Mercury Spill Control & Cleanup
A broken light fixture, while not spread out, is a risk to employees because the dust very readily spreads and can be inhaled.
- By Mark A. Ceaser
- Jul 01, 2003
MERCURY is a known neurotoxin that is extremely toxic even in small amounts. It directly affects the central nervous and renal systems, causing developmental delays and motor and brain problems like those associated with autism. Mercury's hidden danger also lies in, when at room temperature, when exposed it vaporizes readily. Once it has become an aerosol, it is absorbed into the lungs and spreads throughout the body. Chronic mercury poisoning is more common due to long-term exposure by inhalation of dust or vapors, and knowledge to prevent such incidents is vital in mercury collection and cleanup.
Mercury is used in more than 3,000 industrial applications. The most common uses are in high-pressure sodium lamps and fluorescent bulbs; mercury-containing thermostats; spent batteries; in the medical field with sphygmomanometers, fever thermometers, and dental amalgams; and in chemicals and staining solutions such as mercury chloride. Since the early 1990s, environmental regulations have eliminated mercury as a produced product, and sources now found are as a direct result of reclamation and recycling.
Despite the changes in federal regulations to reduce the amount of mercury going into landfills and usage in consumer products, mercury-free alternative products have been slow to replace existing items--and in some case, it is impossible to do so. Knowledge of this situation makes it mandatory to educate people on the proper procedures and protection needed to clean up a mercury spill.
Cleanup Procedures
The most common form of a mercury spill is in liquid form. When liquefied, the small beads that form are difficult to pick up and contain, and measures should be taken accordingly to ensure workers are protected and do not come in contact with the contaminated area without wearing proper protection. A broken light fixture, while not spread out, is just as much of risk to the employees because the dust very readily spreads and can be inhaled.
Cleaning up this spill can be done in one of two methods, via amalgamation or insolubilization. Both methods will turn mercury into a non-vaporizing form. Insolubilization requires the mercury to be mixed into a sulfide, whereas amalgamation mixes the mercury with one or more metals into a solid that is easier to collect and dispose.
Three major surface areas that are encountered in spills are hard, such as concrete or tile; soft, such as carpet; and soils.
Before a spill takes place, proper materials need to be in order for preventive maintenance. A spill kit should be on hand at all times at any workstation where the risk of mercury spillage and exposure exists. The kit should contain the following items: goggles, nitrile gloves, disposal bags, waste labels, storage container, mercury type respirator, mercury sensing badges or instruments, absorbent scratch pads, water spray bottle, shoe covers, warning tape, and, preferably, zinc-ferrous based magnetic mercury amalgamation powder. Additional tools are recommended, such as plastic, non-sparking shovels and sweeping devices and a telescoping magnetic tool to collect the amalgam once hardened.
When a spill occurs, a set procedure should be followed to reduce the risk of exposure to the individual, and spreading of the mercury from the spill area. The first step when a spill occurs would be to isolate the contaminated area, evacuating all personnel away from the building until the spill can be contained and corrected. Marking off the area by tape or signs is followed by an immediate interview and spill inquiry report filled out with the workers' assistance. This will determine whether the spill is a simple or complex spill. Generally, amounts under one pound of mercury are considered simple, with additional considerations taken to surface areas and spreading of the mercury.
Ventilation is the primary concern at the contaminated area because the free mercury readily vaporizes and will continue to do so until collected. It is recommended to shut down the air conditioning or heating, if applicable. Open the windows to get the maximum amount of air in the room and allow the vapors to flow outside.
After the cleanup workers have donned personal protective equipment and removed all metallic objects, use mercury-sensing gauges or a gas vapor analyzer to determine the areas of contamination and residue. An alternative method is to use a high-intensity halogen light to detect the presence of mercury droplets or powder. A final method would be applying a sodium sulfide solution to the contaminated area. Discoloration in the form of dark, reddish-brown stain indicates the presence of mercury.
Once the mercury has been located, apply the magnetic amalgamation powder directly to the contaminated area. Using the spray bottle, apply a slight mist to the powder to allow the dry acid reagent to react with the metals and start to form the solid bond. Mix the powder and mercury together using the scratch pads until the metals have the appearance of a paste-like substance. With normal setting times of approximately an hour, survey the entire area for additional contamination spots, taking notice of cracks, crevices, and any orifices into which the mercury could have fallen.
If you have detected mercury in such places, the advantages of the magnetic amalgamation powder are evident. In the same method as before, form a paste and apply it to the contaminated area. Once it has hardened, use the magnetic pick-up tool to collect the mercury-bearing waste and collect it into a storage container. This application is also advisable for situations where mercury has accidentally been poured down a drain and cannot be collected. Forming the powder and using the magnetic tool like a drain snake, collect the mercury and remove the piping for disposal, along with the waste amalgam, at an approved mercury recycling and collection facility.
Upon completion of the spill area, collect all contaminated materials that have been amalgamated into a bucket with a sealed lid. This container will be the primary device to return the objects to the mercury recycler. Inspect the area and atmosphere for any residual indication of mercury vapors. Occupational Safety and Health Administration standards limit the exposure risks to vapor to no more than 0.2 mg/L. Great care must be taken to inspect all areas before declaring the site now safe for return.
Collection of the tools, gloves, boots, etc., can now be done. Put them into separate containers for disposal. A final protective application from any residual mercury would be to put down a wax-like sealant over the surface area, if applicable.
Common Medical and Outdoor Spills
Another common spill situation occurs when mercury has been spilled in a doctor's office and winds up on carpeting. The same skill and observation to detail must be followed in order to complete the task.
The preferred method is application of the amalgamation powder, then collection with a mercury-only vacuum. The affected carpet area is then cut out and ripped up, with all contaminated items including the vacuum cartridge placed in disposal containers for return to the recycler. Again, as with the hardened surface area, vapor analysis will indicate whether additional treatment is needed.
Occasionally, mercury is spilled outside and into the surrounding soil. Great care must be taken to set up a perimeter around the contaminated area and to collect the soil for cleaning. Soils vary in type and consistency; mercury commonly is found very close to the surface. The soil can be taken off site for reclamation via distillation or by using a combination of forming layers of the amalgamation powder and sand, making a slurry of the soil and water, and passing the mixture through the filter media. The effluent should be tested for mercury contamination and the filter media retained for processing at the recycler.
Waste Disposal
In dealing with any mercury spill, be mindful concern has grown in recent years about enforcing proper disposal procedures for mercury-bearing wastes. This has greatly concerned officials and agencies that fear mercury returning into the ecosystem by improper disposal methods, such as landfill burial or illegal dumping.
Stricter environmental regulations and development of new technologies have reduced the amount of mercury products available. The Environmental Protection Agency has specified fluorescent bulb disposal and reclamation of mercury from this source. Collection services are available for other mercury-containing devices, such as thermostats. The standards and locations of such facilities, as well as information on setting up a collection program, are available at state Mercury Awareness Programs' Web sites (for example, visit www.in.gov/idem/ctap/mercury/ for information on the Indiana Department of Environmental Management's MAP program). Another good source for information is the Association of Lighting and Mercury Recyclers at www.almr.org.
This article originally appeared in the July 2003 issue of Occupational Health & Safety.