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Dental Office Hazardous Waste
The Minnesota Pollution Control Agency (MPCA), publicly owned treatment works (POTW), and the metropolitan counties regulate hazardous chemical wastes at dental clinics. The most common sources of hazardous wastes at dental clinics are mercury-containing amalgam, silver-containing x-ray fixer and films, lead or lead-containing foils and vests, and pharmaceutical waste. Lead, mercury, and silver can be dangerous to human health and may pollute the environment if not properly handled and disposed of. Metals and pharmaceuticals in wastewater cannot be completely removed by POTW and commonly end up in rivers, lakes, and streams where they can negatively impact wildlife and public drinking sources.
Dental clinics may also produce hazardous wastes such as disinfectants and cold sterilants, developer system cleaners, vapor sterilizer chemicals, used electronics, and used fluorescent lamps. This fact sheet describes these hazardous wastes and discusses pollution prevention strategies, as well as management and disposal requirements.
Wastes Associated with Dental Clinics
Amalgam
Amalgam can contribute to many waste streams in the dental clinic. Amalgam particles are a major source of mercury in the sewer system. Wastewater from dental chairs where amalgam is placed into or removed from a patient’s mouth is considered hazardous waste.
Dental clinics in the Twin Cities metropolitan area may discharge their wastewater to the sanitary sewer under a program developed by the Minnesota Dental Association (MDA) and the Metropolitan Council Environmental Services (MCES) if an approved amalgam separator is appropriately used prior to discharge. Appropriate use means the separator is maintained according to the manufacturer’s specifications and the flow rate does not exceed the MCES approved rate. A list of approved amalgam separators and their approved flow rates is available.
Dental clinics outside the Twin Cities area are encouraged by both the MDA and the MPCA to use an approved amalgam separator. If an approved amalgam separator is not used, a POTW-established mercury discharge limit may have to be met or wastewater collected and managed as hazardous waste. Contact your local POTW to determine the specific requirements applicable to your clinic. Any discharge to a POTW of mercury-containing wastewater not pretreated at the dental clinic with an approved amalgam separator must be reported to the MPCA as hazardous waste.
All dental clinics on septic systems must collect and manage their amalgam-contaminated wastewater separately. Mercury-containing wastewater which has been pretreated at the dental clinic with an approved amalgam separator may be managed as universal waste and transported to any POTW or hazardous waste facility that has agreed to accept the wastewater. More information on specific requirements applicable to universal wastes may be found in MPCA Hazardous Waste Factsheet Managing Universal Wastes.
In addition to amalgam separators, traps and vacuum filters catch particles of amalgam. For traps or filters to work properly, they must be maintained according to the manufacturer’s instructions. Traps and filters must be properly managed by recycling as universal waste or managing as a hazardous waste.
Any mercury-contaminated wastes from preparing, mixing, and administering amalgam, as well as used and unused amalgam capsules contaminated with mercury must be properly managed by being recycled or managed as a hazardous waste.
Amalgam on extracted teeth should be managed as recyclable mercury waste. The teeth can be disinfected prior to shipping; however, storing the teeth in disinfectant can result in mercury leaching into the solution, possibly creating an additional hazardous waste.
Reducing Amalgam Waste
Collection Systems
The volume of amalgam contaminated wastewater can be reduced with dedicated dental chairs for amalgam placement and removal, which can be accomplished by using only one chair in the clinic for amalgam work. Dedicated collection systems are also effective and can use an on-off valve on the vacuum system to direct flow to the container dedicated to amalgam wastewater. These systems can be set up by an experienced plumber.
Substitution
Other materials such as composite, ceramic, gold, porcelain, and glass ionomers can be used in lieu of amalgam for certain restorations. While composite materials in general have a shorter life span than amalgam, especially for molar applications, composite materials are improving. Composite materials used and restored appropriately can last up to 17 years according to an article in the Journal of Dental Restoration in 2008. Dentists in countries such as Finland use composite materials in 79% of their restorations. As composites improve, more insurance companies are allowing for their reimbursement.
Other Hazardous Wastes
Disinfectants and Cold Sterilants
Formaldehyde, glutaraldehyde, hydrogen peroxide, or other disinfectants are considered hazardous waste in concentrated form. Generally, diluted product used for its intended purpose can be disposed of via the sanitary sewer. Contact you local POTW of your intent to sewer.
Fluorescent lamps
Used fluorescent lamps in Minnesota must be recycled. They can be managed as universal waste.
Hand Sanitizer
Gel and foam hand sanitizer often contain alcohol as the disinfectant, making unused portions ignitable hazardous waste. Aerosols products, including hand sanitizer, using butane-type propellants if not totally empty are also considered ignitable hazardous waste.
Foaming hand sanitizer can contain perfluorocarbons (PFC) a class of chemicals recently found in Minnesota’s ground and surface waters. These chemicals are a concern due to their persistence in the environment. Best management practices suggest using hand sanitizer and other products without PFC.
Lead Foil and Lead Shielding
In Minnesota, lead is a hazardous waste and it must be recycled or managed as such. Reclamation companies that accept used fixer or your dental supply company may recycle lead foil and shielding.
Pharmaceuticals
Many pharmaceuticals used in a dental clinics become hazardous waste when discarded or when they become “inherently waste like” meaning expired, partially used, leaking, or cannot be credited via reverse distribution. If drugs are credited through reverse distribution, they are not considered waste. Hazardous waste pharmaceuticals can include medications used for anesthesia and pain relief as well as those medications in emergency kits and crash carts. Examples of hazardous waste pharmaceuticals include albuteral inhalers, ammonia inhalants, aspirin, other pain medications, and silver nitrate sticks.
