"Mercury Use in Measuring Devices" summarizes the use of mercury in devices that conduct some form of measurement, including barometers, thermometers, manometers, blood pressure cuffs, and others. This Fact Sheet covers all the types of measuring devices that contain mercury in the individual devices; the total amount of mercury in all of the devices that were sold as new in the U.S. in 2001 and 2004; companies that have phased-out the products' manufacture and sale; and non-mercury alternative devices.

The information in this Fact Sheet is based on data submitted to the state members of the Interstate Mercury Education and Reduction Clearinghouse (IMERC)¹ including Connecticut, Louisiana, Maine, Massachusetts, New Hampshire, New York, Rhode Island, and Vermont. The data is available online through the IMERC Mercury-Added Products Database.²

A number of important caveats must be considered when reviewing the data summarized in this Fact Sheet:

• The information may not represent the entire universe of mercury-containing measuring devices sold in the U.S. The IMERC-member states continuously receive new information from mercury-added product manufacturers, and the data presented in this Fact Sheet may underestimate the total amount of mercury sold in this product category.
• The information summarizes mercury use in measuring devices sold nationwide since 2001. It does not include mercury-added measuring devices sold prior to January 1, 2001 or exported outside of the U.S.
• Reported data includes only mercury that is used in the product, and does not include mercury emitted during mining, manufacturing, or other points in the products' life cycle.

As the only metal that is liquid at room temperature, mercury expands and contracts evenly with temperature and pressure changes. These characteristics have made mercury useful in devices used for measuring temperature and pressure, including the following:

Barometers measure atmospheric pressure. Mercury barometers consist of a glass tube that is closed at one end, with a mercury-filled reservoir at the base. Often, one end of the tube is open to the atmosphere so that the elemental mercury is exposed to air. The mercury rises and falls with changes in atmospheric pressure.
	Close-up of a Mercury-Filled Barometer Source: NEWMOA
Flow Meters measure the flow of gas, water, air, and steam. They are often used in water treatment, sewage plants, power stations, and other industrial applications. Some industrial settings may still have mercury flow meters in use; however, research indicates that new flow meters are manufactured without mercury. Non-mercury flow meters include digital and ball-actuated flow meters.
Hydrometers measure the specific gravity of liquids. Mercury was often used in hydrometers as a weight. However, research indicates that mercury hydrometers are no longer manufactured and sold as new. However, schools and laboratories may still have mercury hydrometers in use. Non-mercury hydrometers that used lead ballast as a weight are now used. For more information, go to: www.newmoa.org/prevention/mercury/projects/legacy/measdev.cfm#h
	Mercury Bulb Hydrometer Source: NEWMOA
Manometers measure the difference in gas pressure. Mercury manometers are generally U-shaped glass or plastic tubes containing elemental mercury with one end of the tube closed and the other open to the atmosphere. The difference in the levels of mercury in each side of the tube indicates the pressure of the gas being measured. Manometers are frequently used to measure air pressure within air ducts or compressed air lines.
	Mercury Dairy Manometer Source: Cuoco & Cormier Engineering
Pyrometers measure the temperature of extremely hot materials and are primarily used in foundry applications. Mercury is contained in the temperature-sensing device. Some manufacturers may still have mercury pyrometers in use; however, research indicates that mercury pyrometers are no longer manufactured and sold as new. New non-mercury pyrometers are either digital or optical.
Psychrometers and Hygrometers are instruments used for measuring humidity. They contain two mercury thermometers, a "dry bulb," or ordinary thermometer, and a "wet bulb" thermometer, which is kept constantly wet. A sling psychrometer is a psychrometer encased in a swiveling mechanism that is swung around rapidly to record an accurate reading for relative humidity. These devices function similarly but the names differ due to the applications in which they are used. In each device, the humidity is determined by comparing the difference in the temperatures shown by the two thermometers.
	Mercury Sling Psychrometer Source: Wikipedia
Sphygmomanometers are a type of mercury manometer that is used for measuring blood pressure. Sphygmomanometers measure both maximum arterial pressure, when the heart beats and sends blood through the arteries, and minimum pressure, when the heart relaxes and fills with blood again. Mercury is contained inside a plastic or glass tube.
Portable Sphygmomanometer Source: NEWMOA Wall-mounted Sphygmomanometer Source: Sargent-Welch Mobile Sphygmomanometer Source: Sargent-Welch
Strain Gauges measure forearm blood flow, or arterial inflow, using a technique called strain gauge plethysmography. Mercury is contained in a fine rubber tube, which is placed around the forearm. The gauge measures the increase in forearm circumference as pressure is applied. These products are not common, and only one manufacturer has informed the IMERC-member states that they manufacture mercury strain gauges. Therefore, these products are included in the "other" category in Table 2 on page 5.
Thermohydrometers are a specific type of hydrometer that contains a mercury thermometer for measuring the temperature of liquids. These products are not common, and only one manufacturer has notified the IMERC-member states that they manufacture mercury thermohydrometers. Therefore, these products are included in the "other" category in Table 2 on page 5.
Thermometers measure temperature. Mercury thermometers contain mercury encased in a thin plastic or glass tube. The mercury level rises and falls with changes in the temperature. Thermometers are used in a variety of industrial, laboratory, and commercial applications.
	Mercury Lab Thermometers Source: Sargent-Welch

