slovak environment minister, who is president of the council. “This proves how dangerous and global this pollution is.”
CORRECTION: An earlier version of this article gave the wrong figure for the amount of mercury disposed into municipal waste streams by dentists each year. It’s 5.1 tons.