revised final - Agency for Toxic Substances and Disease Registry ...

MERCURY 305
2. HEALTH EFFECTS
for psychological development) (Thorpe et al. 1992). Mercury exposure was not measured, but the child was
born with hair levels of 3 mg/kg (3 ppm) of mercury. This hair level was comparable to that observed in
populations consuming fish once a week (WHO 1990) and suggests that exposure in this case may have been
relatively low.
In the in vivo study by Sager et al. (1982), it was concluded that methylmercury may be acting on mitotic
spindle microtubules leading to cell injury in the developing cerebellar cortex. Cell injury observed in the
external granular layer of the cerebellar cortex of 2-day-old rats was attributed to a reduced percentage of
late mitotic figures (arrested cell division) due to the loss of spindle microtubules. Mitosis and migration of
granule cells in the cerebellum end within weeks following birth; therefore, this observation may suggest
potential differences in the sensitivities of children and adults to mercury-induced neurotoxicity.
Regardless of whether mercury exposure is through inhalation of mercury vapors, ingestion of organic
mercury or mercury salts, or dermal application of mercury-containing ointments, patients (primarily
children) may exhibit a syndrome known as acrodynia, or pink disease. Acrodynia is often characterized by
severe leg cramps; irritability; and erythema and subsequent peeling of the hands, nose, and soles of the feet.
Itching, swelling, fever, tachycardia, elevated blood pressure, excessive salivation or perspiration,
morbilliform rashes, fretfulness, sleeplessness, and/or weakness may also be present. It was formerly
thought that this syndrome occurred exclusively in children, but recent reported cases in teenagers and adults
have shown that these groups are also susceptible.
Developmental effects from prenatal or postnatal exposures to mercury are unique to children. During
critical periods of structural and functional development in both prenatal and postnatal life, children are
especially vulnerable to the toxic effects of mercury. Inhalation exposures are relatively rare outside of the
occupational setting so the exposure route and form of mercury most commonly associated with a risk for
development effects is the ingestion of methylmercury on the surface of contaminated foods (methylmercury
used as a fungicide on seed grain) or accumulated within the food (methylmercury in fish, wild game, and
marine mammals). The exposure route and form of mercury most commonly associated with maternal
exposures is to foods contaminated with methylmercury fungicides (Bakir et al. 1973) or foods that contain
high levels of methylmercury (Grandjean et al. 1997b, 1998; Tsubaki and Takahashi 1986).
The first such incident was reported in Sweden in 1952 when flour from grain treated with an unspecified
alkyl mercury compound ingested by a pregnant woman was associated with developmental toxicity. An