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Re: mercury thermometer hazards



Mercury thermometers aren't the most hazardous mercury in the world, but
they aren't exactly benign either.  As long as the mercury is contained
within the glass thermometer, it is no problem.  But, inevitably, that
mercury will be released, when the thermometer breaks during use,
storage, or disposal.

Volume-wise, mercury releases from thermometers are probably not the
largest environmental release of mercury.  Releases can occur to a
variety of locations--the most common are probably the air (evaporation,
vacuuming to clean up spills, incineration of mercury thermometers in
the waste stream), sewer system (spill cleanup), and landfills.  The
relative importance of the release depends on environmental medium and
physical location (e.g., out west we don't have the eastern level of
mercury releases from coal combustion, so the relative contributions are
different).

In my personal view, the most important releases are those from spills
in homes and offices when mercury thermometers break.  Spills are rarely
cleaned up properly, which means that long-term exposures to mercury
vapors can occur after a spill.  If those exposures are to children,
women who may become preganant or who are pregnant, or other sensitive
populations, they may be especially significant.

To give you an idea of the amount of mercury in the air in a room after
a mercury thermometer break, I can relate my personal experience with
the breakage of one of 4 mercury-containing glass thermostat bulbs in an
office where I used to work.  The amount of mercury released was about
the same as the amount in a mercury fever thermometer.  The break was
not recognized for a month or longer, as it didn't involve the portion
of the thermostat that was in use during the winter.  When I discovered
it, I measured the mercury level in the air in the office and found that
it was almost at the OSHA permissible exposure level (PEL).  The PEL is
set to protect healthy adults for workday exposures; it is does not
provide a margin of safety for children or other sensitive populations,
nor does it provide for exposures longer than the typical working week.  

For those who want the "quick facts," I've attached a summary of the key
health issues below.

My main question is:  why would we take a toxic metal like mercury,
encase it in a fragile shell like glass, and then stick it in children's
mouths?  Safer, equally effective, and relatively inexpensive
alternatives are available.  

Kelly Moran
TDC Environmental
__________________________

--   U.S. Agency for Toxic Substances and Disease Registry (ATSDR) and
U.S. EPA have issued a joint alert to the public regarding the hazards
of mercury to the general public. 
--     Mercury can cause serious health problems. Children and fetuses
are most vulnerable. Health effects can results from short-term or
long-term exposure. Exposure can cause harm before symptoms arise. When
symptoms do arise, health problems can include tremors, changes in
vision or hearing, insomnia, weakness, difficulty with memory, headache,
irritability, shyness and nervousness. In young children, exposure to
metallic mercury can damage the central nervous system. Long-term
mercury exposure can cause children to have trouble learning in school. 
--     Methylmercury compounds are the most toxic form of mercury, but
other forms are also very toxic. In the environment, metallic mercury is
converted to methylmercury by the action of certain types of bacteria.
U.S. EPA considers metallic mercury to be a possible human carcinogen.
Under Proposition 65, California has listed all forms of mercury as
reproductive toxicants and methylmercury compounds as carcinogens. 
--     Exposure to metallic mercury occurs primarily from breathing
contaminated air. Other forms of mercury (e.g., methyl mercury
compounds)can be absorbed by eating food (like fish), drinking water,
and from skin contact. 
--     Very small amounts of metallic mercury (e.g., a few drops) can
raise air concentrations in a room to levels that may be harmful to
health. 
--     Many serious mercury exposure incidents have occurred in homes
and schools. These incidents relate to releases of metallic mercury and
to religious practices involving metallic mercury ("azogue"). 
--     Mercury releases (e.g., from breaking a thermometer or
thermostat) are difficult to clean up properly. Improper cleanup can
lead to ongoing, serious exposures in homes and workplaces. 

Source: ATSDR and U.S. EPA National Alert
(www.atsdr.cdc.gov/alerts/970626.html)