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

MERCURY 329
2. HEALTH EFFECTS
Neonates may also be especially susceptible to mercury toxicity. Both inorganic and organic forms of
mercury are excreted in the milk (Sundberg and Oskarsson 1992; Yoshida et al. 1992). Furthermore,
suckling rats exhibit a very high absorption of inorganic mercury as a percentage of the diet (30–40%)
compared to adult rats, which absorb approximately 1% of the inorganic mercury from the diet (Kostial et
al. 1978). The highest oral toxicity to inorganic mercury as expressed by the LD50 was for 2-week-old
rats; by 3–6 weeks of age, rats showed a dramatic drop in sensitivity to inorganic mercury poisoning
(Kostial et al. 1978). The transfer of mercury to suckling rats through milk was found to result in greater
concentrations of the metal in the brains of the offspring than in the mother (Yang et al. 1973).
Developmental neurotoxicity, similar to that seen with in utero exposure, has been observed in an infant
exposed to alkyl mercury only after birth (Engleson and Herner 1952).
Individuals with diseases of the liver, kidneys, lungs, and nerves are considered to be at greater risk of
suffering from the toxic effects of both organic and inorganic mercury. Individuals with a dietary
insufficiency of zinc, glutathione, antioxidants, or selenium or those who are malnourished may be more
susceptible to the toxic effects of mercury poisoning because of the diminished ability of these substances
to protect against mercury toxicity (see Section 2.8).
2.10 METHODS FOR REDUCING TOXIC EFFECTS
This section describes clinical practice and research concerning methods for reducing toxic effects of
exposure to mercury. However, because some of the treatments discussed may be experimental and
unproven, this section should not be used as a guide for the treatment of exposures to mercury. When
specific exposures have occurred, poison control centers and medical toxicologists should be consulted
for medical advice.
Although there are a number of treatments currently available, none are completely satisfactory and
additional development of treatment drugs and protocols is needed. The recent death of a researcher
poisoned with dimethylmercury is a case in point (Nierenberg et al 1998; Toribara et al. 1997). In spite of
prompt action and excellent medical care and monitoring, the clinical course in this patient continued to
decline, and ultimately ended in death.
In general, even the inorganic mercurials, that are considered to be more easily chelated, are difficult to
remove from the body and are not treated without some side effects. Infants and young children are