Heavy Metal Poisoning by arsenic, cadmium, lead and mercury has been already discussed. Here we will discus about heavy metal poisoning by uncommon poisoning by heavy metals. Uncommon heavy metal poisoning includes poisoning by aluminum, chromium, cobalt, manganese, nickel, selenium, thallium, tin etc. The poisoning due to the above mentioned heavy metals is relatively rare and there is uncertainty regarding their potential toxicities.
It can cause encephalopathy in patients with severe renal disease who are undergoing dialysis. High levels of aluminum are found in the cerebral cortex and hippocampus of patients with Alzheimer’s disease. High levels of aluminum are also found in the drinking water and soil of areas with a high incidence of Alzheimer’s disease. But it cannot be proved that aluminum is the causative factor or contributing factor in the development of Alzheimer’s disease.
It is a corrosive. Workers of chromate and chrome pigment production industries have a greater risk of lung cancer due to chronic exposure to chromium. Hexavalent chromium is mainly responsible.
cobalt chloride was once used as fortifier of beer which led to outbreaks of fatal cardiomyopathy among heavy consumers. Now it is no more used and there are very rare incidences of cobalt poisoning due to it.
Chronic exposure to manganese can cause Parkinsonian syndrome. Parkinsonian syndrome is seen in persons like miners, dry-battery manufacturers, and arc welders. It is seen within 1–2 years of occupational exposure. Gait disorders, postural instability, tremor, expressionless face and psychiatric symptoms can be seen.
Nickel exposure can cause allergic reaction and chronic exposure by inhalation of nickel compounds with low aqueous solubility like nickel subsulfide and nickel oxide in occupational settings can cause is an increased risk of lung cancer.
Overexposure to selenium can cause local irritation of the respiratory system, gastrointestinal irritation and eyes, hepatitis, loss of hair, depigmentation, and peripheral nerve damage.
Thallium can be absorbed through ingestion, inhalation and also through skin. Thallium is used in insecticides, metal alloys, and fireworks. Severe poisoning occurs after a single ingested dose of more than 1g or more than 8 mg/kg. Nausea and vomiting, abdominal pain, and blood in vomit occur before confusion, psychosis and coma.
Asbestos is absorbed through inhalation. Asbestos was used in building insulation through the late 1970’s. Asbestos is the leading cause of mesothelioma, a rare form of cancer that develops from the cells of the mesothelium.
The principle of treatment is same like other heavy metal poisoning. Chelating agents and symptomatic treatment should be given. Gastric lavage (removing stomach contents) can be done if poisoning is by ingestion. Being metal all are radio opaque and X-ray helps in diagnosis and extent of heavy metal in stomach.
In thallium poisoning Prussian blue prevents absorption and is given orally at 250 mg/kg in divided doses. Thallium poisoning may be less severe when activated charcoal is used to interrupt its enterohepatic circulation (liver and intestinal circulation of poison). Other measures include forced diuresis, treatment with potassium chloride to promote renal excretion of thallium, and peritoneal dialysis.
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Sign & Symptoms of Mercury Poisoning: Chronic exposure to metallic mercury vapor produces characteristic intension tremor. It can also produce Mercurial erethism (excitability, insomnia, timidity, memory loss, and delirium known as “mad as a hatter”). Decreased motor speed, visual scanning, and decreased verbal and visual memory, visuomotor (visual & motor) coordination are seen on neurobehavioral tests. Toxicity from elemental or inorganic mercury exposure begins when blood level is more than 3.6 µg/100 ml and urine levels more than 15µg/100 ml.
Organic mercury exposure is measured by mercury levels in blood in acute poisoning and mercury levels in hair in chronic poisoning.
If children are exposed to mercury in any form (organic, inorganic, vaporized or ingested) may develop acrodynia known as “pink disease” that include flushing, itching, swelling, irritability, hypertension, high pulse rate, excessive salivation, perspiration, weakness, morbilliform rashes, desquamation of palms and soles.
Treatment: Acute ingestion of mercury is treated by gastric lavage or by inducing vomiting (with gag reflex which is by touching the pharynx or by hypertonic saline or drugs that cause vomiting). Polythiol resin is given which binds to mercury in the gastrointestinal tract (GIT) and reduce absorption from GIT. Chelating agent (bind metals into stable cyclic compounds with relatively low toxicity and enhances their excretion) like dimercaprol (British Anti Lewisite or BAL), 24 mg/kg per day IM in divided doses, penicillamine or DMSA (succimer or dimercaptosuccinic acid) should be given. Chelating agents are given as several 5 day courses which are separated by few days of rest days. If renal failure develops, treat with hemodialysis or peritoneal dialysis.
Chronic inorganic mercury poisoning is treated with N-acetyl penicillamine.
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