Veterinary Compliance Assistance

Mercury in Veterinary Facilities

Human and animal healthcare facilities are under increasing pressure to eliminate mercury. Good alternatives exist for virtually every mercury containing medical product.

On this page, you will find information that will help you understand why the healthcare industry has acquired so much mercury over the years, why this has become a problem, and what your options are.



Also recommended:

OSHA Guide to Properties and Health Effects - A summary and links page with an emphasis on workplace health standards

Mercury is the only common liquid metal.  Its usefulness stems from its unique combination of weight, ability to flow, electrical conductivity, chemical stability, and its high boiling point and relatively low vapor pressure.

  • For centuries, mercury was the ideal choice for devices to measure temperature and pressure:
    • For temperature, the high boiling point of mercury means it can measure a wider range of temperatures than most other liquids.
    • For pressure, the high density of mercury means a conveniently short column can measure a wide range of pressures.  The measurement is simple:  the pressure is proportional to the length of the column, and it is hard (though not impossible) to go wrong when simply measuring a length.
  • Other medical applications take advantage of mercury's density.  For example, esophageal dilators ("bougie tubes") and similar devices use flexible tubes inserted into partially blocked passages that can apply expansion pressure when the tube is filled.  From a mechanical standpoint, mercury's weight makes it a good choice as a filling fluid.
  • Mercury's electrical conductivity combined with its ability to flow motivated its use in electrical switches that respond to tilt, such as devices to turn on a light when a cover is opened, and silent wall switches.

For these and many other applications, mercury containing devices and materials have been an integral part of healthcare facility operations for decades.  A typical large human hospital might easily have over one hundred pounds of mercury onsite, incorporated into hundreds of different devices in dozens of separate locations, unless it has undertaken a conscious and sustained effort to eliminate mercury. Veterinary clinics will have less mercury onsite, but the amount could be significant.

Risks and Liabilities

Health Risks

Mercury is typically encountered in one of three forms:

  • Metallic liquid mercury, also called "elemental" mercury, found in thermometers and sphygmomanometers
  • Inorganic mercury salts, found in mercury batteries
  • Organic mercury compounds, such as methyl mercury, produced by microorganisms such as soil bacteria, and found in fish and other foods

The forms have different properties, and therefore present different types of exposure risks:

Metallic liquid mercury, like any other liquid, evaporates.  Once in the vapor state, it passes very efficiently into the lungs (about 80% of what is inhaled stays in the body).  Some of it is then converted to inorganic salts.  The rest dissolves in fatty tissue, and can enter the central nervous system, where it can cause neurological problems ranging from subtle to severe.  In contrast, metallic liquid mercury does not pass very readily though skin, nor is it absorbed well from the digestive tract.

Inorganic mercury salts are highly toxic.  If ingested, about 10% will pass into the body through the digestive tract lining.  Much of that will collect in the kidneys and can cause severe damage there.  But inorganic mercury salts do not dissolve well in fat, and are not absorbed easily into cells.

Organic mercury compounds are fat-soluble, and pass easily into the body (90 - 95% in the case of methyl mercury) from the digestive tract.  They will be distributed throughout the body, and will cross the placental barrier, passing from mother to unborn child.

Risks to the Environment

Any emission of mercury into the environment, even at very small concentrations, can pose a threat to human health because of mercury's tendency to become concentrated in animal tissue as it moves up the food chain.  The phenomenon is known as bioaccumulation.  It is a remarkable natural process that is able to produce concentrations of certain compounds in fish tissue that are millions of times higher than the water they are swimming in.

In the case of mercury, bioaccumulation begins when certain common bacteria convert mercury into an organic form, methylmercury.  Mercury in this form can pass through the lipid membranes of various microorganisms.  This is true of other forms of mercury as well, but many of them tend to diffuse out again just as rapidly.  But once a few of the forms, like methylmercury and mercuric ion have entered a microorganism, they stay there.  The microorganisms are eaten by copepods, tiny shrimp-like animals that have been called "the base of the marine food web".  The copepods tend to excrete the membranes of the cells they eat, and the mercuric ion tends to stick to the membranes, so that form does not bioaccumulate.  But the methylmercury builds up throughout the life of the copepod.  The process continues as the copepods are eaten by organisms higher up the chain, with the methylmercury concentrations increasing at every step. As this case history indicates, it takes a set of special circumstances for bioaccumulation to occur most forms of mercury do not bioaccumulate. But methylmercury hits the jackpot.

The problem is particularly acute for fish consumption.  In 2003, there were 3,089 fish advisories in the 48 contiguous states.  This actually undercounts the number of bodies of water affected, since some advisories cover large geographic areas.  In all, fish advisories in 2003 covered 35% of the total lake acreage, and 24% of the total river miles in the country.  Mercury contamination was involved in 76% of these advisories.  These and much additional data are available from EPA's Office of Water.

