Turning Amalgam Green

Oct. 1, 1995
Environmentalists monitor the uneasy passage of dentistry`s metal through the waste system, and they want you to help keep amalgam out of it.

Environmentalists monitor the uneasy passage of dentistry`s metal through the waste system, and they want you to help keep amalgam out of it.

Cathleen Terhune Alty, RDH

Dental office wastes in the sewer system include amalgam, X-ray processing chemicals, disinfectants, blood, and chemiclave solution. Check with your local waste water facility to learn the proper disposal methods for these substances. If in doubt, don`t throw it in the garbage or down the drain!

"It`s not easy being green." The Muppets` Kermit the Frog may have been the first to sing it, but the song today includes the chorus heard from the environmentally conscious. It`s not always easy, or inexpensive, to adhere to the green movement`s slogan of reduce, reuse, and recycle - especially in the dental office. With the Occupational Safety and Health Administration`s mandates on infection control, the increase of disposable products in the dental practice has made it even more difficult to adhere to the "three Rs."

However, there are ways to prevent your dental office from compromising the environment, particularly when it comes to metals waste. Although this discussion focuses on amalgam scrap, other metals used in the practice such as the lead foil in X-ray packets can also be recycled.

As most dental staff members know, amalgam scrap is generated when removing existing amalgam restorations and when placing new ones. The scrap is usually aspirated by the suction system, although unused, excess amalgam could also be found on the instrument tray. Larger pieces of aspirated amalgam scrap are caught in the suction system traps, while smaller pieces pass through and exit through the office`s waste water system.

Most office personnel do not give this amalgam another thought. But this amalgam scrap in waste water is currently under scrutiny by many municipalities. Dental offices have become very visible targets because many patients are aware that amalgam filling material contains a small amount of mercury. Some cities are even sending letters to dentists asking questions about their metals waste handling practices. To better understand the cities` concerns, it helps to understand a little about the waste water system and how it operates.

Cleaning out the metals

In most practices, waste water flows out of the dental office, into the city sewer and into the waste water treatment plant. The plant treats the water by allowing solids to settle out, and then they use various means to clean the water that rises to the top. This cleaned water, or effluent, is released into a river or other large body of water so the water can be used again. Various state environmental agencies permit this cleaned water to be discharged only if the effluent meets rigid standards of cleanliness.

"There are limitations of what can be in the water after treatment, particularly when it comes to metals," David Hill, industrial pretreatment coordinator at the City of Dayton (Ohio) Waste Water Treatment Facility, said. "Mercury is a concern because the Environmental Protection Agency allows only a very small amount to be released, compared to other metals. Any amount going into the waste water system affects what ultimately comes out, and our system is not really designed to remove metals."

High metal concentrations can also kill the beneficial bacteria that are used in waste water treatment.

After waste water processing, most of the metals settle out and end up in the sludge (or biosolids), which is applied to farmlands as fertilizer. Research indicates most metals bind to the biosolids and, when used under conditions set by EPA, do not tend to leech out. Some metals, however, remain in the water and are released in the effluent. Because EPA so closely regulates the metal content, particularly mercury, in the waste water, treatment plant engineers actively work to identify mercury dischargers so regulations are met.

Seattle officials analyze amalgam

A few years ago, dental offices in Seattle, Wash., were identified as a source of mercury in the waste water system and were approached by King County Department of Metropolitan Services (Metro).

"In 1989, we saw some indication of mercury in the effluent. So we looked at who put mercury into the system," Baz Stevens of King County metro, said. "At first, we felt dentists should be held to the same discharge standards as other mercury contributors in the system."

Metro began to monitor amalgam/mercury content of waste water exiting from dental offices and discovered the office discharges ranged from 100 to 1,000 parts per million (ppm) mercury, which was higher than Metro`s discharge limit of 0.2 ppm mercury. Most companies in the Seattle area who discharge waste water with metals content are required to install and maintain a pretreatment system to remove metals before they reached the sewer system because the sewage treatment plant is not equipped to handle metals.

