6.5 Routes of Exposure, Symptoms & First Aid

6.5 Routes of Exposure, Symptoms & First Aid

Preventing pesticide poisoning requires a thorough understanding of how chemicals enter the human body, how different chemical classes disrupt human physiology, and what immediate emergency actions must be taken when an accidental exposure occurs.

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The Four Primary Exposure Routes

1. Dermal Exposure (Skin Contact): Accounts for over 90% of all occupational pesticide exposures among agricultural and commercial applicators. