The Environmental Protection Agency (EPA), Centers for Disease Control and Prevention (CDC) and Food and Drug Administration (FDA), have closely monitored and tested the effects of mercury and its use in the dental industry for many years. Since the early 1990s, these agencies have been researching the link between human and environmental health issues and mercury that originated in dental offices as dental amalgam [uh-mal-gum]. Dental amalgam is a dental filling material which contains a mix of 50% mercury, plus a powder containing silver, tin, copper and other metals. It has been used for over 150 years to fill cavities caused by tooth decay in hundreds of millions of patients around the world .
Elemental mercury is the primary component of dental amalgam. Mercury is a naturally occurring metal in the environment and can exist in liquid, gas or solid form when combined with other metals. Everyone is exposed to mercury through air, drinking water, soil and food. The concern is (1) how much mercury consumption is too much before it causes mercury poisoning, and (2) are mercury levels increasing as a result of interactions with other elements in the environment?
Mercury is released into the environment whenever a dentist removes an old amalgam filling from a cavity, or when excess amalgam is removed during the placement a new filling. There is a concern that low levels of vapor can be inhaled and absorbed by the lungs even years after an amalgam filling is placed in a patient’s mouth, potentially causing long-term damage to the brain and kidneys. Due to the lack of scientific data surrounding this concern, there has been little done to limit the use or disposal of amalgam over the years. In 2009, the FDA issued a final rule that classified dental amalgam as a class II device along with a document that designates special controls for dental amalgam. The Agency for Toxic Substances and Disease Registry (ATSDR) and the EPA have established mercury exposure levels aimed at protecting the most mercury-sensitive populations from the adverse effects of mercury vapor, namely pregnant women, developing fetuses and all children under 6 years old .
The EPA is adding technology-based pretreatment standards under the Clean Water Act (CWA) for discharges of pollutants into publicly owned treatment works (POTWs) from existing and new dental practices that discharge dental amalgam . These new standards now 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 or best available demonstrated control technology.
EPA identified one technology called an amalgam separator which is currently on the market and has been proven to effectively capture dental amalgam before it reaches the wastewater. Therefore, the EPA developed a regulation based on a separation and continual maintenance model that achieves a 99% reduction of total mercury from amalgam process wastewater.
Compliance with the pretreatment standard for new and existing offices will be met by completing the following tasks:
• Installing and properly maintaining an amalgam separator that is ISO 11143 certified to meet at least 99.0% reduction of total mercury.
• Properly managing and recycling of scrap amalgam (i.e., not flushing scrap amalgam down the drain), and cleaning chair side traps with non-bleach, non-chlorine cleaners. These steps are necessary to prevent mercury discharges that may bypass the amalgam separator. The ADA recommends following its Best Management practices to recycle scrap amalgam waste (e.g., using a PureWay Amalgam Recycling System)
The EPA has identified amalgam separators as an affordable and practical technology with an approximate average annual cost of $700 per office.
It is understood that a number of dental offices may already have an amalgam separator in place, whether to comply with existing state or local amalgam regulations, or because they voluntarily installed an amalgam separator. According to the new EPA ruling, dental offices with existing amalgam separators will not be penalized as long as the separator is certified to remove 95% of total mercury. The EPA will not require existing separators that still have a remaining useful life to be retrofitted with a new separator, (1) because of the additional costs incurred by dental facilities that proactively installed an amalgam separator ahead of the EPA’s proposed requirements, and (2) because of the additional solid waste that would be generated by disposing of the existing separators. As long as these offices with existing separators continue to properly operate and maintain the separator and comply with BMPs and recordkeeping requirements, these facilities will be considered in compliance with the new ruling until ten years from the effective date of the final rule.
More details on amalgam separator
The amalgam separator is placed at some point in the vacuum line, before the vacuum line intersects with plumbing in other parts of the building, and separates solids from wastewater. The typical plumbing configuration in a dental office involves a chair-side trap for each chair, and a central vacuum pump with a vacuum pump filter. Chair-side traps and vacuum pump filters remove approximately 78% of dental amalgam particles from the waste stream . These chair-side traps cannot be cleaned or washed; they must be recycled to ensure the amalgam particles are properly managed.