Expired drugs are often a source of waste, increasing costs and the volume of hazardous waste. Drug waste can be reduced by reviewing use history and ordering appropriately. Eliminating or selectively accepting drug samples can also reduce or eliminate pharmaceutical waste. Epinephrine waste can be reduced by eliminating crash kits.
Some pharmaceuticals are not hazardous waste; however, best management practices (BMP) dictate disposal by incineration. Pharmaceuticals should not be sent to the sewer because they are often untreated by the POTW and end up in rivers, lakes, streams, and drinking water sources where they can have a negative impact.
Ultrasonic Cleaners
Ultrasonic cleaners may be enzymatic, or contain alcohol, glutaraldehyde, or potassium hydroxide. The least toxic of these are the enzymes, although they may contain hazardous ingredients such as butoxyethanol or alkylphenylethoxylates(APE). After use these cleaners must be evaluated to determine if they are hazardous waste as they may be Minnesota Lethal, ignitable, or corrosive. Using enzymatic ultrasonic cleaners without APE, butoxyethanol, or other hazardous materials minimizes the toxicity of the waste. Used cleaners may be disposed to the sanitary sewer with notification.
Vapor Sterilizer Chemicals
The disposal of unused vapor sterilizer chemicals must be evaluated because they are sometimes highly flammable and contain formaldehyde. If small quantities of these chemicals must be disposed, contact your local POTW to determine if the sewage treatment system can handle the amount you have, if not, they must be disposed of as hazardous waste.
X-Ray Waste
Developer
Used developer can be disposed of down a drain that is connected to a POTW; however, you must notify the POTW. If your facility is not connected to a POTW, you must ship the used developer from your site for disposal.
Developer Systems Cleaner
Check the material safety data sheet (MSDS) to determine if the cleaner contains any chromium or chromate, if so it must be managed as hazardous waste. Switching to cleaners that do not contain chromium may be easier and cheaper to use due to reduced hazardous waste disposal requirements.
Some developer system cleaners are corrosive, containing acids or may contain oxidizing chemicals. These chemicals should be evaluated for hazardous waste characteristics prior to disposal. The POTW must be notified prior to disposal via the sanitary sewer and the cleaners and may require neutralization.
Used X-ray Fixer
Waste containing silver in concentrations above 5 ppm are considered hazardous waste. Recycling companies will reclaim silver from used fixer. Do not mix fixer and developer because doing so will increase the overall volume of hazardous waste. Installing a silver recovery unit at the end of the x-ray processing unit is an option for disposing of used x-ray fixer. The recovery unit must be sized to handle the quantity of fixer waste generated. Properly operating and maintaining equipment will reduce silver levels in the wastewater. Recovered silver can be sold to a metal reclaimer and treated fixer can be disposed of down a drain that is connected to a wastewater treatment plant. Your POTW must be notified of all discharges to the sewer. If you are connected to a septic system do not dispose of treated fixer down the drain.
X-ray Film
Silver can be reclaimed from x-ray film. Film with large dark areas contain more silver than film with smaller dark areas. Reclamation companies that accept used fixer will often take x-ray film.
Reducing X-ray Waste
Waste such as spent fixer, developer, cleaners, and x-rays can be eliminated by substituting digital imaging systems. Digital imaging is a dry system; no liquid chemicals are used in taking and developing the image. Because digital imaging uses a laser and computer system, no waste is produced from the process. Ultimately waste will include outdated electronics, video cards, and possibly paper images, if they are printed.
A Michigan orthodontic business that purchased a digital x-ray machine anticipated that it would eliminate the annual use of over 200 gallons of photographic development chemicals containing heavy metals such as silver and lead.
Infectious Waste
Blood and body fluids
Swabs or dressings saturated with blood or other body fluids are regulated in Minnesota by the MPCA’s infectious waste rules as well as by the Occupational Safety and Health Administration’s (OSHA) Bloodborne Pathogens standard. Generally, items that are not dripping blood or body fluids, including saliva, are not regulated as infectious waste and may be discarded in the solid waste.
Sharps
Scalpels, needles, and other sharp objects that can puncture the skin are regulated by infectious waste rules. These materials must be placed in a puncture-proof container which may be red in color or labeled with the biohazard symbol, and disposed of properly by a medical waste service. To minimize air toxins generated by the incineration of infectious waste, use of an autoclave for decontamination is preferred.
Dual Waste
Dental clinics may also generate some wastes which are simultaneously infectious and hazardous, referred to by the MPCA as “dual wastes”, which must be handled according to the requirements of both regulations.
Managing Hazardous Waste
All hazardous wastes accumulated in dental clinics must be stored in closed, properly labeled containers, and shipped from the dental clinic for disposal at an approved facility. More information on specific requirements for hazardous wastes may be found in MPCA Hazardous Waste Factsheets #1.01 through #1.10, collectively called the 10 Steps to Compliance.
For More Information
More information about disinfectants can be found in MnTAP’s fact sheet Disinfection Best Management Practices.
Washington County maintains a list of silver and mercury recyclers and medical/infectious waste transporters and disposal facilities.
For questions regarding hazardous waste management in the Twin Cities contact your county office:
| Regulatory contacts: |
| Anoka |
763.422.7093 |
| Carver |
952.361.1800 |
| Dakota |
952.891.7557 |
| Hennepin |
612.348.3777 |
| Ramsey |
651.266.1199 |
| Scott |
952.496.8177 |
| Washington |
651.430.6655 |
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| MPCA Generator Technical Assistance Unit 800.657.3864 |
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