Sustainable Hospitals

Removing Mercury from Hospital Labs
  Mercury is prevalent in the hospital laboratory and may be difficult to find. Here are some problems you may face:
  • Material Safety Data Sheets (MSDS) will generally not identify mercury levels below 1% in the chemical or reagent. MSDSs are required to list ingredients that are health hazards and which comprise 1% or more of the chemical or reagent mixture (0.1% for carcinogens). Unfortunately 1% (10,000 ppm) can be well above some regulated wastewater limits.

  • Mercury is a common contaminant of many chemicals and reagents. The mercury usually comes from manufacturing processes that use raw materials containing mercury as a contaminant. When present as a contaminant, mercury levels are often below 10,000 ppm (or 1%), but well above the regulated ppb limits for wastewater.

  • Mercury is used in many preservatives and the preservative's name usually doesn't provide a clue that mercury is present. Mercury may be well above ppb levels in a product and yet go unrecognized as a significant source of mercury. Thimerosal is a widely-used preservative with a high level of mercury. (See Table 1, Synonyms and Trade names for Thimerosal).

  • Mercury is typically found in secondary antibodies that are bound to horseradish peroxidase (HRP), the dilutions of these antibodies, the washes from procedures using the ingredients, ELISA kits, and Western Blot kits. If you are doing Western Blots or ELISAs and are not using alkaline phosphatase as your enzyme, you are probably using materials that contain mercury. The mercury preservative thimerosal (also frequently called merthiolate) is used with horseradish peroxidase (HRP). Secondary antibodies and the buffer solutions used with the secondary antibodies are almost always preserved with thimerosal. (Normally the primary antibodies are not preserved). Reference: Melissa McCullough, Dana Farber Cancer Institute

  • Reagents with potassium (KCl, KOH) seem to consistently contain ppb ranges of mercury. Reference: Melissa McCullough, Dana Farber Cancer Institute

  • Laboratory instruments and equipment may be sources of mercury. Materials or instruments that were used with mercury reagents or mercury thermometers may retain large amounts of mercury for a long time and slowly leach out mercury (especially at acid pH), contaminating liquids that come in contact with them. One hospital found mercury contamination in water baths used to float tissue in Histology, glass coplin jars (used in staining), tissue embedding equipment (baskets, reagent containers, metal fittings on tubing), metal sinks, and electrophoresis chambers.

  • Plumbing can contain mercury. Pipes and fittings can be contaminated with mercury because of spills that occurred in the past. Metallic mercury (such as from a broken thermometer) or mercury-laden solids can accumulate in plumbing systems, especially at elbows, traps and low points. Some healthcare facilities have had to replace plumbing to effectively eliminate this problem. (For more information, visit the MWRA/MASCO Mercury Work Group website at

Steps for Tackling Mercury in the Lab

Step 1. Examine Chemicals and Reagents
Examine the container labels, MSDSs, and reagent inserts. Look for the presence of mercury. Remember that mercury may be present at troublesome levels, even if it is not listed on the MSDS, label or insert! Manufacturers are not required to list hazardous components of a product unless that component is present at a level of > 1% (0.1% for carcinogens). A product can contain up to 10,000 ppm before a manufacturer is required to list mercury as a component. Don't forget to examine cleaning agents, soap, scouring pads, and other laboratory supplies. Eliminate the use of any home cleaning products used in the lab. Home cleaning products may contain high levels of mercury and even if the mercury was flagged on an MSDS, OSHA does not require MSDSs be provided for household consumer products when the products are used in the workplace in the same manner that a consumer would use them.

Step 2. Require Vendors and Manufacturers to Disclose all Hazardous Materials in Their Reagents
When setting up contracts to purchase equipment and reagents, make disclosure of all hazardous materials in the reagents a required part of the contract. Remember that an MSDS is not sufficient unless the company has a policy of disclosing all hazardous materials on their MSDSs (and they need to sign off to the lab that they do that).

