Mercury Spill Control

Mercury finds widespread use in medical devices, industrial instruments, lighting etc. The most common applications are in high-pressure sodium lamps and fluorescent bulbs, thermostats, spent batteries, sphygmomanometers, thermometers and dental amalgams. The amount of mercury going into landfills is increasing every year because of the growing use of mercury-based healthcare, lighting and industrial products and lack of sustainable hazardous waste management practices. Tens of millions of fluorescent bulbs are discarded across the world which usually ends up in dumpsites.

Mercury is a toxin that attacks the central nervous system when ingested or inhaled.  Mercury evaporates very slowly.  If it is spilled or stored improperly, mercury evaporation can cause continual contamination of the air.  Mercury also readily seeps into lakes and waterways.  It builds up in the tissue of fish and animals that we eat, which contaminates the food chain and puts humans at risk. Mercury is toxic even in very small amounts.  It only takes 3 grams (1/25 of a teaspoon) of mercury to contaminate a 60-acre lake.  A typical mercury thermometer alone contains about 2 grams or mercury.

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 insure 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 as the dust very readily spreads and can be inhaled.

Cleanup Procedure

Cleaning up this spill can be done in one of two methods, via amalgamation or insolubilization. Both methods will turn mercury in a non-vaporizing form. Insolubilization requires the mercury to be mixed into a sulfide, where amalgamation mixes the mercury with one or more metals into a solid, which 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, the proper materials need to be in order for preventive maintenance. A spill kit should be on hand at any workstation where the risk of mercury spillage and exposure exists at all times. The first step when a spill occurs would be to isolate the contaminated area, evacuating all personal away from the building until the spill can be contained and corrected. The marking off of the area by tape or signs is followed by an immediate interview and spill inquiry report filled out with the workers assistance.

Ventilation is the primary concern of the contaminated area, as the free mercury will readily vaporize and continue to do so until collected. It is recommended to shut down the air conditioning or heating, if applicable, and open the windows to get the maximum amount of air in the room and allow the vapors to flow outside.

After the process of applying personal protective equipment on and the removal of all metallic objects from the worker, 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 the application of a Sodium Sulfide solution to the contaminated area. Discoloration in the form of dark reddish brown stain will indicate the presence of mercury.

Upon completion of the spill area, collect all contaminated materials that have been amalgamated into a bucket with 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. 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. Collection of the tools, gloves, boots, etc., can now be done and put 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.

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 carpet area affected is then cut out and ripped up, with all items, including the vacuum cartridge, contaminated into disposal containers for return to the recycler. 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 commonly, the mercury 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.