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Dental Clinics and Mercury Fillings

The information provided on this page is focused on reducing the environmental impact from amalgam when used in or removed from patients at a dental clinic.

The largest impact of amalgam waste will be in the wastewater discharged from the clinic. Mercury does not break down; it is a "forever" chemical. Once it makes its way into our water systems from human sources, it is difficult to remove. The Great Lakes target concentration for mercury is 1.3 parts per trillion, which is about the amount of mercury in a single size 2 amalgam capsule (at 500 mg/capsule) in 100 million gallons of water.

A small 10-acre lake is about 16 million gallons, so just 1 capsule released will bring that lake well above safe levels. A lake where local kids go swimming or neighbors might fish from the shore is contaminated with unsafe levels of mercury and exposes everyone who uses that lake or consumes the fish.

Mercury from fillings may also become an air pollutant if disposed of in an incinerator, whether through disposal of extracted teeth with amalgam fillings in medical waste bags, or through sewage sludge collected at a publicly owned treatment works (POTW). This is why teeth containing amalgam are not allowed to be disposed of with infectious waste, and combustion of certain metal bearing hazardous waste (including mercury) is prohibited by hazardous waste rules.

A solid waste exhibits a toxicity characteristic (TC) – making it a hazardous waste – if the extract (obtained using the toxicity characteristic leaching procedure or TCLP) from a representative sample of the waste contains the contaminant at a concentration at or above the regulatory level, which for mercury (D009) is 0.2 mg/L or 200 µg/L.

Amalgam separators sent to a legitimate recycling facility will result in the mercury being extracted and reused in industry, thereby eliminating those sources of pollution as well as the impact of mining of virgin mercury from the environment.

Dental amalgam was historically the largest source of mercury being discharged to treatment plants. In 2017, U.S. Environmental Protection Agency (EPA) wrote specific rules to minimize those discharges from dentist offices. Other EPA rules are in place to address industrial sources of mercury to the environment, such as power plants and incinerators.

Wisconsin DNR incorporated the EPA standards for amalgam collection and recycling in the state administrative code chapter NR 229 in April 2022. Clinics that discharge to a local POTW must work with their municipal utility to comply with their standards, and those POTWs report to DNR on how they are complying with the state rule. Clinics that do not have a local POTW must report directly to DNR on their compliance practices. Clinics that report direct to DNR can use the One Time Compliance Report Form (SB-145).

The main requirements include:

  • install, operate, and maintain an amalgam separator or removal device that meet the criteria in the code
  • follow the best management practices:
    • do not discharge any waste amalgam to the POTW, including from chair-side traps, screens, vacuum pump filters, dental tools, cuspidors, or collection devices
    • do not clean equipment that discharges amalgam waste (dental unit water lines, chair-side traps, vacuum lines) with oxidizing or acidic cleaners, such as bleach, chlorine, iodine, or peroxide, or anything that has a pH lower than 6 or greater than 8

Milwaukee Metropolitan Sewerage District partnered with UW Extension to create a guidebook for dentist offices on handling amalgam and mercury.

Most dental clinics will be Very Small Quantity Generators (VSQG) of hazardous waste. Businesses generating hazardous waste must identify, track and maintain records of hazardous waste generation and accumulation to determine which regulatory requirements apply to their waste management. The generator's first responsibility is to determine if the waste materials being generated are hazardous wastes. Next, determine how much hazardous waste you are generating. If you generate no more than 220 pounds of non-acute hazardous waste and no more than 2.2 pounds of acute hazardous waste per calendar month, your business is a VSQG. The total quantity that a VSQG can store on site at one time is 2,200 lbs. (approximately five, 55-gallon drums) of non-acute hazardous waste.

To determine whether your dental office generates hazardous waste and whether it is a Very Small or Small Quantity Generator, review the Waste Determinations and Recordkeeping (WA-1152) publication and the Quick Reference Guide for Hazardous Waste Generators (WA-1821).