Most separator designs rely on the force of the dental facility’s vacuum to draw wastewater into the separator. These separators are estimated to reduce the discharge of metals to POTWs by at least 8.8 tons per year, about half of which is mercury.
Most amalgam separators use sedimentation processes to filter solids. The high specific gravity of amalgam allows effective separation of amalgam from suspension in wastewater. The weight of amalgam is 2x – 3x that of most sediments found in dental wastewater, which allows the particles to separate and settle at the bottom of the canister. After the solids settle, the wastewater is either pumped out, decanted during servicing, or is pulled through the separator. In addition to sedimentation and filtration units, there is a new type of separator that utilizes a centrifugation. A centrifuge-based separator spins the water so that the heavier amalgam particles are forced to the sides of the separator. No matter which separator is chosen, it is imperative that it meets the ISO 11143 standard and testing which certifies proper removal of 99.0% or more of total mercury .
Requirements for Dentists:
Dental offices that place or remove amalgam fillings are required to install and properly maintain an amalgam separator. Depending on the brand, a separator can be purchased from virtually any supply vendor or purchased directly from the manufacturer. Whichever separator is purchased, it is important that the system is installed promptly in order to comply with the new regulations. Proper documentation management is an integral part of this program to ensure that (1) a certificate of recycling is kept on file, and (2) a replacement canister is purchased once the marked fill line is reached or 12 months from the date of installation, whichever occurs first.
The regulations do not specify a minimum amount of time needed before to replacing a used filter/canister, but the regulations do state and mandate that the manufacturer guidelines for replacement be followed. Since each amalgam separator is required to conduct testing for the ISO certification based on a 12 month replacement maximum, most amalgam separators are required to be replaced every 12 months or when the canister is full. This not only ensures that the separator is functioning as certified, but also to prevent the separator from moving into bypass mode, which would allow the wastewater to flow unrestricted or filtered directly through the separator. The EPA recommends that an amalgam separator in use should be monitored monthly to ensure the canister is replaced per the manufacturer’s instructions for use, and that a backup canister is kept on site to ensure proper replacement is conducted at the appropriate time.
Most separators are compatible with both large- and small- capacity dental offices, and with both dry vacuum and wet vacuum systems. That being said, it is best to check with the manufacturer or distributor of the amalgam separator to make sure the appropriate system is purchased for an office.
The EPA guidelines recommend using the ADA’s Best Management practices for managing amalgam, which are detailed in the table below:
ADA Best Management Practices for Amalgam Waste
|Do use precapsulated alloys and stock a variety of capsule sizes||Don’t use bulk mercury|
|Do recycle used disposal amalgam capsules||Don’t put used disposable amalgam capsules in biohazard containers|
|Do Salvage, store, and recycle non-contact (scrap) amalgam||Don’t put non-contact amalgam waste in biohazard containers, infection waste containers (red bags), or regular garbage|
|Do salvage (contact) amalgam pieces from restorations after removal and recycle their contents||Don’t put contact amalgam waste in biohazard containers, infectious waste containers (red bags), or regular garbage|
|Do use chair-side traps, vacuum pump filters, and amalgam separators to retain amalgam and recycling their contents||Don’t rinse devices containing amalgam over drains or sinks|
|Do recycle teeth that contain amalgam restorations (Note: Ask your recycler whether or not extracted teeth with amalgam restorations require disinfection)||Don’t dispose of extracted teeth that contain amalgam restorations in biohazard containers, infectious waste containers (red bags), sharps containers, or regular garbage|
|Do manage amalgam waste through recycling as much as possible||Don’t flush amalgam waste down the drain or toilet|
|Do use line cleaners that minimize dissolution of amalgam||don’t use bleach or chlorine- containing cleaners to flush wastewater lines|