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US Environmental Protection Agency (EPA) promulgated a standard to reduce discharges of mercury from dental offices into Publicly Owned Treatment Works (POTWs). The Rule requires emitting dental offices to use amalgam separators and the ADA's Best Management Practices for amalgam waste.1,2
The Final Rule became effective on 14 July 2017. New construction must comply immediately. Offices discharging amalgam without separators have three years to comply, while those in partial compliance have ten years. Required documentation includes use, installation and maintenance of amalgam separators, as well as baseline and monthly inspection records.1,3
Dental offices are not major mercury contributors, being responsible for less than 1% of all man-made mercury released into the environment. However, dental offices are the main source of mercury (as much as 50%) discharged into POTWs. The EPA estimates 5.1 tons of mercury, as well as 5.3 tons of other metals, present in dental waste amalgam are released into POTWs annually. Most amalgam mercury (99.5%) remains as a solid,3,4,5 even after wastewater treatment. Mercury in amalgam can also enter the environment through incineration, landfilling and wastewater sludge. Aquatic bacteria can convert any soluble amalgam mercury into methymercury, a highly toxic chemical.1,3,4
Amalgam separators can greatly reduce the discharge of mercury-containing amalgam into POTWs. They are practical, affordable and readily available. Almost all separators sold today rely on sedimentation because of its effectiveness and operational simplicity.1,2,3,5
Separators come in varying sizes. A typical office has between 3 and 5 operatories. This translates into an average start-up cost of US$2000 and an annual operational cost of US$800 (eg unit, installation and maintenance). EPA expects the final annual costs to be between US$59–US$61 million.1,2,3,4,5
There are 133,000 US dental offices of which 80% are general practices. About 40% of dentists that discharge wastewater into a POTW have already installed amalgam separators. Dental offices that discharge into POTWs, but do not place or remove amalgam (certain dental specialty offices – oral pathology, oral and maxillofacial radiology, oral and maxillofacial surgery, orthodontics, periodontics or prosthodontics) and mobile dental units need only submit a one-time certification.1,2,3,4,5
Dental offices that place or replace amalgam must not discharge scrap amalgam down a drain or use certain kinds of line cleaners. Bleach and chlorine-containing cleaners as well as acids can lead to the dissolution of solid mercury in chairside traps and vacuum lines.3,4,5
Use of dental amalgam in the US has decreased steadily since the late 1970s, being replaced by glass ionomers and composite resins. Estimates indicate amalgam use decreases approximately 2%–3% per year.1,2,5
Numerous items can contain amalgam waste. Examples include chairside traps, screen, vacuum pump filters, dental instruments, cuspidors or collection devices, such as saliva ejectors and used amalgam capsules, extracted teeth with amalgam restorations and waste items contaminated with amalgam.1,2,3,4,5,6
In addition to separators and traps, the Final Rule indicates the need to use the ADA Best Management Practices for amalgam waste handling and disposal, plus regular inspection and cleaning of traps and use of appropriate commercial waste services to recycle and/or dispose of collected amalgam (Table 1).
| Do | Do not |
|---|---|
| Do stock a variety of precapsulated alloy capsules | Do not use bulk mercury |
| Do recycle used disposable amalgam capsules | Do not place used disposable amalgam capsules into biohazard containers |
| Do salvage, store and recycle non-contact (scrap) amalgam | Do not place non-contact (scrap) amalgam into biohazard containers, infectious waste containers (sharps containers or red bags) or the regular garbage |
| Do salvage, store and recycle contact amalgam pieces from restorations after removal | Do not place contact amalgam into biohazard containers, infectious waste containers (sharps containers or red bags) or the regular garbage |
| Do use chairside traps, vacuum pump filters and amalgam separators to retain amalgam and recycle their contents regularly | Do not rinse instruments or devices containing amalgam over drains or sinks |
| Do recycle extracted teeth containing amalgam restorations. Ask your recycler if disinfection of such teeth is required. | Do not dispose of extracted teeth containing amalgam restorations into biohazard containers, infectious waste containers (sharps containers or red bags) or the regular garbage |
| Do recycle amalgam as much as possible | Do not flush amalgam waste down drain or the toilet |
| Do use line cleaners that minimize dissolution of amalgam (pH 6–8) | Do not use acid or bleach or other chlorine-containing cleaners to flush wastewater lines |
Collected materials can be recycled. However, not all recyclers accept all types of amalgam waste. Offices need to ask about collection, recycling and disposal services offered. It is important to hire a reputable service, one that follows all applicable regulations.1,2,5
The hope is that the application of the EPA Final Rule will ensure dental amalgam waste is captured before entering the waste stream. Ideally, such materials can be properly recycled.