Mercury Information
Elemental, liquid mercury is slightly toxic, while its vapor,
compounds and salts are highly toxic and have been implicated as
causing brain and liver damage when ingested, inhaled or contacted.
For this reason (along with exaggeration of the actual risk in the
media), most thermometers now use pigmented alcohol instead of
mercury, though some medical thermometers still use mercury for
reasons of accuracy.
The main dangers associated with elemental mercury are that at STP,
mercury tends to oxidize forming mercury (II) oxide, and that if
dropped or disturbed, mercury will form microscopic drops,
increasing its surface area dramatically.
Even though it is far less toxic than its compounds, elemental
mercury still poses significant environmental pollution and
remediation problems due to the fact that mercury forms organic
compounds inside of living organisms. Methyl mercury works its way
up the food chain, reaching high concentrations among populations of
some species such as tuna. Mercury poisoning in humans will result
from persistent consumption of tainted foodstuffs.
One of the most dangerous mercury compounds, dimethylmercury, is so
toxic that even a few microliters spilled on the skin can cause
death.
Mercury is a bioaccumulative toxin that is easily absorbed through
the skin, respiratory and gastrointestinal tissues. Minamata disease
is a form of mercury poisoning. Mercury attacks the central nervous
system and adversely affects the mouth, gums, and teeth. High
exposure over long periods of time will result in brain damage and
ultimately death. It can pose a major health risk to the unborn
fetus. Air saturated with mercury vapor at room temperature is at a
concentration many times the toxic level, despite the high boiling
point (the danger is increased at higher temperatures).
Mercury should therefore be handled with great care. Containers of
mercury need to be covered securely to avoid spillage and
evaporation. Heating of mercury or mercury compounds should always
be done under a well-ventilated, filtered hood. Additionally, some
oxides can decompose into elemental mercury, which immediately
evaporates and may not be apparent.