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

MERCURY 171
2. HEALTH EFFECTS
declined (no reason provided). Other sources of mercury could have caused the increase, so little can be
concluded about how much of the subcutaneous liquid mercury entered the systemic circulation.
In a much more informative case history, a 19-year-old man had injected mercury subcutaneously
(Bradberry et al. 1996). Blood and urine mercury concentrations were followed for 6 years after
presentation. Hematological and biochemical profiles were normal. Histological results indicated a chronic
inflammatory reaction with granuloma formation, secondary to the globular mercury. A postoperative Xray
of the elbow indicated persistent subcutaneous mercury particles. Apart from the initial local
discomfort, the patient remained asymptomatic and clinical examination revealed no abnormality up to
6 years postsurgery. No systemic features of mercury poisoning were evident. Blood mercury levels
declined from 60 to 70 µg/L at 1 year postoperation to 10 µg/L at 6 years. Serial sampling results of total
mercury in 24 urine collections indicated peaks up to 1.2 mg during the first year postoperation, which
declined to 59 µg/L at 6 years. The elevated blood and urine levels indicate some systemic absorption. The
effects of the surgery on migration of mercury from the subcutaneous tissue to the systemic circulation are
not known.
2.3.2 Distribution
In humans, metallic mercury is distributed throughout the body following inhalation exposure. It can
readily cross the blood-brain and placental barriers because of its high lipophilicity. After oxidation to
mercuric mercury, it accumulates primarily in the kidneys. Inorganic divalent mercury compounds
similarly reach all organs; however, the extent of accumulation in the brain and fetus is lower than metallic
mercury because of the lower lipophilicity of inorganic mercury compounds. Organic mercury compounds
distribute throughout the body following oral exposure and have the highest accumulation in the kidneys.
As with metallic mercury, the ability of methyl- and phenyl mercury compounds to cross the blood-brain
and placental barriers allows distribution, and subsequent accumulation, in the brain and fetus.
2.3.2.1 Inhalation Exposure
Metallic Mercury. The lipophilic nature of metallic mercury results in its distribution throughout the body.
Metallic mercury in solution in the body is highly lipophilic, thereby allowing it to cross blood-brain and
placental barriers with ease (Clarkson 1989). Mercury distributes to all tissues and reaches peak levels
within 24 hours, except in the brain where peak levels are achieved within 2–3 days (Hursh et al. 1976).