Dental Amalgams - At issue: mouth mercury

Recently, two people who work at the Madison sewer district put a measured amount of water in their mouths and swished it around for a minute. They ended up with concentrations of mercury that were from two to four times greater than the concentrations in the raw waste, he said.

"They had not been to the dentist recently, but they had amalgam fillings," Schellpfeffer said.

Dane County recycling manager John Reindl, who has done extensive mercury research, noted that the very tiny amount excreted in urine and feces adds up, when 400,000 county residents use the toilet several times a day.

Mercury from fillings also can enter the waste stream from dental offices, when patients spit out that little piece of mercury filling after rinsing and it goes down the drain, or when the dentist takes out an old filling and puts in a new, Reindl said.

"Dental mercury doesn't decompose very rapidly. It will go out to sewage sludge in particles and sludge is typically spread on agricultural land," he added.

The handling of dental amalgam filling is getting a lot more attention lately, courtesy of U.S. Rep. Tammy Baldwin, D-Madison. She has introduced a bill that would limit mercury in everyday life by using grants to encourage recycling by schools and other mercury users, banning the sale of mercury thermometers, and requiring amalgam separating devices in every dental office.

The Wisconsin Dental Association opposes her plan.

"Our association has been very pro-active about mercury in wastewater," said Dr. Dennis Engel, a Mequon dentist who is president of the association.

"In 2002 we came out with a brochure on best management practices on how each dentist should deal with dental waste. Last year we came out with a video that was distributed to every dentist in the state. If those practices are used, we could remove 80 percent of all types of dental waste."

The dental association worked with the state Department of Natural Resources in regard to new permitting requirements for mercury in wastewater and is working with sewer districts to meet the new requirements.

But the association opposes mandated dental amalgam separators in every office, saying they are not necessary if the best management practices are used.

Those practices include collecting any extra filling that is carved off a tooth restoration or removed from a patient's mouth or in extracted teeth. That extra amount is kept in a sealed container. Chairside traps and filters in vacuum systems also collect a good percentage of the amalgam, Engel said.

"We segregate that. We do not throw it in the trash where it would be incinerated. We collect it and give to it licensed recyclers," he said.

"We met with Congresswoman Baldwin and said we would like to work with her in developing recycling centers to make it easier for dentists to recycle dental waste, and in creating some grant opportunities. We agreed to disagree on the mandate. There is no scientific evidence that putting in a separators would improve water quality at all. The sewer districts also do a great job of eliminating the mercury at their end."

The Wisconsin Dental Association and the American Dental Association also stress that dentistry provides less than 1 percent of all mercury released into the environment from human activity.

Wait a minute, says Baldwin, who does not plan to drop the equipment requirement from her legislation.

That 1 percent includes air emissions as well as other wastes, she said, and though coal-burning power plants and chlorine plants send the greatest percentage of mercury into the air, mercury used in everyday products contributes a hefty amount in wastewater and air.

"Dentists are the third largest user of mercury in products in the United States, consuming over 22 percent of the 220 metric tons used in 2001," Baldwin said.

"The WDA wanted to tell me about some of the very positive steps the association is taking on this issue. However, this legislation is being proposed at the national level and not all state dental associations have been as pro-active."

Her bill is a national effort to reduce the presence of mercury in water and landfills, which is why the dental provision is included, Baldwin said.

Dentists would have plenty of opportunity to comment on an EPA rule that would implement the provision, she said.

Baldwin said she would be glad to work with the dental association to improve recycling efforts.

"Right now, depending on where you have a dentistry practice, resources for recycling amalgam vary greatly," she said. "They prefer not to have a mandate, but my goal is to have a comprehensive piece of legislation that deals with how mercury gets into waterways and landfills. We hear a lot about legislation aimed at emissions from smokestacks. But there hasn't been a sufficient review of all the ways mercury gets into our environment."