So Metro proposed a rule that would require dental offices who place or remove amalgam to install and maintain an amalgam, designed to be at least 90 percent effective in removing amalgam from the waste water. Based on the estimate that 14 percent of the mercury in the system was coming from dental offices, Metro estimated that this would reduce the amalgam sources of mercury to 1 percent or 2 percent of the total.

"At first, we felt dentists should be held to the same discharge standards as other mercury contributors in the system," says Stevens. According to Metro reports, the rule was not to "cause undue economic hardship but instead minimize the amount of amalgam/mercury entering the sewerage system."

But local dentists, while concerned about the environment, were not convinced that amalgam was the problem. Public hearings were held for dentists to air their opinions. Their questions were varied:

"What are the real environmental effects of amalgam?"

"Is amalgam really equal to mercury in the environment?"

"Who will pay for and monitor this separator system?"

"Will this change make an environmental impact and improve our water quality?"

"If amalgam is safe in the human mouth, why can`t we put it in the garbage?"

For several years, Metro worked with local dentists, representatives of the American Dental Association, and other experts to discover what the problems were and what could be done to remedy them.

This mercury is not `raw`

One of the main issues is that the Environmental Protection Agency testing requirements for mercury does not distinguish between bioavailable or "raw mercury" from mercury in its found form, as it appears to be in dental amalgam. Therefore, mercury discharge levels from dental offices appear to be high even when the mercury is still in the amalgam compound.

Dentists reported that amalgam does not behave like the other types of mercury. The American Dental Association also presented research that amalgam does not dissolve and is not necessarily bio-available to living organisms.

After much deliberation, Metro decided "there is not a significant body of scientific data (from any source) to either support or challenge the belief that amalgam is inert in the general environment."

Although Metro could not determine the environmental fate of amalgam in waste water systems, they determined the EPA limits for metals content in the effluent and biosolids were not exceeded. As long as the agency met its EPA requirements, and mercury levels did not increase, dentists would be exempt from mandatory restrictions.

But Metro also stated, "Lacking substantiation of a problem does not necessarily dismiss an effort to control the input of metals to the sewer system from dental offices."

So Metro asked dentists to voluntarily use vacuum separation systems. Most of these systems are based on sedimentation or gravity technology to allow the smaller metals particles to settle out before exiting in the waste water . Metro also encouraged research of amalgam in waste water systems to continue. This compromise, according to Stevens, "opened the door to proceed amicably."

According to recent Metro bulletins, many dental offices have already installed separation units, and the agency`s hope is that this trend will continue without a formal regulatory requirement.

Many European countries have regulated amalgam in the waste water, and, according to Metro, cities in California, Minnesota, Virginia, and Michigan are designing ways to reduce mercury loadings in their systems from dental amalgam.

Many municipalities in other parts of the country are testing the waste water as it leaves dental practices to get an idea of how much metal is being put into the sewer. OThe variances (between offices) are pretty large,O Hill said. OBut we?re showing the EPA that we are actively tracking down mercury sources that contribute to our system.O

Metropolitan waste water specialists urge dental offices not to strain waste systems by putting metals in the practice?s waste water.

What is the best thing to do with scrap amalgam? OTrap it, box it up and send it to a hazardous waste recycler,O Hill said. Personnel who OrecycleO should note that some materials may be considered hazardous, may have to be disinfected prior to shipping, or may need to have special packaging.

As a final outcome, reclaiming the metals is probably more environmentally safe than burying it in a hazardous waste landfill because the metals are reused.

An EPA-licensed refiner in Freeport, N.Y., recycles scrap amalgam to extract the silver and resell it to jewelers. A spokesperson said, OWe ship it out to have the mercury removed from it, then pull out the silver for recycling. We used to get money for the mercury, but nobody wants it anymore.O

OThrowing amalgam in the trash would probably put it into the ground water either by incinerators or landfill,O Hill said. OI?d personally rather pay more to have it handled environmentally safe instead of it being in the water. If I care about my teeth, I probably care about the environment.O

Cathleen Terhune Alty, RDH, is a contributing editor for RDH and is a member of the Office of Sterilization and Asepsis Procedures Research Foundation.