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

MERCURY 356
2. HEALTH EFFECTS
The mechanism of mercury toxicity is still largely unknown. It is not known whether there are unique
mechanisms of action for the toxic effects in children that would require special consideration for
treatment modalities, but at present it appears that target site is determined more by the pharmacokinetics
(i.e., which tissues end up with the highest levels) than by a specific mechanism of action (e.g., a receptor
binding-process initiating type of mechanism).
The results of a number of accidental food poisonings indicate that children are more vulnerable, and this
vulnerability may be a function of easier access of mercury to the systemic circulation and brain, or it may
be because disruption of cell growth and organization is more critical for children in developmental stages
of growth. More data are needed to determine if the vulnerability of children is due to less plasticity to
insult of analogous target tissue in adults, or because target tissues actually receive more toxic agent.
There are not adequate biomarkers of exposure nor adequate access to biomarkers of exposure. Hair,
urine, and blood levels are gross measures of body burden and do not provide the essential information
about levels of mercury at target tissues. Research is needed into better (preferably noninvasive)
monitoring tools. Research is also needed on how to make monitoring tests readily and inexpensively
available to the general public. Mercury is one of the top ten most hazardous substances, and its levels are
increasing in the environment. There is considerable anxiety present in the general population about
potential mercury toxicity from dental amalgam, but this occurs in the absence of good information on
actual body burdens. The general public and health officials would benefit from readily available ways for
individuals to measure personal and family member mercury body burdens.
The interactions of immediate interest are those that either affect absorption from the gastrointestinal tract
or that prevent or reduce mercury toxicity. No information was identified to indicate that mercury
interacts differently with iron or zinc, for example, in a child’s body then it would in an adult, although the
difference in children’s physiology and morphology may result in a different response to that interaction.
Except for the latter, which is again a toxicokinetic question, chemical interactions do not appear to be a
data need.
There is a data need to develop better chelation therapies, better ways to prevent absorption of mercury
into the body of children, and better ways to interfere with the mechanism of action, especially for damage
to the nervous system. The current literature continues to grow with case histories of poisonings where