Earlier this year, the National Institute of Standards and Technology stopped providing calibration services for mercury-filled thermometers, marking the first milestone for the phasing out of potentially hazardous mercury thermometers in the United States.

Mercury, a potent neurotoxin, has long been a standard in thermometers used in a number of industrial processes. If released into the environment though, mercury makes its way into streams, rivers and, eventually, the oceans, where it is absorbed by sea life. There, mercury accumulates in the larger fish that people consume - a source of mercury poisoning in humans. Phasing out mercury thermometers is one way to reduce mercury entering the food chain.

However, before mercury thermometers can be eliminated completely, the American Society for Testing and Materials will have to align its standards with the regulations many states already have enacted that outlaw the sale and transportation of mercury thermometers. To date, nearly half of the ASTM standards have been modified.

An alternative to a mercury thermometer is a digital unit. Most portable digital thermometers are more durable than mercury-filled thermometers. Process manufacturing of chemical, pharmaceutical, food or petroleum products requires accurate temperature measurements. Also, because temperature sensors are subject to drift over time, regular calibration or verification against a reliable reference thermometer is necessary.

For more information on alternatives to mercury-filled thermometers, go to www.epa.gov/hg/alternatives.htm.