DULUTH — Ashes to ashes, dust to dust, dental fillings to mercury emissions.

As Minnesotans increasingly choose cremation, mercury pollution from the practice has risen, too, even as mercury emissions from other industries have fallen dramatically.

While Minnesota’s total mercury emissions dropped by 60% from 2005 to 2022, mercury emissions from cremation almost 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% of the state’s more than 51,100 deceased were cremated in 2022, up more than 6 percentage points in four years.

When dental amalgam — a tooth filling made up of elemental mercury, silver, copper, tin and zinc — is exposed to extremely high cremation temperatures, the mercury volatilizes and enters the atmosphere as vapor. It can then return to earth, converting to toxic methylmercury as it enters the food chain.

“You’re gonna have pretty close to 100% release of mercury from fillings through the stack into the atmosphere,” said John Gilkeson, principal planner at the Minnesota Pollution Control Agency.

(Gary Meader / Duluth Media Group)

Lack of regulations

In 2022, mercury emissions from cremation made up nearly 11.3% of the state’s mercury emissions.

The state has made massive reductions in mercury emissions, namely from coal-fired power plants and even from the wastewater of dentist offices that perform dental amalgam, but the state is not on pace to meet a goal of reducing cremation emissions to 32 pounds of mercury by next year, a goal set in the MCPA’s 2009 statewide mercury total maximum daily load implementation plan.

The state’s overall goal of 789 pounds of mercury emissions per year across all sectors will also be missed, largely due to the taconite industry’s resistance to installing mercury-reduction systems.

It’s not that smaller mercury reduction systems for crematoriums don’t exist — it’s the lack of regulations.

According to Gilkeson, who has worked on mercury product issues for more than 30 years, European crematoriums are being retrofitted with emission-reducing systems, but Minnesota does not require crematoriums to reduce mercury emissions.

“We do not have any regulations here — through our air quality rules or through health department rules — to address these emissions,” he said. “So there’s no drivers, I guess, to install the equipment.”

It’s also expensive.

The University of Minnesota School of Dentistry studied the issue a decade ago and determined scrubbers “are too costly for the majority of small crematoria, which perform low numbers of cremations.”

Hassan Bouchareb, an engineer in the MPCA’s air policy group, said Minnesota’s lack of regulations around mercury from cremation is not unique.

“As far as we know, there’s nothing like that in the United States,” he said.

But there have been attempts at preventing mercury from entering an incinerator in the first place.

From at least 2005 to 2007, bills introduced at the Minnesota Legislature would have required the removal of fillings from corpses before cremation, but the bills never became law.

The U of M School of Dentistry described pre-cremation tooth extraction as “problematic” because rigor mortis — the stiffening of a body after death — and embalming restrict access to the back teeth. Ceramic crowns may also cover the fillings, while dental records and X-rays may not be available before cremation, the school said.

Gary Meader / Duluth Media Group)

Demographic decrease

In 2014, the MPCA and University of Minnesota estimated that a cohort of Minnesotans ages 63-79 had, on average, 2.3 grams of mercury in fillings. But that decreases 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 the Wisconsin-based health care software company Epic, which found less than 6% of dental fillings of back teeth in 2022 were made of amalgam, down from 21% in 2017. Resin and composite fillings make up an increasing share of dental fillings.

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Bouchareb said even if cremations continue to increase, their mercury emissions will eventually decrease.

“People take better care of their teeth,” he said. “There’s 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 generally speaking, (the) Silent Generation and baby boomers are likely to die before their crowns and fillings are replaced with porcelain implants,” she said in an email to the News Tribune. “Younger generations will not have mercury amalgam in their mouths at all.”

Kemmis proposed replacing amalgam with other mercury-free materials.

“A solution within our control is to replace silver fillings and crowns with porcelain,” she said.

But in October 2022, the ADA’s House of Delegates adopted a policy that said advocating the removal of amalgam for the sole purpose of replacing it with a material that doesn’t have mercury is “unwarranted” and violates the organization’s code of ethics and principles of professional conduct.

The policy suggests clinicians should “review the risks and benefits of all restorative options with their patients, and that dental amalgam restorations continue to be used when appropriate for patient care.”

While the ADA maintains the material is safe for patients, it supports a phase-out of dental amalgam.

Mercury in the environment

Nathan Johnson, a professor at the University of Minnesota Duluth’s civil engineering department who studies how mercury moves and transforms through waterbodies and wetlands, said some 90% of 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 on Minnesota, some of it is from Minnesota … but it comes from other parts of the country or the world as well.”

After it falls as inorganic mercury, bacteria can convert it into the toxic form methylmercury.

The Northland’s wetlands are ripe for that transformation.

“Those are the places that are the most efficient at producing methylmercury from inorganic mercury,” Johnson said. “So watersheds or waterbodies that have a lot of wetlands or a lot of goopy sediment at the bottom of the lake, that’s where the conversion to the bio-accumulative form happens.”

It builds up in fish and then anything that eats the fish. That’s the main way it reaches people, Johnson said.

For fetuses, infants and children, the U.S. 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 U.S. Environmental Protection Agency’s reference dose for methylmercury.

Johnson said emissions and mercury concentrations in the atmosphere have been declining, but it will take time for the amount accumulated on the landscape to either wash away or be buried.

Research is also trying to determine the effect of climate and land-use changes on the efficiency of converting inorganic mercury to methylmercury.

“Eventually, the source reductions will become realized as lower mercury everywhere,” Johnson said. “But until that happens, the rate of mercury accumulation may depend largely on this conversion rate, not necessarily the sources.”

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