• Clinical science

Metal toxicity

Abstract

Exposure to toxic amounts of heavy metals such as mercury, lead, chrome, and cadmium can be harmful to the human body, potentially causing both acute symptoms (e.g., local irritation, gastroenteritis, and pneumonia) and long‑term effects (e.g., abnormal physical development, cancer, damage to central nervous system, and kidney). Toxic metals have many industrial purposes and therefore represent occupational hazards for a number of professions. Industrial pollution with heavy metals can affect the wider population through the contamination of food (e.g., mercury in fish) and water (e.g., lead, arsenic).

General considerations

  • Chronic exposure to heavy metals generally manifests first as CNS and kidney damage.
  • For chronic diseases resulting from the inhalation of metal dust, see pneumoconiosis.

Overview of principal metal toxicities

Signs and Symptoms Diagnosis Further information Treatment
Arsenic
  • Severe intoxication may cause garlic‑like odor
  • Dimercaprol
  • Dimercaptosuccinic acid (succimer): more commonly used in children
Lead
  • Intestinal colic (lead colic)
  • Purple-bluish line on the gums (lead line or Burton line)
  • Paralysis of the radial or peroneal nerve (wrist/foot drop)
  • Symptoms of anemia
  • Nephropathy
  • Encephalopathy, cognitive impairment
  • Detectable in blood
  • Succimer (Dimercaptosuccinic acid, DMSA)
  • Dimercaprol and/or calcium disodium edetate (CaNa2EDTA)
  • D‑penicillamine: used as third-line drug in children
Cadmium
  • Chronic exposure causes Itai‑itai disease
  • No known antidote
Chromium
  • Detectable in blood and urine
  • Carcinogenic
  • None (induction of vomiting is contraindicated because of its corrosiveness)
Iron
  • Hemorrhagic gastroenteritis, shock symptoms
  • Neuro- and nephrotoxicity, respiratory depression
  • Clinical
  • Common in pediatric care
  • Deferoxamine
Mercury
  • Blue-violet discoloration along the margins of the gums
  • D‑penicillamine
Thallium
  • White bands across the nails (Mees's lines)
  • Hair loss
  • Detectable in blood and urine
  • Highly toxic
  • Survivors often develop ocular or neurologic sequelae
  • Prussian blue
Vanadium
  • Greenish‑black coloration of the tongue
  • Detectable in blood and urine
  • None

References:[1][2][3][4]

Arsenic

  • Sources of exposure
    • Metal smelting; , pesticides, herbicides, contaminated water (esp. in developing countries), ore mining, semiconductor production, paint and glass manufacturing
  • Pathophysiology: has direct toxic effects on endothelial cells; induces oxidative stress, and disrupts ATP production
  • Clinical features
  • Diagnosis: urinalysis
  • Treatment
    • Consider gastric lavage, activated carbon in acute toxicity
    • Antidote: dimercaprol, succimer (in children)

References:[2][3][4][5]

Lead

  • Sources of exposure
    • Battery manufacturing, metallurgy, corrosion inhibition
    • Gun range
    • Tableware containing lead
    • Drinking water (from lead plumbing or contaminated sources )
    • Antique or imported toys painted with lead-containing paint
  • Action: heme synthesis disruption via inhibition of aminolevulinate dehydratase (catalyzes the conversion of aminolevulinic acid to porphobilinogen)
  • Clinical features
  • Diagnosis
    • Blood lead level (BLL) measurement
    • Basophilic stippling of erythrocytes on peripheral blood smear
    • Microcytic, hypochromic anemia
    • Imaging (not routinely indicated): lead flecks on abdominal x-ray, lead lines on long-bone x-rays
    • Inspection of the patient's environment for lead sources to prevent further exposure
  • Screening in high-risk pediatric populations
    • Living in older housing under renovation or with peeling paint
    • Sibling or playmate with lead poisoning
    • Recent immigrant, refugee, or foreign adoptee
    • History of pica
  • Treatment
    • Decrease exposure: professional lead paint abatement, dust reduction, minimization of contact with bare soil
    • Nutrition: Calcium, iron, zinc, and vitamins C and D-rich diet
    • Chelation therapy indications:
      • Oral succimer with/without intravenous or intramuscular CaNa2EDTA (Calcium disodium ethylenediamine tetraacetic acid) and D-penicillamine
        • Children with BLL ≥ 45 μg/dl
        • Asymptomatic adults with BLL ≥ 80 μg/dl
        • Symptomatic adults with BLL ≥ 50 μg/dl
      • IM dimercaprol; (British antilewisite, BAL) with/without CaNa2EDTA
        • Patients with lead encephalopathy
        • BLL ≥ 70 μg/dl

ABCDEFGH – Anemia, Basophilic stripping, Colic, Diarrhea, Encephalopathy, Foot drop, Gum deposition/Growth retardation/Gout, Hyperuricemia/Hypertension


References:[6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]

Cadmium

References:[21][22][23]

Iron

  • Definition: chemical element often used as supplement in pediatrics and prenatal care and in the management of anemia
  • Epidemiology: toxicity is common in pediatric care (ingestion of red iron tablets mistaken for candy)
  • Effect: corrosive and toxic effects on cells
  • Clinical features
    • Initially hemorrhagic gastroenteritis, shock symptoms
    • In case patient survives: symptom-free interval after 6 hours
    • Causes dark-colored stools
    • Later: risk of renal and liver failure, unconsciousness, and respiratory depression
  • Diagnostics: anion gap metabolic acidosis
  • Antidote: deferoxamine

References:[24]

Mercury

  • Sources of exposure
    • Organometallic methylmercury in fish
    • Inorganic, metallic mercury in thermometers, amalgam (dental fillings), pyrotechnics, and metal working
  • Clinical features
  • Diagnosis
  • Treatment
    • D‑penicillamine
  • Antidote
    • 2,3‑dimercaptosuccinic acid
    • Dimercaprol

References:[25][26][27][28][29]

Thallium

  • Sources of exposure
    • Glass industry
    • Rat poison
  • Clinical features
  • Diagnosis: present in blood and/or urine

Manganese

Nickel

  • Sources of exposure: alloys (e.g., in coins, jewelry)
  • Clinical features

Chromium

  • Sources of exposure
    • Galvanization (chrome plating), paint and glass manufacturing, tanning leather, building materials (potassium dichromate in cement → “cement eczema” is an occupational hazard among construction workers)
  • Action
    • Corrosive
    • Allergenic
  • Clinical features
  • Diagnosis: urine or blood

Platinum

Vanadium (vanadium pentoxide)