Table 1 presents the average amount of mercury in each type of measuring device that is still manufactured and sold as new in the U.S. Manufacturers, importers, and distributors of mercury-added products report the amount of mercury used as an exact number or as a range.

Note: 1 gram of mercury = 0.035 ounces.

Table 2 presents the total amount of mercury in measuring devices sold in the U.S. during calendar years 2001 and 2004. More detailed information can be found in the report, Trends in Mercury Use in Products: Summary of the IMERC Mercury-added Products Database, June 2008.³

Note: 1 gram = 0.002205 pounds.

Approximately six tons of mercury contained in measuring devices was sold in 2001. This amount decreased by 1.2 tons to 4.8 tons in 2004. This represents a decline of approximately 20 percent. Since 2001, many states have passed legislation banning the use and sale of mercury-added thermometers and other measuring devices. As more state laws go into effect, mercury use in this product category will likely continue to decline.

The following IMERC-member states currently have restrictions on the sale and/or distribution of mercury-containing thermometers and other measuring devices: California, Connecticut, Illinois, Louisiana, Maine, Massachusetts, Minnesota, New Hampshire, New Jersey, New York, Rhode Island, Vermont, and Washington.⁴ In response to these mercury product bans and phase-outs, many companies have ceased manufacturing mercury containing measuring devices and/or stopped selling these products to these IMERC-member states.

The following is a list of companies and measuring device products that have reportedly been eliminated from the U.S. market since 2001:

Princo Instruments, Inc. reported to IMERC-member states that they phased-out the manufacture of their mercury thermometers in 2002. They completed a company-wide phase-out of all products containing mercury, including barometers, manometers, and psychrometers by 2007.

Cooper-Atkins Corp. reported to IMERC-member states that they phased-out the manufacture of their mercury thermometers (e.g., maximum holding thermometers) in July 2003.

Miljoco Corp. reported to IMERC-member states that they phased-out production of their mercury-containing industrial thermometers in 2003.

Motion Pro reported to IMERC-member states that they stopped sales of their mercury manometers to Connecticut as of July 1, 2004, in conjunction with Connecticut's mercury product ban.

Anderson Instruments reported to IMERC-member states that they phased-out the manufacture of their mercury thermometers in January 2006.

Meriam Process Technologies reported to IMERC-member states that they phased-out the manufacturer of their mercury manometers and replacement tubes in 2006.

Brooklyn Thermometer Company reported to IMERC-member states that they went out of business in November 2007. Therefore, their mercury-containing "precision thermometers" are no longer manufactured or sold in the U.S.

Taylor Precision Products reported to IMERC-member states that they phased-out mercury in their consumer thermometers in 2007. They are currently working to replace their high-volume, commercial mercury thermometers with a non-mercury alternative.

There are non-mercury alternatives that may be suitable for replacing the traditional mercury-added measuring devices. Many factors should be considered when switching to a non-mercury measuring device, including the relative costs, availability, and product effectiveness.

Table 3 lists the non-mercury alternatives to common measuring devices.

*Note: Research indicates that mercury-containing flow meters, hydrometers, and pyrometers are no longer manufactured or sold in the U.S.

For more information about the non-mercury alternatives for measuring devices found in schools, go to: http://www.newmoa.org/prevention/mercury/schools/MercuryAlternativesReport.pdf.