Dental offices may use a wide variety of mercury-containing products or chemicals. Most commonly used is dental amalgam which contains approximately 50% mercury, along with varying amounts of silver, tin and copper. Even dental offices that no longer use amalgam may still have mercury in pipes and drains from its use long ago.
When amalgam is allowed to escape down a drain, it comes in contact with water and the mercury then becomes a contaminant that must be removed by your local wastewater treatment plant. Once in the water, it can be difficult and costly to remove or reduce mercury to safe limits.
Where can mercury and amalgam be found in a dental office?
Amalgam waste can be found in different forms, including:
- Non-contact amalgam (scrap amalgam) that is excess mix leftover at the end of a dental procedure);
- Contact amalgam (amalgam that has been in contact with the patient);
- Chair-side traps that capture amalgam waste during amalgam placement or removal procedures;
- Vacuum pump filters or traps containing amalgam sludge and water;
- Amalgam sludge (the mixture of liquid and solid material cleaned from vacuum pump filters or other amalgam capture devices);
- Empty amalgam capsules (leftover from precapsulated dental amalgam); and
- Bulk mercury on hand if you were in practice before the pre-mixed capsules.
Mercury and amalgam may also be found in sewer pipes. Mercury can settle at a low point such as as a sump or trap and remain in the pipes of a facility for many years. Often, the slow dissolution of the mercury in a sump, trap or pipe is enough to cause exceedance of mercury limits in wastewater even after best management practices are implemented. Hot spots in a facility's piping may appear where laboratories or equipment maintenance areas were located. Whenever traps or sumps are moved or cleaned, the solid contents should be treated as a hazardous waste unless proven otherwise.
What can dental offices do to help?
- Use precapsulated alloys and stock a variety of capsule sizes;
- Recycle used disposable amalgam capsules;
- Salvage, store and recycle non-contact amalgam (scrap amalgam);
- Salvage (contact) amalgam pieces from restorations after removal and recycle the amalgam waste;
- Use chair-side traps to retain amalgam and recycle the content;
- Recycle contents retained by the vacuum pump filter or other amalgam collection device, if they contain amalgam;
- Recycle extracted teeth containing amalgam restorations along with the chairside trap waste (Note: Confirm that your recycler will accept extracted teeth with amalgam restorations.);
- Manage amalgam waste through recycling as much as possible;
- Use line cleaners that minimize dissolution of amalgam;
- Consider installing a mercury separator unit;
- Complete a mercury assessment of your facility by using the Mercury Checklist [DOC];
- Phase out mercury-containing products and equipment, when possible;
- Substitute mercury-free batteries for mercuric oxide (mercury-zinc) batteries;
- Use safe, non-mercury cleaners and degreasers in labs, housekeeping departments and maintenance areas;
- Replace mercury-containing thermostats and switches with mercury-free alternatives when remodeling or replacing old equipment;
- Purchase septic tank and sump pumps that contain magnetic dry reed switches, optic sensors or mechanical switches instead of mercury tilt switches;
- Examine use of other mercury-containing products in your facility, including generators, high intensity lamps, and manometers and consider switching to mercury-free alternatives; and
- Implement a mercury-free purchasing policy.