Mercury-containing Waste: Scrap Amalgam

Dental amalgam is a mixture of two nearly equal parts of liquid mercury (D009) and a powder containing silver (D011), tin, copper, zinc and other metals.13 When amalgam restorations are placed in or removed from teeth, or during chewing, a small amount of mercury vapor is released. Although the vapor may be absorbed by inhalation or ingestion, the FDA considers amalgam restorations safe for adults and children over the age of six.

However, amalgam waste not captured or removed at the dental office is discharged into a sanitary sewer system. From the sewers the amalgam waste is transferred to publically-owned treatment works (POTWs), i.e., sewage treatment plants. POTWs remove about 95 percent of the amalgam waste, which then becomes part of the POTWs sewage sludge. The sludge may then be disposed of in landfalls, incinerated, or applied to agricultural land as fertilizer.

If the sludge is sent to a landfill, the mercury component may be released into ground water or the air; if it is incinerated, mercury may be emitted into the air; and if the sludge is used as fertilizer, evaporating mercury may become airborne. Airborne mercury is eventually deposited onto surface water, land and vegetation. Mercury is a persistent and bio-accumulative pollutant in the environment with well-documented neurotoxic effects on humans.

The EPA currently is considering a proposal that would require dental practices to comply with requirements for controlling the discharge of mercury and other metals in dental amalgam into POTWs based on the best available technology.14 Most dental offices already use some type of basic filtration system (chairside traps, vacuum pump filters); in addition, some states and local governments have enacted regulations requiring dental offices to install amalgam separators.4

Amalgam separators are devices designed to remove amalgam particles from dental office wastewater through sedimentation, filtration, centrifugation, chemical removal by ion exchange or a combination of these technologies. Amalgam separators that meet the International Organization for Standardization (ISO) standard (ISO 11143) can capture over 95 percent of the amalgam waste discharged by dental offices into sanitary sewer systems.15-17

The ADA encourages dentists to implement best management practices (BMPs) to help reduce the environmental effects of amalgam waste (Box C).15 BMP is a method or technique available to oral healthcare facilities that has been generally accepted as the best because it produces results that are superior to those achieved by other means or because it has become the standard way of doing things, i.e., the standard way of complying with legal or ethical requirements.

Box C. Best management practices for the disposal of mercury-containing scrap amalgam.15-17
  1. Stock pre-capsulated amalgam alloys in a variety of sizes to minimize the amount of hazardous mercury-containing amalgam waste generated.
    • DO NOT USE BULK ELEMENTAL MERCURY.
  2. Collect and store used (both partially filled and empty) disposable amalgam capsules in a wide-mouthed, airtight container labeled “Hazardous Waste - Amalgam Capsules.”
    • Once the container is full, have an approved hazardous waste transporter deliver it to an approved hazardous waste management facility.
      • DO NOT PLACE AMALGAM CAPSULES IN NON-HAZARDOUS OFFICE WASTE OR REGULATED MEDICAL WASTE CONTAINERS.
  3. Use chairside disposable or reusable traps, vacuum pump filters, or an ISO 11143-compliant amalgam separator to capture amalgam particles generated when removing old or carving new amalgam restorations.
    • Disposable chairside trap – when the trap is full, remove trap according to manufacturer’s recommendations and place it in a wide-mouthed, airtight container labeled “Hazardous Waste – Scrap Amalgam.”
      • Once the container is full, have an approved hazardous waste transporter deliver it to an approved hazardous waste management facility.
        • DO NOT RINSE DISPOSABLE CHAIRSIDE TRAPS THAT CONTAIN AMALGAM PARTICLES IN THE SINK.
        • DO NOT TROW DISPOSABLE CHAIRSIDE TRAPS THAT CONTAIN AMALGAM PARTICLES IN NON-HAZARDOPUS OFFICE WASTE OR REGULATED MEDICAL WASTE CONTAINERS.
    • Reusable chairside trap – when the trap is full, remove and clean trap according to manufacturer’s recommendations and place content in a wide-mouthed, airtight container labeled “Hazardous Waste – Scrap Amalgam.”
      • Once the container is full, have an approved hazardous waste transporter deliver it to an approved hazardous waste management facility.
        • DO NOT RINSE REUSABLE CHAIRSIDE TRAPS THAT CONTAIN AMALGAM PARTICLES IN THE SINK.
    • Vacuum pump filter – change filter according to manufacturer’s recommendations, put the lid on the filter and place it in the box in which it was originally shipped.
      • Once the box is full, have an approved hazardous waste transporter deliver it to an approved hazardous waste management facility.
        • DO NOT RINSE VACUUM PUMP FILTERS THAT CONTAIN AMALGAM PARTICLES IN THE SINK.
        • DO NOR TROW DISPOSABLE VACUUM PUMP FILTERS THAT CONTAIN AMALGAM IN NON-HAZARDOUS OFFICE WASTE OR REGULATED MEDICAL WASTE CONTAINERS.
    • Amalgam separators.
      • Follow manufacturer’s recommendations for maintenance and recycling procedures.