Dental Offices Managing Specific Wastes - X-Ray Wastes
This section covers common wastes associated with dental office x-ray systems. The topics include (link to sections below):
Use the links above to access each topic.
Most dental offices avoid the hassles and costs associated with traditional photographic x-ray systems by installing digital imaging (dental radiographs) equipment. 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 imaging process. Ultimately waste will include outdated electronics, video cards and possibly paper images, if they are printed. It is important to mention that when dental offices replace old X-ray machines, they may discover that the machines contain, or may contain, PCBs. Notably, x-ray machines manufactured before July 2, 1979, may contain PCB dielectric fluids at varying concentrations in the transformers and capacitors located in the machine, including the tube head. This fact sheet will help answer questions regarding how to replace old X-ray machines and comply with EPA regulations for PCBs.
Please note that this discussion of x-ray wastes refers mainly to federal regulations. In many cases, states or local governments have promulgated relevant rules and standards that are different and/or more stringent than the federal regulations. Therefore, to assure full compliance, you should investigate and comply with all applicable federal, state and local regulations. For more information on state hazardous waste regulations, see HERC's Hazardous Waste State Resources Locator. Further, the discussion below assumes that your dental office is classified as a RCRA very small quantity generator (VSQG). [VSQGs are allowed to generate up to 220 pounds (100 kg) of hazardous waste in any calendar month.] Not all states recognize this generator category, and, in such cases, more stringent rules will apply. For more information, see HERC's discussion of Generator Status.
Developer solutions are typically not hazardous waste because of their low silver content (usually below the regulatory level of 5 mg/l silver) and lack of other constituents or characteristics that would make it hazardous waste. However, keep in mind that the burden of determining if your waste is hazardous is your responsibility and if there is any concern, then testing should be performed (see HERC's Hazardous Waste Determination). If your used developer is hazardous, comply with federal and state hazardous waste rules (see the Hazardous Waste section).
Waste developer should not be mixed with used fixer, which is likely to be a hazardous waste, otherwise, the combined solution will be a hazardous waste. Unfortunately, some development units mix the fixer and developer after they are spent, making the entire solution hazardous waste. In such cases, consider changing or modifying your equipment (you may be able to purchase an adapter kit to keep the fixer and developer separate).
In most areas, used developer can be sewered, although, you should check with your local wastewater treatment plant for any restrictions or guidance. Flush the drain thoroughly as you dispose of the developer into the drain. Never pour x-ray developer down the drain if your facility is on a septic system because it will upset the system. In such cases, collect the developer and contract a waste hauler for proper disposal. Label any containers appropriately (e.g., "Used Developer"), if they are stored onsite.
Unused developer typically cannot go down the drain because it contains 1 to 5% hydroquinone. Although unused developer is not hazardous under RCRA (either by listing or characteristic), most states and/or local governments restrict disposal of hydroquinone. This is not an issue with used developer since hydroquinone is consumed in the developing process.
More Resources for X-Ray Developer
For additional information and guidance on x-ray fixer waste management, see EPA's publication: RCRA in Focus – Photo Processing.
The Environmentally-Responsible Dental Office: A Guide to Pollution Prevention & Proper Waste Management in Dental Offices. The guide's structure and many of the techniques discussed were originally published in June of 1999 by the National Wildlife Federation and the Vermont State Dental Society (VSDS).
General
Used fixer is generated during development of x-rays. Under the Resource Conservation and Recovery Act (RCRA) used x-ray fixer is a hazardous waste (RCRA waste code D011) because of its high silver content (the regulatory level is 5 mg/l silver, used fixer typically contains 3,000 to 8,000 mg/l of silver). As such, it cannot be sewered or disposed of as common solid waste. As with any hazardous waste, dental offices must follow applicable rules for waste determinations, management, and disposal. For more information, see Hazardous Waste.
Dental offices have three primary ways of dealing with used fixer:
- off-site disposal as a hazardous waste,
- off-site recovery, or
- on-site recovery using a silver recovery unit.
Each of these options is discussed below.
Off-Site Disposal as Hazardous Waste
From a federal standpoint, dental offices with a RCRA very small quantity generator (VSQG) status are permitted to dispose of their hazardous waste under specified conditions in:
- state or federally regulated hazardous waste treatment, storage, disposal (TSD) facilities, or
- facilities permitted, licensed, or registered by a state to manage municipal or industrial solid waste.