It is a global, not just a local problem.  Mercury at levels exceeding the recommended maximum for consumption (1 part per million in fish tissue) has been detected even in remote locations in Canada and the U.S.  One reason is that mercury can remain in the air for a long time in the elemental form.  It slowly oxidizes through the action of ozone and other reactive pollutants, and can then settle back to the earth in rain or snow.  But it may remain in the atmosphere for a year before this happens, giving it plenty of time to travel far from its source.


Along with health and environmental risks, the presence of mercury-containing devices in a veterinary facility presents a substantial business risk associated with a growing area of litigation.  The presence of mercury exposes your facility to:

  • Immediate costs, including cleanup costs from spills, and citations from regulatory organizations
  • Long term costs, such as legal actions by workers or members of the surrounding community thought to have been exposed to mercury used on site or found in your facility's waste stream

Compliance with federal and state workplace standards for mercury is necessary, but may not be sufficient to protect a facility from future liability claims.  Mercury poisoning involves a very broad, and not very well defined, range of symptoms that can overlap with a wide variety of other causes.  The appearance of the symptoms can occur some time after the exposure.

Under the circumstances, it is not surprising that law firms specializing in personal injury cases are aggressively seeking clients with perceived symptoms of mercury poisoning.  The focus is currently on thimerosal, an ethyl mercury compound used as a preservative in vaccines. But if history is any guide, a few well-publicized damage awards would soon engender litigation involving other mercury exposure routes.

Mercury liability is a wild card. Veterinary facilities are exposing themselves needlessly to substantial future liability risks if they continue to use mercury-containing devices in applications where practical alternatives exist.

Today, the main obstacle to moving to a fully mercury-free facility is short-term cost. But when liability considerations and compliance costs are included in the assessment, it is hard to make the case for postponing the switchover.

Compliance Requirements

Hazardous Waste and Universal Waste

The presence of mercury can cause a waste material to become classified as a Hazardous Waste.  If so, the waste must be handled and disposed of in compliance with a very detailed set of regulations under the Resource Conservation and Recovery Act, or RCRA.  See the VetCA Managing Hazardous (RCRA) Wastes page for more information.

For product manufacturers to determine whether the mercury in a sample triggers a Hazardous Waste classification, the rules specify a test called the Toxicity Characteristic Leaching Procedure, or TCLP (EPA Method 1311). The test is designed to give some indication of how readily a material would tend to leach into groundwater if the waste were placed in a landfill.  The standard test involves subjecting the waste to a mild acetic acid solution (about the strength of household vinegar) at room temperature for 18 hours.  If the extract contains more than 0.2 mg per liter mercury, the waste is considered hazardous. Thus the classification will depend on both the concentration and the form of the mercury in the waste.

See the VetCA Hazardous Waste Determination page for more information on how wastes become classified as hazardous.

EPA has established a special category called "Universal Waste" to encourage recycling of certain common items.  An item that is eligible for classification as a Universal Waste is exempt from many of the cumbersome aspects of hazardous waste regulation that might otherwise make recycling impractical. Mercury-containing items that qualify include:

  • fluorescent bulbs and other mercury-containing lamps
  • mercury batteries
  • thermostats
  • pesticides

But note that universal waste rules can vary from state to state.

Air Emissions

In the early 1990's, there were over 6000 medical waste incinerators operating in the U.S., most of them small, onsite incinerators. Enough mercury had found its way into the medical waste stream that hospital incinerators had become the fourth largest source of mercury emissions to the atmosphere, accounting for 8% of the national total.

Increasing public awareness of the magnitude of mercury emissions from medical waste incinerators was a major factor in the drive to shut them down. In 2009, EPA issued amended air pollution regulations for Hospital/Medical/Infectious Waste Incinerators (HMIWI). The new standards set stricter limits on emissions for several compounds, including mercury. Specifically, the new limits for existing HMIWI was set at 0.0051 to 0.025 mg per dry standard cubic meter, depending on the size of the unit.

The number of medical waste incinerators had already been declining before the HMIWI NESHAP, but its effect was even more dramatic than anticipated. In 1997, there were approximately 2,400 incinerators burning medical waste nationwide. By 2011, the number of incinerators had declined to well less than 100.


In general, facilities that discharge wastewater are regulated in two different ways, depending on whether they release their wastewater directly to the environment ("direct discharge") or indirectly, through a municipal sewer system, known in the jargon as a Publicly Owned Treatment Works, or POTW ("indirect discharge").

Direct dischargers are required to obtain permits under the National Pollutant Discharge Elimination System (NPDES) program.  An individual facility's permit will specify limits for various compounds of concern, including mercury.  The value of the limits will depend on site-specific factors.

Effluent limits for indirect dischargers are set by their POTW.  In determining the limits, the POTW has to take its own requirements into account.  POTWs are themselves direct dischargers, and will therefore have to operate under their own NPDES permits, which will include site-specific mercury limits.  In addition, POTWs generate sludges from their biological wastewater treatment systems, and many POTWs dispose of the sludges by land application.  These sludges must also meet mercury concentration limits.  POTWs will restrict the allowable concentration of mercury in wastewater discharged to their systems in order to ensure that their requirements can be met.

