Children’s Health Article
590
VOLUME 113 | NUMBER 5 | May 2005 • Environmental Health Perspectives
Mercury is a ubiquitous environmental toxi-
cant (Goldman et al. 2001). It exists in three
forms, each of which possesses different
bioavailability and toxicity: the metallic ele-
ment, inorganic salts, and organic compounds
(methyl mercury, ethyl mercury, and phenyl
mercury) (Franzblau 1994). Although volca-
noes and other natural sources release some
elemental mercury to the environment, anthro-
pogenic emissions from coal-fired electric
power generation facilities, chloralkali produc-
tion, waste incineration, and other industrial
activities now account for approximately 70%
of the 5,500 metric tons of mercury that are
released into the earth’s atmosphere each year
[United Nations Environmental Programme
(UNEP) 2002]. Elemental mercury is readily
aerosolized because of its low boiling point, and
once airborne it can travel long distances to
eventually deposit into soil and water. In the
sediments of rivers, lakes, and the ocean, metal-
lic mercury is transformed within microorgan-
isms into methyl mercury (Guimaraes et al.
2000). This methyl mercury biomagnifies in
the marine food chain to reach very high con-
centrations in predatory fish such as sword-
fish, tuna, king mackerel, and shark (Dietz
et al. 2000; Gilmour and Riedel 2000;
Mason et al. 1995; Neumann and Ward
1999). Consumption of contaminated fish is
the major route of human exposure to methyl
mercury.
The toxicity of methyl mercury to the
developing brain was first recognized in the
1950s in Minamata, Japan, where consump-
tion of fish with high concentrations of methyl
mercury by pregnant women resulted in at
least 30 cases of cerebral palsy in children;
exposed women were affected minimally if at
all (Harada 1968). A similar episode followed
in 1972 in Iraq when the use of a methyl
mercury fungicide led to poisoning in thou-
sands of people (Bakir et al. 1973); again,
infants and children were most profoundly
affected (Amin-Zaki et al. 1974, 1979).