Mercury toxicity Domina Petric, MD

Mercury Mercury (quicksilver) is the only metal that is liquid under ordinary conditions. Japanese fishing village of Minamata (1950s): birth defects and neurologic diseases caused by methylmercury in contaminated seafood (industrial discharges into the bay from a nearby factory).

Mercury HgS in cinnabar. electrolytic production of chlorine and caustic soda electrical equipment thermometers fluorescent lamps dental amalgam artisanal gold antiseptics Thimerosal has been removed from almost all the vaccines. Environmental exposure to mercury from the burning of fossil fuels and the bioaccumulation of methylmercury in fish is still very important problem worldwide.

Pharmacokinetics Elemental mercury is quite volatile and can be absorbed from the lungs. It is poorly absorbed from the intact gastrointestinal tract. Inhaled mercury is the primary source of occupational exposure.

Pharmacokinetics Organic short-chain alkylmercury compounds are volatile and potentially harmful by inhalation and ingestion. Percutaneous absorption of metallic mercury and inorganic mercury can be of clinical concern following massive acute or long-term chronic exposure.

Pharmacokinetics Alkylmercury compounds are well absorbed through the skin. Acute contact with a few drops of dimethylmercury has resulted in severe, delayed toxicity.

Pharmacokinetics After absorption, mercury is distributed to the tissues within a few hours. The highest concentration is in the kidney.

Pharmacokinetics Inorganic mercury is excreted through the urine and feces. Most of the inorganic mercury is excreted within weeks to months, but a fraction may be retained in the kidneys and brain for years.

Pharmacokinetics After inhalation of elemental mercury vapor, urinary mercury levels decline with a half-life 1-3 months. Methylmercury has a blood and whole body half-life 50 days. Methylmercury undergoes biliary excretion and enterohepatic circulation. 2/3 of methylmercury is excreted in the feces.

Pharmacokinetics Mercury binds to sulfhydryl groups in keratinized tissue so traces may appear in the hair and nails.

Mercury interacts with sulfhydryl groups. Mercury intoxication Mercury interacts with sulfhydryl groups. It inhibits enzymes and alterates cell membranes.

Acute mercury intoxication Acute inhalation of elemental mercury vapors may cause chemical pneumonitis and noncardiogenic pulmonary oedema. Acute gingivostomatitis may occur. Neurologic sequelae!

Acute mercury intoxication Acute ingestion of inorganic mercury salts (mercuric chloride) can ressult in a corrosive, potentially life-threatening hemorrhagic gastroenteritis. After hours to days acute tubular necrosis and oliguric renal failure occur.

Treatment Intensive supportive care! Prompt chelation with oral or intravenous unithiol, intramuscular dimercaprol or oral succimer diminishes nephrotoxicity after acute exposure to inorganic mercury salts.

Treatment Vigorous hydration may help to maintain urine output. If acute renal failure ensues, days to weeks of hemodialysis or hemodiafiltration in conjunction with chelation may be necessary.

Chronic mercury intoxication Chronic poisoning from inhalation of mercury vapor results in a classic triad: TREMOR NEUROPSYCHIATRIC DISTURBANCE GINGIVOSTOMATITIS

Chronic mercury intoxication Tremor usually begins as a fine intention tremor of the hands. The face may also be involved. Progression to choreiform movements of the limbs may occur.

Chronic mercury intoxication Neuropsychiatric manifestations: memory loss fatigue insomnia anorexia

Chronic mercury intoxication Erethism is a behavioral pattern that includes: insidious change in mood shyness, withdrawal, depression explosive anger or blushing

Chronic mercury intoxication Low-dose exposure may produce subclinical neurologic effects. Gingivostomatitis, sometimes with loosening of the teeth, may be reported after high-dose exposure.

Chronic mercury intoxication Overt peripheral neuropathy is rare. Evidence of peripheral nerve damage may be detected on electrodiagnostic testing.

Chronic mercury intoxication Acrodynia is an uncommon idiosyncratic reaction to subacute or chronic mercury exposure (mainly in children). It is characterized by painful erythema of the extremities. It may be associated with hypertension, diaphoresis, anorexia, insomnia, irritability, apathy and miliary rash.

https://www.researchgate.net (Deniz Yeter publication)

Chronic mercury intoxication Chronic exposure to inorganic mercury salts (via topical application in cosmetic creams) has been associated with neurological symptoms and renal toxicity.

Chronic mercury intoxication Methylmercury intoxication affects mainly the central nervous system: paresthesias, ataxia hearing impairment dysarthria progressive constriction of the visual fields

Chronic mercury intoxication Signs and symptoms of methylmercury intoxication may first appear several weeks or months after exposure begins.

Chronic mercury intoxication Methylmercury is a reproductive toxin. High-dose prenatal exposure to methylmercury may produce mental retardation and a cerebral palsy-like syndrome in the offspring.

Chronic mercury intoxication Low-level prenatal exposures to methylmercury have been associated with a risk of subclinical neurodevelopmental deficits.

Chronic mercury intoxication Dimethylmercury is a rarely encountered, but extremely neurotoxic form of organomercury. It may be lethal in small quantities.

Diagnosis history physical findings confirmatory laboratory testing The urine mercury concentration should be <5 mcg/L and whole blood mercury conc. <5 mcg/L.

End-of-work-week whole blood mercury concetrations less than 15 mcg/L. Prevention Workplace exposures should result in urinary mercury concentrations <35 mcg per gram of creatinine. End-of-work-week whole blood mercury concetrations less than 15 mcg/L.

Prevention Pregnant women, nursing mothers and young children should avoid consumption of fish with high mercury levels (swordfish) and limit consumption of fish with lower levels of mercury, to no more than 12 ounces (340 g) per week.

Treatment Succimer, unithiol and N-acetyl-L-cysteine (NAC) may enchance body clearance of methylmercury.

Treatment Dimercaprol should not be used in treatment of exposure to elemental or organic mercury. Dimercaprol redistributes mercury to the central nervous system from other tissue sites.

Literature Katzung, Masters, Trevor. Basic and clinical pharmacology. www.researchgate.net