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.