Heavy Metal Toxicity Notes

Heavy Metal Toxicity

• Routes of Exposure: Any route is possible.
• Metallic Taste: Characteristic of arsenic poisoning.
• Local Effects:
  • Irritation.
  • Gastrointestinal tract issues (Nausea, Vomiting, Diarrhea) - e.g., lead poisoning often causes constipation.
• Specific Organ Effects:
  • Mercury: Primarily affects the kidneys.
  • Iron: Primarily affects the liver.
  • Arsenic: Affects the liver, heart, kidneys, and skin.
  • Lead: Affects the Blood-Brain Barrier (BBB) and Peripheral Nerves (PN).
• Investigations:
  • Reinsch test.
  • X-ray.
  • Atomic absorption.
• Treatment (TTT):
  • Supportive care.
  • Gastric lavage.
  • Chelators.
  • Activated Charcoal (AC) - questionable efficacy.
• General Characteristics: (of heavy metal toxicity)

Reinsch Test: Detecting Heavy Metals

• Classical Definition: A presumptive test to indicate the presence of heavy metals in biological samples.
• Principle: Based on the electrochemical displacement of copper by other metals.
  • Elements below copper in the electrochemical series will displace it.
• Procedure: Antimony, arsenic, bismuth, and mercury will deposit on a copper wire or strip.
  • Discoloration of the copper indicates a positive result.

Sublimation

• Definition: The transition of a substance from a solid state to a gas state without passing through a liquid state.
• Precautions for Sublimation:
  1. Use a dry and clean sublimation tube.
  2. Apply a weak and blue flame.
  3. Heat the base of the tube only.
  4. Incline the tube at a 45-degree angle.
  5. Ensure the tube opening does not face anyone.

Advantages and Disadvantages of Reinsch Test

• Advantages:
  • Rapid screening test.
  • Sensitive.
  • Reliable.
  • Can be used on biological fluids or tissue homogenates without extensive preliminary treatment.
  • Sensitivity levels:
    • Arsenic: $0.5 \, mg/L$
    • Antimony and Bismuth: $1.0 \, mg/L$
    • Mercury: $2.5 \, mg/L$
• Disadvantages:
  • Qualitative test only (not quantitative).
  • Cannot differentiate between acute and chronic poisoning.

Reagents Used in Reinsch Test

• Hydrochloric acid (HCl): both diluted and pure forms.
• Water ($H_2O$) : added before HCl.
• Decantation.
• Descending of copper foil (Cu).
• Drying.

Identification of Mercury and Arsenic using Sublimation in Reinsch Test

• Mercury (Hg):
  • Sublimation yields black spherical globules of various sizes.
  • Reagent used: Hydrochloric acid.
• Arsenic (As):
  • Sublimation yields Tetrahedral & octahedral crystals of variable sizes.
  • Reagent used: Hydrochloric acid.

Confirmatory Tests for Heavy Metal Detection

1. Atomic Absorption Spectrophotometry
2. Gas Chromatography (GC)
3. Liquid Chromatography
4. High-Performance Liquid Chromatography (HPLC)

Lead Toxicity and Lead Lines

• X-ray of knee joint, hand, and wrist can show lead lines in cases of lead toxicity.
• Lead lines visible in bones of lead-poisoned individuals.

Chelators for Heavy Metal Toxicity