1 Milwaukee Journal Sentinel Posted Online: February 9, 2008 

## Dentists filtering out mercury But nearly one-fifth miss MMSD deadline

By DON BEHM dbehm@journalsentinel.com Dentists throughout Wisconsin are being told they must end routine flushing of mercury to sewage treatment plants, where the toxi c metal is released to the environment. Removing silver-colored fillings from patients' mouths, and placing new silver fillings in, are ongoing and significant s ources of mercury to sewe rs, say federal and state environmental regulators. They are curtailing di scharges of the metal as part of a strategy to reduce both contamination of fish in lakes and rivers, and th e risk of ill health effects to the people who eat those fish. Unless there is a large industrial source in a community, about 50% of the mercury in wastewater flowing to sewage treatment plan ts comes from dental offices using silver amalgam, said Randy Case, community merc ury reduction coordinator with the state Department of Natural Resources. Any Wisconsin sewage treatment plant thatcannot meet stringent mercury discharge limits must implement programs in its community to minimize the volume of the metal flushed to sewers, Case said. The Milwaukee Metropolitan Sewerage District and 25 others in th e state are the first group required to test treated wa stewater for remaining mercury. 

### Mandates for dentists Though treatment plant operators have approached hospitals, medical clinics and schools with voluntary plans to keep mercury out of their drains, MMSD and several other municipal wastewater utilities are mandating us e of special mercury collection devices at dental offices. Silver-colored fillings are formed from an amalgam containing 50% liquid mercury and several other metals: silver, tin, copper and zi nc. Mercury has been used in fillings for more than 150 years because it can be easil y shaped, is inexpensiv e and it adheres to a tooth under wet conditi ons inside a mouth. Mercury vapor is released from amalgam when a filling is formed and when people chew food. No medical studies to date have linked exposure to vapors from amalgam to ill health effects in children or adults, according to the U. S. Food and Drug Administration.2 Use of silver fillings is declining, however, as resin composites and other substitutes become more widely used for repairing cavities in teeth.

Bacteria in lakes and rivers transform elemen tal mercury to a toxic methyl form that can accumulate in fish and damage the health of people who eat the fish. Almost all waste amalgam can be removed fr om a dental office's wastewater through a series of relatively inexpensive steps, sa id Tom Nowicki, a senior industrial waste engineer with MMSD. A trap in the chair-side vacuum line collects large chunks of the all oy drilled out of teeth. And the installation of filters or gravity separators can remove 95% or more of the remaining amalgam in the sludge of water, saliva and other fluids suctioned out of a mouth, Nowicki said. 

### Compliance rate Feb. 1 was the final day for dental offices in the Milwaukee Metropolitan Sewerage District's four-county service ar ea and in the Racine sewerage district to comply with local separator mandates. Though they were notified of the deadline four years ago, nearly one -fifth of 313 dental offices handling mercury amalgam in MMSD's service area had not complied by Friday, Nowicki said.

The district will send a letter to each of the noncompliant dentists, reminding them of the mandate and asking them to comply within th e next 30 days, he said. Nowicki also plans to visit each of the offices that did not install separators in an attempt to bring them into compliance by year's end, he said. MMSD could fo rce dental clinics to install separators under its regulation. The 81% compliance rate was less than exp ected, Mequon dentist Dennis Engel said. He is the former chairman of the Wisconsin Dental Association's amalgam task force. The association has endorsed use of sepa rators to collect waste amalgam. "I'm confident we'll have close to 100% comp liance soon," Engel sai d. "Dentists want to be good environmental stewards. "Some of this might have to do with procras tination in ordering se parators and then not being able to get them installed by the deadline." Among other Wisconsin municipal sewerage districts with 2008 compliance deadlines are: Neenah-Menasha, June 1; Oshkosh, Sept. 30; Grand Chute and Menasha West, Oct. 1; Wausau, Oct. 31; and Madison, Fond du Lac and Green Bay-De Pere, Dec. 31.3 The Green Bay Metropolitan Sewerage Distri ct is offering $500 grants to each of the 100 dental offices in Green Bay and De Pere th at handle mercury amalgam. The grants are intended to help pay costs of purchasing a nd installing separators, said John Kennedy, environmental programs manager for the district. To date, only 30 dental offices have ta ken advantage of the offer, he said. Waukesha, Watertown, Beloit and La Crosse have set 2009 deadlines. Separators cost $600 to $1,500 for dental offices . Marquette University's Dental School paid about $6,000 for the separator serving 163 chairs in its clinic, and $2,000 for a separator at each of its two of f-campus clinics, said Timothy Creamer, a senior associate dean with the school.

Installation can cost an addi tional $200 to $600 or more. Fees for recycling mercury from dental o ffices vary from $300 to $500 a year, depending on the volume. Canisters from separators are simply removed one to two times a year and shipped to a licensed merc ury recycling company.

From the Feb. 10, 2008 editions of the Milwaukee Journal Sentinel