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

MERCURY
2.1 INTRODUCTION
2. HEALTH EFFECTS
The primary purpose of this chapter is to provide public health officials, physicians, toxicologists, and other
interested individuals and groups with an overall perspective of the toxicology of mercury. It contains
descriptions and evaluations of toxicological studies and epidemiological investigations and provides
conclusions, where possible, on the relevance of toxicity and toxicokinetic data to public health.
A glossary and list of acronyms, abbreviations, and symbols can be found at the end of this profile.
Mercury is a metal element that occurs naturally in the environment. Metallic or elemental mercury (Hg 0 )
is the main form of mercury released into the air by natural processes. Mercury bound to other chemicals
may have valence states of either +1 (Hg +1 ) or +2 (Hg +2 ). Mercury with a valence state of +1 is referred to
as mercurous mercury, and mercury with a valence state of +2 is referred to as mercuric mercury. Many
inorganic and organic compounds of mercury can be formed from the mercuric (divalent) cation (Hg +2 ).
For information on the physical and chemical properties of mercury, refer to Chapter 3.
There are many similarities in the toxic effects of the various forms of mercury, but there are also
significant differences. In the text, tables, and figures of this profile, the metallic mercury and the inorganic
salts, including mercurous chloride, mercuric chloride, mercuric acetate, and mercuric sulfide, are organized
under the general heading of inorganic mercury. The organic mercury compounds including methylmercuric
chloride, dimethylmercury, and phenylmercuric acetate are addressed in this document under the
heading of organic mercury. In most discussion in the text, the specific effects are attributable to a
particular form, and the form is specified.
The general population is most commonly exposed to mercury primarily from two sources: (1) eating fish
and marine mammals (e.g., whales, seals) that may contain some methylmercury in their tissues or (2) from
the release of elemental mercury from the dental amalgam used in fillings. It is not known how much of the
elemental mercury released from dental amalgam is inhaled as a mercury vapor, how much is breathed out,
how much is swallowed in a liquid form, or how much is converted into a mercuric salt that is either
swallowed of directly absorbed into the oral mucosa. Exposure to mercury, however, does not necessarily
mean that adverse health effects will result. Health effects depend upon the amount of exposure, the form
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