San Mateo County Dental Society (CA)

San Mateo County Dental Amalgam Management 


Dental Amalgam Management Program (DAMP) data for San Mateo County given to the Water Board in November 2009 is posted below for member  reference. Briefly, by the end of 2009, all wastewater treatment plants in this county have collaborated on consistent requirements for dental amalgam management (except for ocean dischargers). In January 2010, all wastewater treatment plants (non-ocean dischargers) also met with dental office inspectors from San Mateo County Environmental Health Services.




22% or 98 out of 439 amalgam-using dentists had amalgam separators as of November 2009. Wastewater treatment plants are implementing the regional requirements set by the SF Water Board to have 85% of all dentists in a dental amalgam management program by the end of 2012. Widespread installation of amalgam separators is one expected outcome of the program.

Best management practices (BMPs) for dental amalgam were also surveyed. One important BMP is to avoid bleach-containing vacuum cleansers. Bleach can make the mercury more soluble and thereby increase the amount of mercury in the water which can bypass even a separator. Of those dentists surveyed, 77% adhere to this BMP. Regarding the BMP which says dentists “Do not discard scrap amalgam into the sewer,” 66% agreed they adhered to it, leaving room for improvement regarding both of these practices. Wastewater treatment plant inspectors will be continuing outreach until all dentists have been visited and/or inspected.

Amalgam Waste BMPs


Questions or comments, contact:

 Norm Domingo

 Pollution Prevention Specialist

 SBSA (South Bayside System Authority)



Dental Amalgam FAQs

Dental amalgam contains mercury. Mercury in certain forms can be toxic. Doesn’t the use of dental amalgam lead to toxic effects?

No. Not all forms of mercury are the same. Dental amalgam is a durable alloy of silver, copper, tin, zinc, and mercury. The elemental mercury found in dental amalgam is inorganic, in contrast to organic forms such as methyl mercury, found largely in fish and seafood, and thimerosal, an ethyl mercury-based preservative found in pharmaceuticals. It is methyl mercury that is found in our food supply and is a cause for concern. Dental amalgam is a stable alloy that has been studied extensively and has an established record of safety and effectiveness.

If dental amalgam is classified as a hazardous material, how can it be safe when it is in the mouth?

“Hazardous,” in this context, is a regulatory classification that dictates appropriate handling procedures. It does not correctly characterize amalgam’s usefulness or safety as a medical device, or its actual environmental effects. Other devices, such as batteries, mercury-containing lamps, computer and television monitors, are common, widely used devices, and are considered hazardous once they are no longer in use. The “hazardous” label ensures such devices are properly disposed or recycled.

Does dental amalgam release mercury vapor in the body?

Amalgam fillings are known to emit minute quantities of mercury vapor during vigorous chewing or grinding. The amounts of mercury vapor emitted by amalgams fall well within levels considered safe, that is, they show no toxicity and cause no adverse health reactions.

Why has dental amalgam become a wastewater issue?

An estimated 0.4 tons of mercury from dental facilities annually enter surface waters in the U.S. via Publically Owned Treatment Works (POTW) effluents, sewage and sludge incinerator emissions. Chair side traps and vacuum systems capture 78% of amalgam waste from dental offices; amalgam separators increase the amount of amalgam particulate captured to about 97%.

 The California Dental Association has policy recommending that all dentists install amalgam separators to ensure that the amount of mercury entering the water supply from dental fillings is reduced to extremely low levels. Amalgam captured in dental offices via traps and amalgam separators can be recycled instead of incinerated as a biosolid, which reduces the amount of mercury emitted into the air and subsequently into surface water.

Does amalgam that enters the wastewater system convert to the more toxic form of methyl mercury?

Mercury in dental amalgam is highly bound. Studies conducted by Kunkel et al. in 1996 and Okabe et al. in 2003, among others, indicate that mercury remains in the form of amalgam throughout the wastewater conveyance and treatment process. Kunkel et al. studied the potential release of mercury from amalgam in aerobic and anaerobic wastewater treatment systems and did not detect soluble mercury, even when amalgam particles were introduced into the systems at concentrations on the order of 1,000 times the expected concentration of POTW influents.”

Now that tooth colored fillings are widely in use, can’t dentists just use those materials instead of amalgam?

Other materials are effectively used for dental fillings, however, they can not completely replace amalgam. There are situations where tooth colored materials, which must be bonded, are difficult to use and where amalgam is the optimal restorative material. The dental material fact sheet, required by the California Dental Board to be distributed to patients, was developed to inform patients of the benefits and risks of each restorative material. The choice to use amalgam, which is a safe and effective filling material, should remain an informed choice that is made by the dentist in consultation with each individual patient. CDA/2010 For additional information, contact Alicia Malaby, CDA Communications Director, at 800.232.7645 x5372