Mercury Exposure

Mercury 101 - Element Exposed

Key forms of Mercury ($Hg$) with their sources and properties:

Body Invader - Toxic Trail

• Absorption:
  • Elemental ($Hg^0$): Primarily via inhalation (efficient).
  • Inorganic ($Hg^{2+}$) & Organic ($MeHg$): Gastrointestinal tract.
• Distribution: Systemic; readily crosses blood-brain and placental barriers.
  • Targets: Brain (CNS), kidneys.
  • Accumulates: Placenta, breast milk ($MeHg$).
• Metabolism:
  • $Hg^0$ oxidized to $Hg^{2+}$ in blood/tissues.
  • $MeHg$ slowly demethylated to inorganic $Hg^{2+}$.
• Excretion:
  • Urine: Predominantly $Hg^0$ and $Hg^{2+}$.
  • Feces: Mainly $MeHg$ and some $Hg^{2+}$.
  • Hair: $MeHg$ (reflects chronic exposure).

Mechanism of Toxicity:

• High affinity for sulfhydryl (-SH) groups.
• Leads to enzyme inhibition & oxidative stress.
• Disrupts neurotransmission; damages microtubules.

⭐ Elemental mercury vapor is well-absorbed via inhalation (≈80%) and primarily targets the CNS and kidneys.

Poison's Portrait - Symptoms Spotlight

Manifestations depend on mercury form and exposure (acute/chronic).

• Elemental ($Hg^0$ vapor)

  • Acute: Pneumonitis.
  • Chronic: Tremors, erethism ("Mad Hatter's").

• Inorganic ($Hg^{2+}$ salts)

  • Acute: Hemorrhagic gastroenteritis, renal (ATN).
  • Chronic: Gingivostomatitis, nephropathy.

• Organic ($CH_3Hg^+$ - Methylmercury)

  • CNS: Paresthesias, ataxia, visual field constriction, hearing loss. Minamata disease.
  • Children: Developmental delay.

• Pediatric Hallmark: Acrodynia (Pink Disease)

  • Chronic exposure (often inorganic $Hg$).
  • Features: Painful, pink hands/feet, hypertension, photophobia, irritability, sweating.
  • 📌 Mnemonic: PINK - Pain, Irritability/Insomnia, Neuropathy, K(C)ats (hypertension), Sweating/Skin changes.

⭐ Acrodynia, or Pink Disease, characterized by painful, swollen, pink hands and feet, is a distinctive feature of chronic mercury poisoning in young children.

Detect & Defend - Healing Hands

• Diagnosis:
  • History of exposure (dietary, environmental, occupational).
  • Lab tests:
    • Blood mercury: Acute/recent high exposure (concern > 5-10 µg/L).
    • 24-hr urine mercury: Best for inorganic/elemental mercury.
    • Hair mercury: Chronic organic (esp. methylmercury) exposure.
  • Neuropsychological testing: Assess cognitive, motor, behavioral effects.
• Management:
  • Crucial first step: Stop further exposure.
  • Supportive care: Maintain vital functions, hydration, nutrition.
  • Decontamination: E.g., activated charcoal for recent significant ingestion.
  • Chelation Therapy:
    • Agents: Succimer (DMSA), Dimercaprol (BAL), DMPS.
    • Indications: Symptomatic patients, very high mercury levels. Note side effects.

    ⭐ Succimer (DMSA) is the preferred oral chelating agent for pediatric mercury poisoning, particularly for inorganic and elemental forms.

• Prevention:
  • Avoid high-mercury fish (shark, swordfish).
  • Proper disposal of mercury-containing items (thermometers, batteries).
  • Awareness campaigns. Maternal counseling on safe fish consumption.

, Dimercaprol (BAL), DMPS - with indications, contraindications, and key side effects)

High‑Yield Points - ⚡ Biggest Takeaways

• Methylmercury from fish consumption is a potent neurotoxin, especially impacting the developing brain.
• Minamata disease (severe methylmercury poisoning) features cerebellar ataxia, dysarthria, and visual field constriction.
• Acrodynia (Pink Disease): hypersensitivity to inorganic mercury causing painful, pink extremities, rash, and photophobia/irritability.
• Diagnosis: Blood and urine mercury levels are key; hair analysis for chronic methylmercury.
• Treatment: Chelation therapy (DMSA, DMPS) and immediate removal from exposure source.
• Elemental mercury (e.g., broken thermometers) primarily causes respiratory distress and neurological symptoms if inhaled.