In general, the municipal waste facility option is not available for used fixer due to state and local restrictions, therefore, dental offices opting for off-site disposal will most likely need to use a hazardous waste TSD facility or an industrial solid waste facility. Most states also require use of a licensed or permitted transporter for moving your waste from your office to the disposal site. Further, VSQGs must ensure that hazardous waste is delivered to a person or facility who is authorized to manage it. Remember to always get documentation from the company handling your waste fixer confirming that the waste has been disposed of properly.
For VSQGs, there are some basic practices that help ensure safe management of hazardous waste:
- Storage containers should not be leaking, bulging, rusted, or incompatible with the waste stored in them. For used fixer, a closed plastic container is sufficient. Store the container in a place where it will not be damaged and cannot leak into a floor drain. You may want to place the container inside a bucket or pan to ensure the contents will not escape. It is recommended that used fixer containers be labeled with the words "Hazardous Waste - Used Fixer" and the date that the used fixer was first added to the container. It should also be noted that the Occupational Safety and Health Administration (OSHA) requires that you have appropriate labels on all containers (see 29 CFR 1910.1200(a)).
- As a VSQG, you cannot accumulate onsite more than 2,200 pounds of hazardous waste at any one time prior to disposal. If this happens, you must then follow all the requirements of a small quantity generator (SQG).
- For VSQGs there are no specific federal requirements for keeping records of the amount of hazardous waste generated by a VSQG. However, it is highly recommended that you keep all records for three years, including any analytical results, amounts of waste generated, copies of shipping manifests and any reports you have submitted. State rules for recordkeeping may vary.
If your facility is a small quantity generator (SQG), then additional RCRA rules apply. For more information, see HERC's Hazardous Waste section.
Off-Site Recycling
For VSQGs, the federal rules for off-site recycling of used fixer are the same as for the off-site disposal option described above (also, the same recommendations apply for storage, labeling and recordkeeping). In this case, the used fixer must be sent to a facility that uses, reuses or legitimately recycles the waste (or treats the waste prior to use, reuse, or recycling).
If your facility is an SQG, under federal RCRA regulations, if waste is destined for precious metals recovery, then reduced standards apply. These materials are subject to administrative requirements only, including obtaining an EPA identification number, complying with recordkeeping requirements, using a manifest when shipping materials off site, and complying with land disposal restrictions notification requirements (see 40 CFR 261.6 Requirements for recyclable materials).
On-Site Recovery
On-site silver recovery is a possibility, but it is often the most expensive alternative. Most dental offices generate between 0.5 and 1.0 gal./month of used fixer. The cost of a silver recovery unit ($200 or more) to process this quantity, plus the operation and maintenance costs (typically $100 to $400/year) generally exceed the cost of having an outside service pick-up and process the waste (usually about $4/gal.).
The most widely used type of silver recovery unit employed by dental offices is the metallic replacement cartridge, which is designed for low volume applications. This is a method of recovery which utilizes an oxidation-reduction reaction with elemental iron and silver thiosulfate to produce ferrous iron and metallic silver. The equipment consists of a plastic container, plastic-lined steel or stainless steel drum filled with metal, usually steel wool, and some plastic hose and plumbing connections. Silver is recovered when the silver-bearing solution flows through the cartridge and contacts the steel wool. The iron goes into solution as an ion, and the metallic silver is released as a solid to collect in sludge at the bottom of the cartridge or is deposited on the steel wool. The yield a user can expect is determined by the silver concentrations in solution, the volume of solution that is run through the cartridge, and the care with which the operation is managed. When silver is no longer effectively removed, the silver-bearing sludge is sent to a refiner.
Other technologies that can be used for silver recovery from fixer include electrolytic units and ion exchange. These technologies are applicable to higher volume applications.
If you use a silver recovery unit, the liquid that has run through the unit may be sewered if approved by your city/county wastewater treatment plant and the discharge meets your state and local standards (most state/local standards are between 0.1 ppm to 5.0 mg/l silver). To continuously meet discharge standards, you most likely need to use two recovery units in series to be certain that most of the silver is recovered.