Amalgam waste

Amalgam waste not handled properly is considered hazardous waste. When metal wastes and metal wastewater sludge wastes are properly recycled they can be considered exempt from regulation as a hazardous waste. Special amalgam disposal arrangements have to be made no matter what your hazardous waste generator status. Recycling is always the better option for handling hazardous wastes when available. Work with your amalgam separator vendor to ship amalgam containers and amalgam buckets to a legitimate recycler. Your clinic is responsible for showing that the amalgam waste has been legitimately recycled in order to use the metal recycling exemption.

Medication/pharmaceutical wastes

Medications should be collected and managed properly – never flush them. Flushing hazardous waste pharmaceuticals is prohibited under the hazardous waste rules. Learn more about non-household pharmaceutical waste disposal and review the Table of Common Wastes in Healthcare (WA-1259).

Pharmaceuticals can be hazardous wastes with special disposal requirements as well. The same criteria that make other wastes hazardous, such as ignitability and toxicity, need to be evaluated for your pharmaceutical wastes to determine if they are hazardous waste. Small and large quantity generators that administer or dispense pharmaceuticals are required to notify and operate under Subchapter P for the management of hazardous waste pharmaceuticals. VSQGs are also allowed to opt into Subchapter P to take advantage of these streamlined regulations but are not required to and can continue to manage hazardous waste pharmaceuticals as normal hazardous waste instead. For more information on Subchapter P, review Healthcare Facilities: Pharmaceutical Wastes and Subchapter P (WA-1902).

In some cases, when containers that have been used are considered empty of all hazardous contents, they can be discarded as regular waste or infectious waste rather than through hazardous waste disposal. To understand when commonly used containers such as syringes and IV bags are considered empty of hazardous waste, review Pharmaceutical Waste: Empty Containers (WA-1256).

Other wastes found in dental clinics that can be considered hazardous:

  • Sterilizer and disinfectants: refer to the Safety Data Sheets for each of the chemicals used and see if they meet any of the criteria for being hazardous.
  • Silver fixer, developer and cleaners from x-rays and x-ray film may also be hazardous wastes that should be recycled and not put down the drain or in the trash. If the silver is reclaimed/recycled, this may also fall under the exemption for a metal bearing wastewater sludge.
  • Lead foil that shields x-ray film, protective lead shields and lead aprons are hazardous wastes that should be recycled.
  • Excess inventories of alcohol-based sanitizers may not be disposed of in the regular trash. Check the SDS of the sanitizer to determine ignitability.
  • Amalgam capsules that cannot be emptied (no visible amalgam) should be recycled or handled as hazardous waste. Make sure that the container used to accumulate capsules is well sealed and labeled.
  • Non-contact or scrap amalgam should be recycled or handled as hazardous waste.
  • Extracted teeth containing amalgam should be disinfected. A disinfected tooth with amalgam should not be placed in biohazard containers. Discuss the recycling of disinfected, extracted teeth with amalgam with your amalgam recycler.
  • Amalgam sludge that accumulates in the lower canister of the amalgam separator must be recycled or handled as hazardous waste. When the collection container sediment level reaches the full line, or when the separator has been in service for one year (whichever comes first), the collection container must be replaced per the manufacturer's instructions.
  • Disposable chair-side traps should be accumulated in a container for recycling or treated as hazardous waste.
  • Reusable chair-side traps should be removed from the chair-side unit and emptied into a recycling container. The contents of the traps should not be disposed of in the regular trash. Reusable traps should NOT be rinsed in a sink.
  • Amalgam separator filters that are not recycled should be managed as hazardous waste.
  • Vacuum pump filters or traps should be changed according to the manufacturer’s recommended schedule.
  • Nitrous and Oxygen tanks should be recycled through your gas supplier.
  • Unused and used anesthetic gasses should be recycled through your gas supplier.
  • Anesthetic gas scavenging canisters (used) should be evaluated for hazardous waste characteristics. It should be noted that off gassing of volatile chemicals can occur from scavenging canisters.
  • Aerosol cans that are unusable or cannot be emptied due to a defective or broken spray nozzle may need to be managed as hazardous waste. Refer to WA-1784 for additional guidance.
  • 3-D Printer waste may include spent isopropyl alcohol that is used to clean the printer of excess liquid resin. Spent IPA is an ignitable hazardous waste.
  • X-ray machines manufactured before July 2, 1979, may contain PCB dielectric fluids at varying concentrations in the transformers and capacitors located in the machine.
  • Chemical indicators including tape, indicator strips and sterilization pouches may contain lead or barium. Consult with the manufacturer to ensure that strips do not contain heavy metals.

