Description
Much of the notoriety of methylmercury has been generated
from three separate mass poisoning events, two in Japan and
one in Iraq. These events, at Minamata Bay in Niigata prefecture,
and in Basra, demonstrated the potential lethality of
methylmercury after it was a known toxic substance, and,
though mercury is still an important risk factor for developmental
toxicity, since the 1970s there have not been any
large-scale poisonings of this type. Methylmercury is formed
naturally in aquatic environments through the action of
anaerobic bacteria on inorganic mercury.
Chemical Properties
Water soluble, lipid soluble, high vaporpressure.
Uses
Organomercury compounds such as aryl and alkoxy-aryl have
been used in medicine, agriculture, and laboratory research.
Their use in medicine and in fungicides has been greatly
reduced or eliminated.
Definition
Either of two com-pounds that contain the methyl group and commonsalts of monomethylmercury.
Hazard
Mutagen; possible carcinogen; teratogen;central nervous system poisons that easily passthrough the blood–brain barrier.
Safety Profile
A poison. An
experimental teratogen. Experimental
reproductive effects. Mutation data
reported. Used as a fungicide. When heated
to decomposition it emits toxic fumes of
Hg.
Potential Exposure
Methyl mercury has been
used as seed disinfectants and for fungicides. It has
also been used in organic synthesis.
Environmental Fate
Inorganicmercury introduced as a pollutant into natural waters is
scavenged by particulate matter and deposited into bottom
sediments. Free Hg2+ is gradually released from this pool of
slightly soluble inorganic mercury and is then transformed by
microbial activity into methylmercury. Methylmercury diffuses
into thewater column and is takenupbyfishand other organisms
(either directly through water or through the food chain), and
accumulated in their tissue. The degree to which mercury is
transformed into methylmercury and transferred up the food
chain through bioaccumulation depends on a variety of factors,
including water chemistry and the complexity of the food web.
Shipping
UN2025 Mercury compounds, solid, n.o.s.,
Hazard Class: 6.1; Labels: 6.2-Poisonous materials,
Technical Name Required.
Toxicity evaluation
All mercury compounds exhibit high affinity for sulfhydryl
groups in proteins. As a result, a variety of enzymes and
structural proteins containing free sulfhydryl groups can be
modified and their functions affected. Inhibition of protein
synthesis is an early biochemical event following exposure. The
integrity of the blood–brain barrier can be disrupted by
methylmercury, which results in the alteration of amino acid
uptake and subsequent brain metabolism. Methylmercury can
alter cell division during critical stages of central nervous
system (CNS) development, at least in part through inhibition
of microtubule function. However, there is uncertainty whether
methylmercury or the mercuric ion following cleavage from
methylmercury is the ultimate toxicant.
Incompatibilities
Incompatible with oxidizers (chlorates,
nitrates, peroxides, permanganates, perchlorates, chlorine,
bromine, fluorine, etc.); contact may cause fires or explosions. Keep away from alkaline materials, strong bases,
strong acids, oxoacids, epoxides. May be sensitive to light.