Facilities with septic tanks should not dispose of the processed fixer liquid down the drain even in small quantities because it may upset the septic system.
Although recovering silver on-site can eliminate off-site shipping, in most states, hazardous waste rules still require you to report the fixer waste on your Hazardous Waste Annual Report and the Notification of Hazardous Waste Activity (if these rules apply).
More Resources for X-Ray Fixer
For additional information and guidance on x-ray fixer waste management, see EPA's publication: RCRA in Focus – Photo Processing.
Managing silver and lead waste in dental offices. This ADA Council on Scientific Affairs report provides recommendations on managing silver waste (in used fixer solution) and lead waste (in used intraoral film packets, lead aprons and lead collars) through recycling.
Cleaners for X-ray Developer Systems
Some cleaners for x-ray developer systems contain chromium (or "chromate") and are hazardous waste (D007) when discarded. Also, some developer system cleaners meet the definition of corrosiveness or reactivity (contain oxidizing chemicals) and may need to be handled as hazardous waste when spent. The onus for such determinations is on the generator of the waste, so be certain to fully investigate these materials. One source of information is the Material Safety Data Sheet (MSDS). Although MSDSs contain sparse information regarding RCRA, you can at least determine if the product contains chromium.
The following discusses two disposal options:
- off-site disposal as a hazardous waste, and
- on-site disposal as a non-hazardous waste.
Off-Site Disposal as Hazardous Waste
If your x-ray system cleaner contains chromium or is otherwise hazardous, it must be handled and disposed of according to federal and state hazardous waste rules. It is not legal to dispose of it down the drain.
From a federal standpoint, dental offices with a RCRA very small quantity generator (VSQG) status are permitted to dispose of their hazardous waste under specified conditions in:
- state or federally regulated hazardous waste treatment, storage, disposal (TSD) facilities, or
- facilities permitted, licensed, or registered by a state to manage municipal or industrial solid waste.
In general, the municipal waste facility option is not available for used chromium-bearing cleaners due to state and local restrictions, therefore, dental offices opting for off-site disposal will most likely need to use a hazardous waste TSD facility or an industrial solid waste facility. Most states also require use of a licensed or permitted transporter for moving your waste from your office to the disposal site. Further, VSQGs must ensure that hazardous waste is delivered to a person or facility who is authorized to manage it. Remember to always get documentation from the company handling your waste fixer confirming that the waste has been disposed of properly.
For VSQGs, there are some basic practices that help ensure safe management of hazardous waste:
- Storage containers should not be leaking, bulging, rusted, or incompatible with the waste stored in them. For used cleaner, a closed plastic container is sufficient. Store the container in a place where it will not be damaged and cannot leak into a floor drain. You may want to place the container inside a bucket or pan to ensure the contents will not escape. It is recommended that used cleaner containers be labeled with the words "Hazardous Waste - Used X-Ray Cleaner" and the date that the used cleaner was first added to the container. It should also be noted that the Occupational Safety and Health Administration (OSHA) requires that you have appropriate labels on all containers (see 29 CFR 1910.1200(a)).
- As a VSQG, you cannot accumulate onsite more than 2,200 pounds of hazardous waste at any one time prior to disposal. If this happens, you must then follow all the requirements of a small quantity generator (SQG).
- For VSQGs there are no specific federal requirements for keeping records of the amount of hazardous waste generated. However, it is highly recommended that you keep all records for three years, including any analytical results, amounts of waste generated, copies of shipping manifests and any reports you have submitted. State rules for recordkeeping may vary.
If your facility is a small quantity generator (SQG), then additional RCRA rules apply. For more information, see Hazardous Waste.
On-Site Disposal as Non-Hazardous Waste
Assuming that your x-ray system cleaner is non-hazardous, it may be disposed of by pouring it down the drain unless such practices are prohibited by local or state rules (check with your local sewer district). When discharging the used non-hazardous cleaner, dilute it with tap water. Never discharge used cleaner into a septic system.
Pollution Prevention
Rather than dealing with hazardous waste rules, it is easier and cheaper to use a system cleaner that does not contain chromium or other components that would cause it to be hazardous when spent. Often "environmentally safe cleaners" are as effective as the chromium-based products.