Workplace Rules, Hazard Communications

Taking the different health effects into account, OSHA has developed different workplace standards for each of the three forms of mercury discussed above.  The OSHA website provides summary sheets listing exposure limits and linking to additional references for each form.

  • Standards for the Elemental Form refer to air exposure to the vapor, rather than to skin contact with the liquid metal.
  • Standards for the Inorganic Form refer to skin contact.
  • Standards for the Organic Form refer to both air exposure and skin contact.

In addition to workplace exposure standards, OSHA requires compliance with its Hazard Communication Standards.  Any workplace in which employees may be exposed to hazardous chemicals must have a HAZCOM Program in place that includes a written plan, labeling of hazards, access to Safety Data Sheets [SDS, formally Material Data Safety Sheets (MSDSs)], and appropriate training.

The OSHA website provides a compliance-oriented page with a formidable list of standards that may apply to mercury.  The links on the page tend to be nonspecific, making the page of somewhat limited utility to the general reader, but that sinking feeling you will experience as you scan through the list should serve as a useful incentive to minimize the presence of mercury in your veterinary facility wherever possible.

Other Regulations Involving Mercury

Mercury is also regulated under a bewildering variety of federal, state, and local statutes and agencies.  For example, special regulations exist for mercury contained in many common products, including:

  • Pesticides (now mostly phased out)
  • Cosmetics (as a preservative)
  • Dental products (regulated under medical device rules)
  • Food (as a trace contaminant)

Mercury is also a preservative in human and animal vaccines (Thimerosal). The CDC has a good discussion on this at Vaccines used in animals are regulated by the USDA/APHIS/CVB whereas vaccines for humans are regulated by FDA. The November 2010 VETERINARY SERVICES MEMORANDUM NO. 800.59 provides instructions for identifying samples containing merthiolate (thimerosal) to facilitate their proper disposal.

For background, a detailed discussion of mercury regulation nationwide, provided on the EPA website, is a good place to start. 

Mercury-free Alternatives

Most of mercury's unique advantages have become obsolete with developments in solid state electronics and materials science.  Mercury-free products that are equivalent to or better in performance than the old mercury devices are now readily available for virtually all applications in healthcare facilities.  For more information on eliminating mercury-containing products, and on managing any that remain, see the Mercury Elimination and Management page.

The following table lists the mercury-containing devices that typically account for a substantial fraction of the mercury in healthcare facilities.  For each device, the table indicates the properties of mercury that have made it the material of choice for those devices in the past, and the alternatives that have since become available to perform the same functions without the use of mercury.

Device Properties Alternatives
Thermometers Flow, thermal expansion coefficient, high boiling point Galinstan (uses a gallium-indium-tin alloy, otherwise similar in appearance and operation to the mercury version). 

Digital (now available with comparable accuracy to mercury).  Generally requires a battery, but solar cell models are available.

Sphygmo-manometers, barometers Flow, density, low vapor pressure Aneroid (No liquid:  uses motion of bellows.)

Electronic (No liquid:  uses solid state pressure sensor.)

Note:  Calibration issues exist for all types of sphygmos, including mercury.

Esophageal dilators Flow, density Tungsten powder in gel (tungsten is dense, more inert than mercury, and flows when dispersed in a gel)
Electrical switches Flow, conductivity Mechanical and optical devices

A few of these alternatives, such as the aneroid sphygmomanometer, have been around for decades, but have recently been improved to address issues such as durability, stability, and ease of calibration.  Some were simply not available until very recently.  But in all cases, there is no longer any technological barrier to phasing mercury out of healthcare applications.

Today, the main obstacle to moving to a fully mercury-free facility is short-term cost.  But when liability considerations and compliance costs are included in the assessment, it is hard to make the case for postponing the switchover.  The presence of mercury exposes your facility to

  • Immediate costs, including cleanup costs from spills, and citations from regulatory and accrediting organizations
  • Long term costs, such as legal actions by workers, patients, or members of the surrounding community thought to have been exposed to mercury used on site or found in your facility's waste stream

The cost of mercury spills is documented in a fact sheet from the Sustainable Hospitals project.  In several actual cases, spill costs for relatively minor incidents have generally amounted to several thousand dollars, and larger spills commonly involve tens of thousands.

Because the situation is still developing, no good liability cost projections appear to be available.

Disposal of Mercury-containing Wastes

Mercury-containing materials that are hazardous wastes must be disposed of in compliance with RCRA regulations, and discussed in the section on "Shipping Waste Off-Site" of the VetCA page on Managing Hazardous (RCRA) Wastes.  Some mercury-containing items may qualify as Universal Wastes.

Cleanup of Mercury Spills

There are several good reference sources available on the web that deal with mercury spill management.  A sampling includes:

More Resources



The Centers for Disease Control provides a series of detailed toxicological profiles for various hazardous substances.  The profile for mercury, which includes environmental fate information as well as extensive health effects data, is at

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