DULUTH — Ashes to ashes, dust to dust, dental fillings to mercury emissions.
As Minnesotans increasingly choose incineration, mercury pollution from the practice has also increased, even as mercury emissions from other industries have dropped dramatically.
While Minnesota’s total mercury emissions fell 60 percent from 2005 to 2022, mercury emissions from incineration nearly doubled — from 80 pounds in 2005 to 149.6 pounds in 2022, according to the Minnesota Pollution Control Agency.
According to the Cremation Association of North America, 72.7 percent of the state’s more than 51,100 deceased were cremated in 2022, an increase of more than 6 percentage points in four years.
When dental amalgam – a tooth filling made of elemental mercury, silver, copper, tin and zinc – is exposed to extremely high combustion temperatures, the mercury volatilizes and enters the atmosphere as vapor. It can then return to the earth, turning into toxic methylmercury as it enters the food chain.
“You’re going to have almost 100 percent release of mercury from the fills through the stack into the atmosphere,” said John Gilkeson, principal planner at the Minnesota Pollution Control Agency.
Lack of regulations
In 2022, mercury emissions from incineration accounted for nearly 11.3% of the state’s mercury emissions.
The state has made huge reductions in mercury emissions, specifically from coal-fired power plants and even from wastewater from dental practices that perform dental amalgam, but the state is not on pace to meet its goal of reducing incineration emissions to 32 lbs. of mercury by next year, a goal set in the MCPA’s 2009 Total Maximum Daily Mercury Load Implementation Plan.
The state’s overall goal of 789 pounds of mercury emissions per year across all sectors would also be missed, largely because of the taconite industry’s resistance to installing mercury abatement systems.
It’s not that there aren’t smaller mercury reduction systems for crematoria — it’s the lack of regulations.
According to Gilkeson, who has worked on mercury products for more than 30 years, European crematoria are retrofitted with emission reduction systems, but Minnesota does not require crematoria to reduce mercury emissions.
“We don’t have any regulation here — through our air quality rules or through the health department rules — to deal with these emissions,” he said. “So no drivers, I guess, to install the hardware.”
It is also expensive.
The University of Minnesota School of Dentistry studied the issue a decade ago and found that scrubbers “are prohibitively expensive for the majority of small, low-cremation crematoria.”
Hassan Bouchareb, an engineer with the MPCA’s aviation policy team, said Minnesota’s lack of regulations on mercury from incineration is not unique.
“As far as we know, there’s nothing like this in the United States,” he said.
But efforts have been made to prevent mercury from entering an incinerator in the first place.
From at least 2005 to 2007, bills introduced in the Minnesota legislature would have required fillings to be removed from corpses before cremation, but the bills never became law.
The U of M School of Dentistry described extracting teeth before cremation as “problematic” because rigor — the rigidity of a body after death — and embalming limit access to back teeth. Ceramic crowns may also cover fillings, and dental records and X-rays may not be available prior to cremation, the school said.
Population decline
In 2014, the MPCA and the University of Minnesota estimated that a group of Minnesotans ages 63-79 had, on average, 2.3 grams of mercury in fillings. But that diminishes with subsequent generations, Bouchareb said.
In response to the News Tribune’s request for comment, the American Dental Association, or ADA, pointed to a 2023 study by Epic Research, an arm of Wisconsin-based healthcare software company Epic, that found less than 6 percent of of dental fillings Back teeth in 2022 were made of amalgam, up from 21% in 2017. Resin fillings and composites make up a growing share of dental fillings.
Bouchareb said that even if incinerators continue to increase, their mercury emissions will eventually decrease.
“People are taking better care of their teeth,” he said. “There is less mercury used in dental applications.”
That’s how Barbara Kemmis, executive director of the Cremation Association of North America, sees it.
“This is a demographic issue, as in general, the Silent Generation and baby boomers are likely to die before their crowns and fillings are replaced with porcelain implants,” he said in an email to the News Tribune. “Younger generations won’t have mercury amalgam in their mouths at all.”
Kemmis suggested replacing amalgam with other mercury-free materials.
“One solution to our control is to replace silver fillings and porcelain crowns,” he said.
However, in October 2022, the ADA House of Delegates adopted a policy saying that advocating the removal of amalgam for the sole purpose of replacing it with a mercury-free material is “unwarranted” and violates the code of ethics and principles of the organism. professional behavior.
The policy suggests that clinicians “review the risks and benefits of all restorative options with their patients and that dental amalgam restorations will continue to be used when appropriate for patient care.”
While the ADA maintains that the material is safe for patients, it advocates phasing out dental amalgam.
Mercury in the environment
Nathan Johnson, a professor in the University of Minnesota Duluth’s civil engineering department who studies how mercury moves and transforms through water bodies and wetlands, said about 90 percent of the mercury in the state comes from elsewhere.
“It’s more of a global pollutant than a regional pollutant,” he said. “Mercury just spends a long time in the atmosphere. So a lot of the mercury that ends up in the precipitation that falls in Minnesota, some of it is from Minnesota … but it also comes from other parts of the country or the world.”
After falling as inorganic mercury, bacteria can convert it to the toxic form methylmercury.
Northland wetlands are ripe for this transformation.
“These are the places that are most efficient at producing methylmercury from inorganic mercury,” Johnson said. “So watersheds or bodies of water that have a lot of wetlands or a lot of dirty lake bottom sediments, that’s where the conversion to the bioaccumulative form happens.”
It accumulates in the fish and then in everything the fish eats. That’s the main way he reaches people, Johnson said.
For fetuses, infants and children, the US Environmental Protection Agency says the primary health effect of methylmercury is impaired neurological development.
In 2011, the Minnesota Department of Health found that 10% of Minnesota infants born in the Lake Superior basin had mercury levels above the US Environmental Protection Agency’s reference dose for methylmercury.
Johnson said emissions and concentrations of mercury in the atmosphere are declining, but it will take time for the amount that has accumulated in the landscape to be washed away or buried.
The research is also trying to determine the effect of climate change and land use on the efficiency of converting inorganic mercury to methylmercury.
“Ultimately, source reductions will be seen as lower mercury everywhere,” Johnson said. “But until that happens, the rate of mercury accumulation may depend largely on this conversion rate, not necessarily on the sources.”
