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

MERCURY 161
2. HEALTH EFFECTS
No studies were located regarding the following effects in humans or animals after dermal exposure to
inorganic or organic mercury:
2.2.3.5 Reproductive Effects
2.2.3.6 Developmental Effects
2.2.3.7 Genotoxic Effects
Genotoxicity studies are discussed in Section 2.5.
2.2.3.8 Cancer
No studies were located regarding cancer in humans or animals after dermal exposure to inorganic or
organic mercury.
2.3 TOXICOKINETICS
Absorption is high (approximately 70–80%) for inhaled metallic mercury vapor, and negligible for oral
exposure to liquid metallic mercury. Absorption of inorganic mercuric salts may range from 2 to 38%
depending upon the form and test conditions. Oral absorption of organic mercury is nearly complete, but
respiratory absorption data are lacking, particularly for the alkyl mercurials.
The distribution data for metallic, inorganic, and organic mercury are consistent in identifying the kidney as
the organ with the highest mercury bioaccumulation. Because of its high lipophilicity, metallic mercury can
also be transferred readily through the placenta and blood-brain barrier. The oxidation of metallic mercury
to inorganic divalent cation in the brain can result in retention in the brain. Inorganic mercury compounds
can reach most organs; however, their low lipophilicity reduces their ability to penetrate barriers to and
accumulate in the brain and fetus. The distribution of methylmercury is similar to that of metallic mercury;
a relatively large amount of mercury can accumulate in the brain and fetus (compared to inorganic mercury)
because of its ability to penetrate the blood-brain and placental barriers and its conversion in the brain and
fetus to the inorganic divalent cation.
Metallic mercury can be oxidized to inorganic divalent mercury by the hydrogen peroxidase-catalase
pathway, which is present in most tissues. The inorganic divalent cation can, in turn, be reduced to