Mercury is a dangerous neurotoxin that can have damaging affects on both the central nervous system and renal system of humans. Exposure to mercury can cause serious developmental delays in children, and high level exposure is life threatening. When exposed to air, mercury vaporizes, readily becoming a dangerous aerosol that can be absorbed into the lungs and spread throughout the body. This is known as chronic mercury poisoning and it is most common because, in such cases, people do not experience the damaging effects of their exposure immediately and are thus unaware of the problem. Most of these exposures occur through the inhalation of vapors or contaminated dust.
Mercury is used in more than 3000 industrial applications including the manufacturing of high-pressure sodium lamps, fluorescent bulbs and temperature control thermostats. In the medical field, it is commonly found in sphygmomanometers, fever thermometers and dental amalgams. It is also found in chemicals and staining solutions, such as mercury chloride. Since the early 1990’s, environmental regulations have restricted the production of new mercury, and today sources exist only as a direct result of recycling mercury from existing (mercury based) products. Although the number of mercury based products has been greatly reduced since the early 1990’s, there are still enough mercury based products being used today to warrant educating people on the proper procedures and protection needed to clean-up a mercury spill.
The most common form of a mercury spill is liquid. When liquefied, the small beads that form are difficult to pick up and contain, so measures should be taken to insure that workers are protected and do not come in contact with the contaminated area. A broken light fixture, while not spread out, is just as much of a risk to people because the dust spreads and can easily be inhaled. Cleaning up this type of spill can be done in one of two methods: via amalgamation or insolubilization. Insolubilization requires the mercury to be mixed into a sulfide, while amalgamation involves mixing the mercury with one or more metals to form a solid, which is easier to collect and dispose. Both methods will turn mercury into a non-vaporizing form. The three most common areas that are encountered in spills are hard (such as concrete or tile), soft (such as carpet) and soils.
In order to properly handle a mercury spill a spill kit should be on hand at every workstation where the risk of mercury spillage and exposure exists. The kit should contain: goggles, nitrile gloves, disposal bags, waste labels, storage containers, 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 such as plastic shovels, sweeping devices, and a telescoping magnetic tool to collect the amalgam are recommended.
When a spill occurs, a set procedure should be followed to reduce the risk of exposure to the individuals and stop the spreading of mercury from the spillage area. The first thing to do when a spill occurs is to isolate the contaminated area; evacuating all personnel from the building. Secondly, the area should be restricted by tape and signage, and everyone who witnessed the spill should be interviewed so that an incident report can be completed. In determining whether the spill is simple or complex, a spill is generally considered simple if the amount of spillage is less than one pound, although consideration must be given to the surface area involved when making this determination.
Ventilation should be your primary concern in a contaminated area because free mercury will readily vaporize until collected. It is recommended that forced air heating and cooling systems be turned off as soon as a spill occurs. Also, windows in the contaminated area should be opened to allow outside air to flush out any harmful vapors.
After applying personal protective equipment and removing metallic objects, workers should use mercury sensing gauges or a gas vapor analyzer to determine the areas of contamination. 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 the application of a sodium sulfide solution to the contaminated area. Discoloration, in the form of a dark reddish brown stain, will indicate 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 form a solid bond. Secondly, 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 lasting approximately one hour, you can now survey the entire area for additional contamination spots, making notice of cracks, crevices and any orifices that the mercury could have fallen into. If detection has discovered mercury in such conditions, the advantages of the magnetic amalgamation powder are evident. In the same method as before, form a paste and apply to the area contaminated. Once hardened, use the magnetic pick up tool to collect the mercury bearing waste and dispose of it into a storage container. This approach is also recommended in situations where mercury has been accidentally poured down a drain and is difficult to collect. Forming the powder and using the magnetic tool like a drain snake, collect the mercury and remove the piping and waste amalgam for disposal at an approved mercury recycling facility.
Upon completion of the clean up, collect all contaminated materials that have been amalgamated, and place them in a sealed container. This container will be the primary device for returning the contaminants to the mercury recycler. Inspect the area and atmosphere for any residual indication of mercury vapors. The Occupational Safety and Health Administration (OSHA) standards limit the exposure risks to vapor to be no more than 0.2 mg/L. Great care must be taken to inspect all the areas before declaring the site now safe for return. Tools, gloves, boots, etc., can now be collected and put into separate containers for disposal. A final protective measure, if applicable, would be to seal the floor with a wax sealant.
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. Application of the amalgamation powder, and then collection with a mercury only vacuum is the preferred method. The affected carpet area is then cut out and properly disposed. Again, as with the hardened surface area, vapor analyzing will indicate if 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 and mercury is commonly found very close to the surface. The soil can be taken off site for reclamation via distillation or by using a combination of layering of amalgamation powder and sand, combined with a slurry of contaminated soil and water, the solution can then be filtered through an approved filter media. The effluent should be tested for mercury contamination and the filter media retained for processing at the recycler.
In dealing with any mercury spill, a growing concern in recent years has been the proper disposal procedures for mercury-bearing wastes. The issue of mercury returning into the ecosystem by improper disposal methods, such as landfill burial or illegal dumping has been a concern of government officials. With stricter environmental regulations and development of new technologies to reduce the amount of mercury products, the EPA Greenlights program has set standards to specify regulations for fluorescent bulb disposal and mercury reclamation. Other recycling policies concerning mercury-containing devices, such as thermostats, have brought about the growth of collection service centers. The standards and locations of such facilities, or information to set up a collection program, can be found at the Mercury Awareness Program web site or by contacting the Association of Lighting and Mercury Recyclers at www.almr.org.
Mark A. Ceaser, Gouldsboro, PA is General Manager of OMNI/ajax and co-founder of Absolute Sorbent Technologies, Toronto, Ontario, Canada, manufacturers of hazardous waste spill clean-up and waste disposal products. A US patent holder, Mr. Ceaser has written technical articles on spill control and disposal for such wastes as blood borne pathogens and mercury. Information on the products and company can be found online at www.omni-ajax.com.