Dental offices may also generate universal wastes including lamps (fluorescent, compact fluorescent, high intensity discharge, halogen), batteries (rechargeable, lithium, NiCad, mercury, lead-acid), mercury-containing equipment (thermometers, thermostats, barometers, switches) and pesticides.

Refer to the Universal waste webpage for more information.

Dental offices maintain air compressor and vacuum systems that require the management of used oil. Refer to WA-233 for guidelines on managing used oil.

Depending on how you ship your hazardous wastes off site, you may need an EPA ID, which can be obtained online or filed hard copy using EPA Form 8700-12. For assistance with the electronic, hard copy or mailed version of the application or to submit the completed application, contact the DNR regional environmental program associate for your county. Review the publication on Very Small Quantity Generators (WA-295) for more details.

Also, if you are planning a bulk clean out of old, unused clinic wastes that might be hazardous, or if you have a spill that generates more hazardous waste than normal, you can notify DNR of an episodic generation event. For details on how to file that notification, review the publication WA-1872.

For additional resources on health care wastes, review the DNR's Hazardous Waste Management at Healthcare Facilities webpage and the Pollution Prevention and Compliance Information for the Healthcare Industry website.

Who must comply with this rule?

The vast majority of dental facilities that discharge wastewater into a publicly owned treatment works (POTW) (e.g., municipal sewage system) are subject to this rule ("dental dischargers"). However, there are some exceptions. Dental dischargers that do not place dental amalgam, and do not remove dental amalgam except in limited emergency or unplanned, unanticipated circumstances are exempt from any further requirements as long as they certify as such in a one-time compliance report to their Control Authority. Dental dischargers that exclusively practice one or more of the following specialties are not subject to any of the rule’s requirements, including submission of a one-time compliance report to their Control Authority:

  • Oral pathology
  • Oral and maxillofacial radiology
  • Oral and maxillofacial surgery
  • Orthodontics
  • Periodontics
  • Prosthodontics

Additionally, mobile units are not subject to any of the rule's requirements, including submission of a one-time compliance report to their Control Authority. A mobile unit is a specialized mobile self-contained van, trailer, or equipment used in providing dentistry services at multiple locations. Dental facilities that do not discharge their amalgam process wastewater into a POTW are also not subject to any of the rule's requirements, including submission of a one-time compliance report to their Control Authority. For example, dental facilities that discharge amalgam process wastewater into a septic system are not subject to this rule. To determine if the Wisconsin rule applies to your facility, see § NR 229.01, Wis. Adm. Code (Applicability).

What are the basic requirements of the rule?

The requirements for dental dischargers subject to the rule are detailed in the rule. Here, they are summarized as follows:

  • Ensure the removal of dental amalgam solids from all amalgam process wastewater via amalgam separator(s) or equivalent device(s) that meet the standard of the final rule. See § NR 229.03 (1) and (2), Wis. Adm. Code for an existing source and § NR 229.04, Wis. Adm. Code for a new source.
  • Implementation of two best management practices. See § NR 229.03(2), Wis. Adm. Code for an existing source and § NR 229.04, Wis. Adm. Code for a new source.
  • Comply with reporting requirements. See § NR 229.05, Wis. Adm. Code.
  • Maintain and make available for inspection certain records documenting compliance. See § NR 229.05, Wis. Adm. Code
What are the compliance deadlines?

