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

MERCURY 326
2. HEALTH EFFECTS
at dosages of 1 mg/kg/day was reported by Bapu et al. (1994). Therapy with both B-complex vitamins
and vitamin E was found to mobilize a significant amount of mercury from all tissues examined (brain,
spinal cord, liver, and kidneys), with the maximum mobilization (about 63%, compared with controls)
being recorded in the spinal cord following vitamin E treatment. NAHT treatment also produced
significant mobilization of mercury from nervous tissue but caused an increase in mercury concentration
in non-nervous tissue.
Another group of compounds that combines with mercury (and other divalent cation species) is comprised
by those used in chelation therapy to reduce the body burden of mercury by enhancing its elimination
from the body. Such chelators include: ethylenediaminetetraacetic acid (EDTA); ethylene glycol
bis(beta-aminoethyl ether)N,N,N',N'-tetraacetic acid (EGTA); 2,3-dimercaptopropane-1-sulphonate
(DMPS); 2,3-dimercaptosuccoinic acid (DMSA); 2,3-dimercaptopropanol (British anti-Lewisite [BAL];
sometimes called dimercaprol); and N-acetylpenicillamine (NAP). While these chelating agents have a
very high affinity for Hg ++ , which makes them effective mercury chelators, they also have an affinity for
other divalent cations, many of which are essential for normal physiological function.
BAL was the first chelating agent used for mercury toxicity, and it is still widely used today for inorganic
mercury poisoning (ATSDR 1992). BAL is also believed to be effective in treating phenylmercury
poisoning, because of the rapid in vivo oxidization of phenylmercuric acetate to Hg ++ , thereby rendering
phenylmercury similar in behavior to inorganic mercury. BAL is contraindicated for cases of methylmercury
poisoning, however, because it has been demonstrated to increase the concentration of methylmercury
in the brain. Possible side effects of BAL include nausea, vomiting, headache, tachycardia,
fever, conjunctivitis, blepharospasm, and lacrimation. As an adjunct or alternative to parenterally
administered BAL, oral NAP may be used (ATSDR 1992). Side effects of NAP may include fever, rash,
leukopenia, eosinophilia, and thrombocytopenia.
DMPS and DMSA are derivatives of BAL, but they have been found to be more effective than BAL in
experimental studies. Although still considered an investigational drug, DMPS decreased the mercury
excretion half-life from 33.1 to 11.2 days in 2 workers exposed to high levels of mercury vapor (ATSDR
1992). In a study of the influence of DMPS and DMSA on renal deposition of mercury in rats, both
chelating agents were found to cause a significantly increased urinary excretion of mercury (Zalups
1993), although significant differences in the extrarenal handling of these two chelators were found.
DMPS was also shown to increase the urinary excretion of mercury 7.6-fold in a group of former chloralkali workers