A recent study by the Association of Metropolitan Sewer Districts at seven major municipal wastewater treatment plans found that dental use was by far the greatest contributor to the mercury load, accounting for 40 percent, according to Baldwin.

Meanwhile, the Milwaukee Metropolitan Sewerage District has required that dentists within the district install amalgam separators by 2008.

"In exchange for that, the district decided to work with us and say there would be no testing of effluent coming from our dental offices," Engel said. "The only requirement will be to have someone come in and see the separator installed and examine a manifest from the licensed recycler."

Randy Case, community mercury reduction coordinator for the DNR, said that amalgam forms a significant part of mercury releases into sanitary sewer systems, "probably the single largest release."

The Wisconsin Dental Association has been very cooperative in working to reduce mercury discharges, he said. "We have a partnership in promoting best practices and installing separators," Case said.

A relatively new DNR rule, NR106, requires municipalities to implement community pollution reduction programs if discharges exceed water quality material.

"So municipalities are collecting effluent results for mercury they can compare with discharge standards. We think most will exceed, and then they will need to minimize mercury," Case said.

That means less mercury will have to be used or it will have to be recycled.

"The limit that needs to be met by industrial and municipal sewer systems is 1.3 nanograms per liter. Municipal systems are typically 5 nanograms per liter, which is low but not low enough to meet the standard," Case said. "They don't have to implement it unless data shows they should. The two-year collection period will end in late 2005 for most. We will start receiving proposed plans in late 2005 or early 2006. Implementation would probably be over the next five to 10 years."

Both the Madison and Milwaukee sewer districts have done good pilot work, according to Case.

Schellpfeffer said that about 1 to 2 ounces of mercury comes to the Madison Metropolitan Sewerage District plant in 330 million pounds (40 million gallons) of wastewater per day.

"It is in the parts per trillion range, so testing is difficult. Mercury is certainly something everybody is concerned about, even in these low concentrations. We are trying to reduce sources whenever we can," Schellpfeffer said.

"We produce roughly 110,000 gallons of biosolids a day, so the 1 to 2 ounces will be in that quantity of biosolids. The wastewater comes in and we treat it. We end up with two side streams. For every 1,000 gallons that come in, 3 gallons go out in biosolids and 997 go out as clean water. The biosolids are concentrated and stabilized in a liquid form. We recycle our biosolids to farmland. The sludge is injected below the surface."

Mercury entering the system comes primarily from humans, he said, in dental amalgam, red and yellow food dyes, and old mercury thermometers. For the most part, it comes from homes, though dental offices are another significant source, he said.

Newer dental offices are putting in amalgam separators, according to Schellpfeffer. The Madison sewer district is holding off on an ordinance requiring them, waiting to find out if the state will regulate more broadly.

"We suspect that will happen," Schellpfeffer said. "We are apprising dentists that this is something that is coming and they should be aware."

However, the Madison sewer district is well below limits. "Mercury in our biosolids is 1.9 milligrams per kilogram of solids. The EPA has a limit of 17 for exceptional quality of biosolids. They don't regulate until it is 57 milligrams per kilogram," he said.

Industries have cleaned up their use of mercury and other heavy metals in the last 20 years, according to Schellpfeffer. "The main areas we are looking at, the bulk is from domestic wastewater. The best way to eliminate that is some kind of product substitution somewhere up the consumption line."

Ultimately the solution is to stop using mercury in products, Reindl said.

"We have alternatives for most products. We don't have great alternatives for fluorescent lamps and dental fillings. There are ceramic and gold fillings but some don't think they are very durable. They are also very expensive, and some dental insurance won't cover anything but mercury," he said.

Some nations want to ban mercury in all products, and some want to bury it forever, Reindl said.

"In the United States, we have had legislation to set up a commission to retire mercury," he said. "I suspect we will see a commission formed in the next five years."

E-mail: aweier@madison.com

see also:
How Mercury Causes Brain Neuron Degeneration, University of Calgary, Faculty of Medicine