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

MERCURY 125
2. HEALTH EFFECTS
forgetfulness, irritability, and fatigue. The occupational exposures made it difficult to determine any
additional neurological effects from the acute exposure. There was no history of peripheral neuropathy,
vertigo, insomnia, or muscular weakness. Neuropsychiatric and psychology evaluations indicated poor
concentration and a defect in recent memory. EEG results indicated diffuse cortical dysfunction
predominantly on the left hemisphere. He was treated with immediate gastric lavage and cathartics. He
also received D-penicillamine 1 g/day orally for 7 days. Blood and urine mercury levels obtained 3 days
after chelating therapy were 116.9 and 22.9µg/L, respectively. By 2 weeks postexposure, most of the
mercury had been excreted in the feces and was measured at a total volume of 220 mL (this number was
used to estimate the amount initially ingested). The patient was lost to follow-up, but returned to the
hospital 6 months later (for glycemic control), at which time examination revealed a lessening of his hand
tremors.
Most case studies of neurotoxicity in humans induced by oral exposure to inorganic mercury salts have
reported neurotoxic effects as the result of ingestion of therapeutic agents that contain mercurous chloride
(e.g., teething powders, ointments, and laxatives). Several children treated with tablets or powders
containing mercurous chloride exhibited irritability, fretfulness, sleeplessness, weakness, photophobia,
muscle twitching, hyperactive or hypoactive tendon reflexes, and/or confusion (Warkany and Hubbard
1953). A 4-year-old boy who had been given a Chinese medicine containing mercurous chloride for
3 months developed drooling, dysphagia, irregular arm movements, and impaired gait (Kang-Yum and
Oransky 1992). Davis et al. (1974) reported that two women developed dementia and irritability due to
chronic ingestion of a tablet laxative that contained 120 mg of USP-grade mercurous chloride (0.72 mg
Hg/kg/day, assuming an average body weight of 70 kg). One woman had taken 2 tablets daily for 25 years,
and the other woman took 2 tablets daily for 6 years. Both patients died from inorganic mercury poisoning,
and at autopsy, low brain weight and volume and a reduced number of nerve cells in the cerebellum were
seen. Light microscopic analysis revealed granules of mercury within neuronal cytoplasm. Electron
microscopy revealed mercury deposits in some neurons.
In addition, neurotoxicity has been observed after ingestion of lethal doses of mercuric chloride. Blurred
vision and diplopia were reported by a 35-year-old man who ingested a lethal dose of mercuric chloride
(Murphy et al. 1979). Prior to death, the man experienced repeated seizures. An autopsy revealed
abscesses on the occipital lobe and cerebellum.