After three centuries, the metal also is on its way out in several measuring devices and switches, largely due to health hazards.
BALTIMORE — It was one of Daniel Gabriel Fahrenheit’s most famous inventions, in 1714. Now, after nearly 300 years on the market, the still-common mercury thermometer appears headed for extinction.
While many people probably have them in their medicine cabinets, or on their walls, the retail sale of mercury thermometers has been banned or restricted in at least 18 states, including Washington, with more such legislation pending, according to the Interstate Mercury Education and Reduction Clearinghouse.
Mercury thermometers also are on their way out in a wide variety of industries, along with a long list of other measuring devices, thermostats and switches that rely on mercury components.
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And beginning Tuesday, the National Institute of Standards and Technology (NIST), in Gaithersburg, Md., no longer will provide calibration services for manufacturers and users of mercury-in-glass thermometers — a critical service it had provided to American industry since 1901.
NIST and the Environmental Protection Agency (EPA) are taking other regulatory steps that would limit the use of those mercury-based products, and provide alternatives.
“Due to elemental mercury’s high toxicity, EPA seeks to reduce potential mercury exposures to humans and the environment by reducing the overall use of mercury-containing products, including mercury-containing thermometers,” EPA spokesman Dale Kemery said.
NIST officials expect the mercury thermometer will be officially obsolete within five years. And none too soon.
Exposure to high levels of metallic mercury vapors can cause permanent damage to the brain, kidneys and a developing fetus. Brain damage can result in irritability, behavioral changes, tremors, changes in vision, hearing and memory problems, according to the Centers for Disease Control and Prevention (CDC).
Many manufacturers and other industries have moved away from mercury devices, either out of concerns about the hazards and costs of breakage and cleanups, or because they have found something better.
“They have become obsolete in various industries as we work to remove them from the measurement stream, and find alternative thermometers,” said Greg Strouse, leader of NIST’s Temperature and Humidity Group.
If you were to compare the technologies available today, he said, “mercury is usually the least accurate of all current thermometers in the marketplace. Digital manufacturers have worked extremely hard to create products that work to meet the needs of end users, and usually better.”
“We have yet to find an application that we can’t solve with an alternate thermometer,” Strouse said.
For those still using mercury devices, NIST is working with the EPA and private industry to revise more than 700 federal product standards that have long required the use of mercury thermometers, and find alternatives.
They will identify practical alternative thermometers, and write them into the new standards.
Almost half of those standards already have been amended to allow the use of nonmercury liquids in glass, or digital thermometers using electronic sensors.
The process is expected to take several more years.
The EPA also has proposed new rules that would introduce more such flexibility into both the federal Clean Air Act and the Toxic Substances Control Act, where they currently require the use of mercury thermometers.
Accurate temperature readings are critical to many industrial processes, and commercial applications such as storage facilities for blood or vaccines.
One of the last and biggest challenges for NIST is the petrochemical industry. Natural gas, oil and other fuels expand as they warm up, so temperature measurements are critical to gauging the amount of gas or oil in, or dispensed from, a storage tank. And the industry’s measurement standards long have required finely calibrated mercury-in-glass thermometers.
NIST has begun working with the American Petroleum Institute and the American Society for Testing and Materials (an international body that develops consensus technical standards for industry) to identify thermometer technologies that can replace mercury.
“Give them credit for level of effort,” Strouse said. “There’s a lot of culture behind their measurements and a lot of money attached. They need to be sure the replacements work to the level they need them to.”
The declining demand from business and industry for calibration of mercury thermometers at NIST labs tells the tale best.
“Back in the early 1900s, they employed five people to do nothing more than calibrate mercury thermometers,” Strouse said. “When I started here 20-some years ago, there was one person in the lab calibrating close to a thousand of them a year. Last year we calibrated four.”
And there have been none in 2011. Nor is there any clamor from thermometer manufacturers to save the devices from oblivion.
Only one U.S. manufacturer of mercury thermometers — Miller & Weber, in Queens, N.Y. — remains in business. It, too, is working “extremely hard” to phase out the technology and sell customers more advanced products, Strouse said.
Thermometers aren’t the only concern. Mercury is found in a variety of measuring devices, including some barometers, strain gauges, flow meters, blood-pressure cuffs, and in some electric switches, such as the ones that turn on automobile trunk lights when lids are lifted.
For most Americans, however, the nearest mercury is probably in their home thermostats. Millions still have the iconic, round “T87F” Honeywell thermostats, or others like it, on their walls.
“It is the second-most-recognized corporate symbol in the world, after the Coke bottle,” said William O’Connor, energy-efficiency district manager in Baltimore for Honeywell.
The company works with Baltimore Gas and Electric Co. to collect and recycle 800 to 1,000 old thermostats a week — 60 percent of them containing mercury switches — as they’re replaced with programmable digital thermostats under the Baltimore utility’s Peak Rewards program.
A growing number of states have banned their sale. Washington state instituted such a ban in 2006. Three major thermostat manufacturers — Honeywell, General Electric and White-Rogers — have stopped making devices with mercury switches. They formed a nonprofit corporation, Thermostat Recycling Corp., or TRC, to collect and recycle all brands of wall-mounted mercury thermostats, including those from utilities, contractors and local hazardous-waste programs.
TRC collected 560,000 thermostats nationwide, containing more than 2 ½ tons of mercury, between 1998 and 2006.
Even so, most old mercury thermostats probably are just thrown away, and their mercury goes illegally into landfills and incinerators.
Information from Seattle Times staff is included in this report.