Step 3. Eliminate Instrument and Equipment Contamination
Any equipment known to have been used with mercury reagents or thermometers should be tested for mercury contamination (water baths, instrument tubing and containers, electrophoresis cells, etc.). Run rinse solutions through instruments and rinse any equipment. Collect the rinse solution, carefully label, and send out for mercury testing. Be careful not to contaminate new equipment by exposing it to mercury!

Step 4. Keep Working Even After Eliminating All Known Mercury Sources
In some cases, analysis of the laboratory waste stream continues to show mercury even after all known sources of mercury are eliminated. Here are some steps to consider:

  • Contact colleagues who are using the same methods, reagents, and instruments and tap their knowledge and ideas about the continued high mercury levels.
  • Verify that certified mercury-free reagents have been tested with a detection limit low enough to detect mercury at ppb levels.
  • Set up a good sampling plan that allows you to sort out where mercury is coming from. For example, samples should differentiate between laboratory and other end-of-pipe mercury sources. Labeling must be consistent and include sample identification, location, time and date of collection, and who collected.
    • Include the engineering department in the development of collection plans
    • Set up the collection drums in the laboratories
    • Initially, establish what laboratory departments, if any, have mercury by setting up large drums in each lab to collect and segregate all waste from that department.
    • Test all sources of water, any diluents, and all rinse solutions used in the facility
    • Collect for a length of time that ensures most if not all testing procedures are captured and that all shifts are included.
    • Once a department area is identified as a source of mercury, limit collections to 24 hours, with separate collections for bench procedures, cleaning procedures, and instruments. Changing the collection every 24 hours will identify tests not performed on a daily basis that could be a source of mercury.
    • Send samples out as soon as possible to minimize storage problems and to prevent waiting long periods of time for results.

Table 1. Synonyms and Trade Names for Thimerosal
Compiled by Melissa McCullough, Dana Farber Cancer Institute

Ethyl (2-mercaptobenzoato-S) mercury sodium salt
[(o-carboxyphenyl)thio] Ethylmercury sodium salt
o-(Ethylmercurithio)benzoic acid sodium salt
Elcide 75
Ethylmercurithiosalicyclic acid, sodium salt
Ethylmercurithiosalicylate sodium
Ethylmercurithiosalicylate sodium salt
Mercurate(1-), {ethyl[o-mercaptobenzoato(2-)]-,} sodium
Mercurate(1-), {ethyl[2-mercaptobenzoato(2-)-O,S]-,} sodium
Mercury, ethyl(hydrogen o-mercaptobenzoato)-, sodium salt
Mercury, ethyl(2-mercaptobenzoato-S)- sodium salt
Mercury {[(ocarboxyphenyl)thio]ethyl}-sodium salt
Merseptyl (VAN)
Merthiolate salt
Merthiolate sodium
Merzonin sodium
Merzonin, sodium salt
Sodium ethylmercurithiosalicylate
Sodium ethylmercuric thiosalicylate
Sodium ethylmercurithiosalicylate
Sodium merthiolate
Sodium o-(ethylmercurithio)benzoate
Sodium salt of 2-(carboxyphenyl)thioethylmercury
Sodium 2-(ethylmercurithio)benzoate
Thimerosal solution
Thimerosol solution

The SHP thanks the following people for their significant contributions to this fact sheet:
Melissa McCullough, Dana Farber Cancer Institute
David Wintz, Indiana Department of Environmental Management
Catherine Zimmer, Minnesota Technical Assistance Program

For information on mercury alternatives, visit the Sustainable Hospitals Project website at or contact us at or 978-934-3386. - Click on "MWRA/MASCO Mercury Workgroup"
This website includes resources to prevent discharge of mercury in wastewater, including a Mercury Management Guidebook, based on the successful efforts of Boston area hospitals to meet the 1 part per billion mercury discharge limit set by the local wastewater treatment plant.
This website provides tools, including purchasing language, for minimizing the volumes of waste generated and the use of persistent, bioaccumulative, and toxic chemicals. In the Mercury section of the website, check out the "Mercury Virtual Elimination Plan"


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