Dental dischargers (under any ownership) that were discharging into POTWs prior to July 14, 2017 ("existing sources"), must be in compliance with the standards by July 14, 2020, and submit a one-time compliance report certifying such by October 12, 2020. Dental dischargers whose first discharge to a POTW occurs after July 14, 2017 ("new sources") must be in compliance with the standards immediately and submit a one-time compliance report certifying such within 90 days after first discharge to a POTW. If the dental discharger transfers ownership, what are the deadlines for a new owner to submit a one-time compliance report? If an "existing source" dental discharger transfers ownership, the new owner must submit a new one-time compliance report to the Control Authority by October 12, 2020, or if the transfer occurs after July 15, 2020, no later than 90 days after the transfer. If a "new source" dental discharger transfers ownership, the new owner must submit a new one-time compliance report to the Control Authority no later than 90 days after the transfer.

Does this rule require standards for the type of amalgam separator I install?

Yes. For an existing source see § § NR 229.03 (1) and (2), Wis. Adm. Code for an existing source and § NR 229.04, Wis. Adm. Code for new sources.

Do I have to replace my existing separator?

It depends. § NR 229.03(1)(a)3, Wis. Adm. Code allows dental dischargers that had installed and were using an amalgam separator prior to June 14, 2017 to continue to use it until June 14, 2027 if it is functioning properly and does not need to be replaced. This is referred to as a "grandfathering" provision or clause. The facility must still file a one-time compliance report certifying such by October 12, 2020. If the amalgam separator meets the standards of the rule, see § NR 229.03 (1), Wis. Adm. Code, the grandfathering provision need not apply. If a dental discharger covered by the grandfather clause transfers ownership, the new owner may continue using the grandfathered separator until June 14, 2027 if it is functioning properly and does not need to be replaced. The new owner must still file the one-time compliance report.

I have a wastewater retaining tank technology that collects all amalgam process wastewater and my dental facility does not discharge any amalgam process wastewater to a POTW. Am I exempt from the Dental Office Category Rule?

Yes. See § NR 229.01(5), Wis. Adm. Code. As long as the dental facility does not discharge any amalgam process wastewater from the tank or otherwise, it is not subject to any of the rule's requirements, including submission of a one-time compliance report to their Control Authority.

My dental facility has a technology that removes amalgam from wastewater as efficiently as an amalgam separator, but it is a different type of device, and therefore does not qualify to meet the ISO standard for amalgam separators. Does this device satisfy the requirements of this rule?

The rule includes a provision at § NR 229.03(1)(b) that allows the performance standard of the rule to be met with the use of an amalgam-removing technology other than an amalgam separator (i.e., equivalent device). EPA included this provision to allow use of amalgam removal devices that are equivalent to amalgam separators in several respects (e.g. the percentage of removal of mass of solids) but that may not fall under the amalgam separator classification. The equivalent device is required to meet the same requirements and removal efficiencies, as specified in § § NR 229.03 (1), Wis. Adm. Code.

Does this rule have recordkeeping requirements for dental dischargers?

Yes. See § NR 229.05, Wis. Adm. Code.

Does this rule have inspection or maintenance requirements for dental dischargers?

Yes. See § § NR 229.03, Wis. Adm. Code.

What information must be in my one-time compliance report?

See § NR 229.05 Wis. Adm. Code. A sample one-time compliance report that includes the information required by the rule may be found elsewhere on this website.

  • Note to dental dischargers: Please contact your Control Authority to ensure that you have obtained the correct form from your Control Authority. In addition, you may be subject to additional reporting requirements in accordance with state and local law.
Where should dental dischargers send their one-time compliance report? Who is my "Control Authority?"

