TABLE 2-2 Summary Table Comparing Toxicologically Relevant Mercury Species

Methylmercury (CH3Hg+)

Elemental Mercury (Hg0)

Mercuric Mercury (Hg2+)

Sources of Exposure


Fish, marine mammals, crustaceans, animals and poultry fed fish meal

Dental amalgams, occupational exposure, Caribbean religious ceremonies, fossil fuels, incinerators

Oxidation of elemental mercury or demethylation of MeHg; deliberate or accidental poisoning with HgCl2

Biological Monitoring


Hair, blood, cord blood

Urine, blood

Urine, blood





Inhalation: Vapors of MeHg absorbed

Inhalation: Approximately 80% of inhaled dose of Hg0 readily absorbed

Inhalation: Aerosols of HgCl2 absorbed

Oral: Approximately 95% of MeHg in fish readily absorbed from GI tract

Oral: GI absorption of metallic Hg is poor; any released vapor in GI tract converted to mercuric sulfide and excreted

Oral; 7-15% of ingested dose of HgCl2 absorbed from the GI tract; absorption proportional to water solubility of mercuric salt; uptake by neonates greater than adults

Dermal: In guinea pigs, 3-5% of applied dose absorbed in 5 hr

Dermal: Average rate of absorption of Hg0 through human skin, 0.024 ng/cm2 for every 1 mg/m3 in air

Dermal: In guinea pigs, 2-3% of applied dose of HgCl2 absorbed



Distributed throughout body since lipophilic; approximately 1-10% of absorbed oral dose of MeHg distributed to blood; 90% of blood MeHg in RBCs

Rapidly distributed throughout the body since it is lipophilic

Highest accumulation in kidney; fraction of dose retained in kidney dose dependent

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