Selenium Toxicity

Aka: Selenium Toxicity, Selenious Acid Toxicity, Selenium Poisoning, Selenium Overdose, Gun Blue Ingestion, Selenosis

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II. Background

  1. Selenium is an essential trace element in humans
    1. Optimal specific enzyme function requires 55 mcg/day
    2. Examples of enzymes dependent on Selenium
      1. Glutathione peroxidase (neutralizes peroxides, reduces oxidative stress)
      2. Iodothyronine-5-deiodinase (converts Thyroid Hormone T4 to the active T3 form)
  2. Selenious Acid is an acidic compound of the element Selenium
    1. Analogous to sulfur in sulfuric Acid (H2SO3), Selenium is the key element in Selenious Acid (H2SeO3)
    2. Selenious Acid forms when Selenium dioxide is added to water
  3. Selenious Acid Industrial Uses (esp. metallurgy, e.g. Gun Blue)
    1. Xerography and Photography (Selenium has photovoltaic and photoconductive properties)
    2. Tints the color of steel to blue (used especially in firearm manufacturing)
    3. Also used to modify the color of other metals (e.g. Copper, brass)
  4. Selenious Acid contains very high Selenium concentrations that may be lethal even in small ingestions
    1. Contrast with the trace quantities of Selenium when taken in Vitamins

III. Causes: Exposures

  1. Elemental Selenium (chronic Selenium Toxicity)
    1. Photography
    2. Copper refining
    3. Foods
      1. Tuna
      2. Oysters
      3. Brazil nuts
  2. Selenite Salts (SeO2, SeOCl2, acute Selenium Toxicity)
    1. Glass decolorizer
    2. Plasticizer
    3. Rubber Vulcanization
  3. Selenious acid (acute Selenium Toxicity)
    1. Metallurgy (e.g. Gun Blue)

IV. Mechanism

  1. Electrophilic selenide anions
    1. Increase reactive oxygen species
  2. Sulhydryl-containing enzymes are inhibited by selenious acid
  3. Corrosive Acid (Selenious Acid)
    1. See Caustic Ingestion

V. Pharmacokinetics

  1. Severe, life threatening toxicity occurs even with low dose ingestions <1 mg/kg
  2. Fatal doses with ingestion of >10 mg/kg selenious acid or >66 mg/kg Sodium selenite
  3. Absorption via ingestion or via skin contact
    1. Highest Bioavailability with selenious acid and organoselenium compounds
  4. Inhalation may cause pneumonitis
  5. Half-Life: Days
  6. Excretion
    1. Methylselenides are eliminated in the urine and in the breath (Garlic odor)

VI. Adverse Effects: Acute Toxicity

  1. Occurs with Selenite Salts or Selenious acid exposure (not with Elemental Selenium exposure)
  2. Gastrointestinal
    1. Nausea or Vomiting
    2. Abdominal Pain
    3. Foul Garlic odor to the breath
    4. Diarrhea
    5. Mucosal burns
    6. Hemorrhagic Gastritis
  3. Muscular
    1. Muscle Weakness
    2. Acute Respiratory Failure (Bellows Failure)
    3. Muscle Fasciculations
    4. Myoclonus
    5. Rhabdomyolysis
  4. Cardiac
    1. Chest Pain
    2. Hypotension (due to Vasoplegia, myocardial depression)
    3. EKG Abnormalities
      1. QTc Prolongation
      2. Ventricular Dysrhythmia
  5. Respiratory
    1. Dyspnea
    2. Hypoxia
    3. Edema
  6. Skin and Mucous Membranes (Selenious acid)
    1. Caustic burns
    2. Conjunctival edema
    3. Corneal Injury

VII. Adverse Effects: Chronic Toxicity (Selenosis)

  1. Chronic toxicity (Selenosis) may occur with longterm over-exposure to Elemental Selenium
  2. Dermatologic
    1. Painful skin lesions
    2. Brittle Nails
    3. Alopecia
  3. Neurologic
    1. Irritability
    2. Fatigue
    3. Memory Loss

VIII. Labs

  1. Complete Blood Count
  2. Comprehensive metabolic panel
  3. Thyroid Stimulating Hormone
  4. Selenium level
    1. Acute toxicity: Serum Selenium level (and/or urine Selenium level)
    2. Chronic toxicity: Whole blood Selenium level
  5. Other Acute Poisoning labs (e.g. Acetaminophen level, Pregnancy Test)
    1. See Unknown Ingestion

IX. Management: Acute Toxicity

  1. Decontamination
    1. Skin Decontamination
    2. Gastrointestinal Decontamination
      1. Consider nasogastric lavage or Activated Charcoal for recent ingestion
  2. Supportive Care
    1. No specific antidotes
    2. Intravenous Fluids
    3. Vasopressors for refractory shock
  3. Endoscopy
    1. Gastrointestinal Hemorrhage and other complications
  4. Other measures to consider (unclear benefit)
    1. Chelation therapy (dimercaprol or CalciumSodium EDTA)
    2. Hemodialysis
  5. Disposition
    1. Admit all symptomatic inorganic Selenium ingestions and exposures (Selenite Salts, Selenious acid)
    2. Indications for home disposition
      1. No symptoms (including gastrointestinal) at 6 hours after exposure OR
      2. Elemental Selenium exposure (no acute toxicity, only chronic toxicity risk)

X. References

  1. Carroll and Yakey (2026) Crit Dec Emerg Med 40(7): 36
  2. Tomaszewski (2023) Crit Dec Emerg Med 37(7): 32
  3. Nuttall (2006) Ann Clin Lab Sci 36(4): 409-20
    1. http://www.annclinlabsci.org/content/36/4/409.long

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