Dentists should obtain and send their one-time compliance report to their pretreatment Control Authority. Your Control Authority contact is either a local POTW with an approved pretreatment program or Wisconsin Department of Natural Resources Regional Pretreatment Staff. The following list contains the 27 approved pretreatment programs in Wisconsin:

  • Appleton Wastewater Treatment Facility
  • City of Beaver Dam
  • Beloit Wastewater Treatment Facility
  • City of Brookfield
  • Eau Claire Wastewater Treatment Facility
  • Fond Du Lac Water Pollution Control Plant
  • Fox West Regional Sewerage Commission
  • Green Bay Metropolitan Sewerage District
  • Heart of Valley MSD WW Treatment Fac
  • Janesville Wastewater Utility
  • Kenosha Wastewater Treatment Facility
  • City of La Crosse
  • Madison Metropolitan Sewerage District WWTF
  • Manitowoc Wastewater Treatment Facility
  • Marinette Wastewater Utility
  • Milwaukee Metro Sew Dist Combined
  • Neenah Menasha Sewer Commission WWTF
  • Oshkosh Wastewater Treatment Plant
  • Racine Wastewater Utility
  • Sheboygan Wastewater Treatment Plant
  • South Milwaukee Wastewater Treat Facility
  • Superior Sewage Disposal System
  • Walworth County Metro
  • Watertown Wastewater Treatment Facility
  • City of Waukesha
  • Wausau Water Works Ww Treatment Facility
  • City of West Bend

Wisconsin Department of Natural Resources Pretreatment Staff may be found by searching the county your facility is located in and entering PRETREATMENT in the subject box: Staff eDirectory.

My practice is in compliance with the standards in the rule and has submitted a one-time compliance report. It is now changing ownership. Do I or the new owner need to submit a new one-time compliance report?

Yes. If a dental discharger transfers ownership of the facility, then the new owner must submit a new one-time compliance report to the Control Authority. See above for compliance deadlines and § NR 229.05(1)(a), Wis. Adm. Code.

Is there a website where I can submit my one-time compliance report electronically?

The Wisconsin Department of Natural Resources accepts the one-time compliance reporting form found elsewhere on this website via electronic mail if the department is the Control Authority for your facility. Check with your local approved pretreatment program personnel if your facility discharges to one of the approved pretreatment programs listed above.

Does the final rule prohibit the use of oxidizing or acidic cleaners in dental unit water lines, chair-side traps, and vacuum lines?

Yes. The clause that follows ("including but not limited to…") is not an exhaustive list of oxidizing or acidic cleaners or qualities that make a cleaner oxidizing or acidic. For example, a cleaner that is oxidizing would be prohibited even if its pH is between 6 and 8.

Does the prohibition on the use of oxidizing or acidic cleaners in dental unit water lines apply to cleaners used in the water supply lines that connect to items such as handpieces, ultrasonic scalers or air/water syringes?

No. The purpose of the best management practice (BMP) specified in § NR 229.03(2), Wis. Adm. Code is to prohibit the use of cleaners that solubilize mercury from dental amalgam in the wastewater lines in a dental facility. In developing the rule, EPA did not evaluate the use of cleaning products that may be used in dental equipment that is connected to water supply lines such as handpieces, ultrasonic scalers, or air/water syringes. While de minimus amounts of such products may eventually be indirectly discharged through a wastewater line in a dental facility, the prohibition in § NR 229.03(2)(b), Wis. Adm. Code was not intended to prohibit dental unit water line cleaning products when those products are used in water supply lines to ensure the safety of the water that dentists place in their patient's mouth.

Is the amalgam collected in the separator considered a hazardous waste under the Resource Conservation and Recovery Act (RCRA)?

Yes. Review the information on the Waste tab on this page for more details and how to comply with RCRA requirements in Wisconsin.

Amalgam Separator Posters for clinic use

Hazardous Waste Management in Dental Offices

Amalgam Resources