Pesticide Exposure

Pesticide Basics - Chemical Culprits

• Definition: Agents to control pests (insects, rodents, fungi, weeds).
• Major Classes:
  • Organophosphates (OPs): Malathion, Parathion. Highly toxic.
  • Carbamates: Carbaryl, Aldicarb. Similar to OPs, shorter action.
  • Organochlorines (OCs): DDT, Endosulfan. Historically significant but now heavily restricted/banned in India due to persistence and bioaccumulation.
  • Pyrethroids: Cypermethrin, Deltamethrin. Synthetic, lower human toxicity.
  • Rodenticides: Aluminium Phosphide (Celphos), Zinc Phosphide.
  • Herbicides: Paraquat, Glyphosate.

⭐ Recent data (2023-2024) indicates ingestion of insecticides (often OPs or Aluminium Phosphide) remains the most common route of fatal poisoning in India, investigated under BNS provisions.

OPs & Carbamates - Cholinergic Chaos

OPs & Carbamates inhibit Acetylcholinesterase (AChE) → ↑ Acetylcholine (ACh) → cholinergic crisis.

• Mechanism:
  • OPs: Irreversible AChE inhibition ("aging").
  • Carbamates: Reversible AChE inhibition.
• Clinical Features:
  • Muscarinic: 📌 DUMBELS (Diarrhea, Urination, Miosis, Bronchorrhea/Bronchospasm, Emesis, Lacrimation, Salivation).
  • Nicotinic: Fasciculations, weakness, paralysis, HTN, tachycardia.
  • CNS: Confusion, seizures, coma.
• Diagnosis: Clinical; ↓ RBC/plasma cholinesterase; Atropine challenge.
• Management:
  • ABCs, Decontamination.
  • Atropine: 1-2 mg IV, doubling every 3-5 min till atropinization (clearing secretions, HR >80 bpm, pupils no longer miotic).
  • Pralidoxime (PAM): OPs only. 30 mg/kg IV bolus, then 8-10 mg/kg/hour infusion.

  ⭐ Pralidoxime (PAM) effectiveness can extend beyond 48 hours in OP poisoning, especially with newer compounds. Early administration is crucial, but the therapeutic window may be longer than traditionally thought.

  • Diazepam for seizures.

OCs & Pyrethroids - Nerve Disruptors

• Organochlorines (OCs):
  • Mechanism: Delay Na+ channel inactivation & K+ channel opening in axons.
  • Effects: CNS stimulants (tremors, paresthesia, convulsions).
  • Examples: DDT, Lindane (HCH), Endosulfan.

  • ⭐ Organochlorines are known for bioaccumulation and persistence in the environment and body fat.

• Pyrethroids:
  • Mechanism: Prolong Na+ channel opening. Type II also inhibit GABA-gated Cl- channels.
  • Type I (T-syndrome): Tremors. E.g., Allethrin, Permethrin.
  • Type II (CS-syndrome): Choreoathetosis, Salivation. E.g., Cypermethrin, Deltamethrin. (📌 CS for Cypermethrin, Cl- channels)
  • Features: Rapidly metabolized; allergic dermatitis, asthma.
• Organophosphates (OPs):
  • Mechanism: Irreversible acetylcholinesterase inhibition causing acetylcholine accumulation.
  • Effects: Cholinergic crisis, status epilepticus, potential death.

  • ⭐ Major cause of pesticide poisoning globally, especially in self-harm cases under BNS provisions for suicide attempts.

Metallic & Others - Deadly Dusts & Fumes

• Aluminium Phosphide (AlP, Celphos)
  • $PH_3$ release (moisture/acid): $AlP + 3H_2O \rightarrow Al(OH)_3 + PH_3$
  • Cytochrome oxidase inhibitor → cellular hypoxia.
  • Garlic odor, shock, arrhythmias, ARDS.
  • Rx: Supportive, $KMnO_4$ lavage, MgSO4.

  ⭐ Aluminium phosphide poisoning has a very high mortality rate despite treatment, primarily due to profound cardiovascular shock and lack of a specific antidote.

• Paraquat (Gramoxone)
  • Redox cycling → superoxide → lung/kidney damage.
  • Oral burns, ATN, "Paraquat lung" (fibrosis). >30 mg/kg poor prognosis.
  • Dx: Urine dithionite (blue).
  • Rx: Fuller's earth, hemoperfusion. ⚠️ No O2 early.
• Zinc Phosphide ($Zn_3P_2$)
  • Rodenticide; $PH_3$ release (acid: $Zn_3P_2 + 6H^+ \rightarrow 3Zn^{2+} + 2PH_3$). Like AlP. oka

Medico-legal & Autopsy - Forensic Footprints

• Medico-legal Duties: Report under BNSS; note manner (suicide, homicide, accident, natural, undetermined).
• Autopsy Protocol:
  • External: Odors (kerosene, garlic), froth.
  • Internal: Visceral congestion.
  • Samples: Key viscera (stomach, intestine, liver, kidney), blood, urine.

  ⭐ Modern preservation for viscera includes refrigeration and specific chemical preservatives depending on target analytes; formalin interferes with many tests.

• Scene Investigation: Collect containers, residues, trace evidence.

High‑Yield Points - ⚡ Biggest Takeaways

• Organophosphates (OPs): Most common, cause cholinergic crisis (SLUDGE/DUMBELS). Antidotes: Atropine, Pralidoxime (PAM).
• Organochlorines (OCs): Cause CNS stimulation (tremors, convulsions), e.g., DDT, Endosulfan.
• Carbamates: Similar to OPs but reversible cholinesterase inhibition; PAM usually not indicated.
• Aluminium Phosphide (Celphos): Releases phosphine gas; severe cardiac toxicity, high mortality.
• Paraquat: Leads to pulmonary fibrosis ("Paraquat lung") and multi-organ failure; no specific antidote.
• Pyrethroids: Cause allergic reactions, transient neurological symptoms (paresthesia); generally less severe.