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

MERCURY 332
2. HEALTH EFFECTS
is metabolized, excreted through the bile, and often reabsorbed in the gastrointestinal tract (Florentine and
Sanfilippo 1991; Haddad and Winchester 1990). The half-life of lower alkyl mercurials is about
70–79 days (Aberg et al. 1969; Miettinen 1973).
For several years, diaphoresis (excretion through perspiration) was used to lower the body burden of
mercury in miners exposed to mercury vapors (Sunderman 1978). Recently, this method of therapy has
also been used to lower tissue levels of mercury in a patient exposed to metallic mercury in the
manufacture of thermometers (Sunderman 1978).
Chelation therapy is presently the treatment of choice for reducing the body burden of mercury. There
are currently a number of chelators that are either in practical use or under investigation in in vivo and in
vitro studies (Florentine and Sanfilippo 1991; Gossel and Bricker 1984; Haddad and Winchester 1990).
These chelators differ in their efficacy for various forms of mercury, routes of administration, side effects,
and routes of excretion. Depending on the chemical to which one has been exposed and the health status
of the individual, different chelators may be indicated. One popularly used chelator, dimercaprol or BAL,
has two sulfhydryl groups that can bind mercury and compete with its binding to sulfhydryl groups in
body tissues (Florentine and Sanfilippo 1991; Haddad and Winchester 1990). BAL is one of the more
effective chelators for inorganic mercury salts. BAL is administered intramuscularly and is the preferred
chelator when oral dosing is impractical (Florentine and Sanfilippo 1991; Gossel and Bricker 1984;
Haddad and Winchester 1990). Approximately 50% of the dimercaprol-mercury complex is excreted
through the kidneys, while the remainder is eliminated in the bile and feces. Thus, this chelator is
preferred when renal impairment has occurred. BAL therapy, however, has several limitations.
Significant reabsorption of mercury from the bile occurs (Shimada et al. 1993). Also, multiple toxic side
effects including urticaria, elevated blood pressure and heart rate, nausea and vomiting, headache,
conjunctivitis, lacrimation, and paresthesias have been reported (Goldfrank et al. 1990). Children may
develop fevers, and individuals with a glucose-6-phosphatase deficiency may develop hemolysis. BAL
treatment is contraindicated for elemental and organic mercury compounds because it has been shown to
increase brain levels of mercury in animal studies when used to treat exposures to phenylmercury or
methoxyethylmercury compounds (Berlin 1986; Berlin and Rylander 1964) or elemental mercury vapor
(Goldfrank et al. 1990), indicating the possibility of increased neurotoxicity.
Another currently used mercury chelator is D-penicillamine. This drug has been used somewhat
effectively to reduce the toxicity of elemental and inorganic mercury exposures. It can be taken orally, and its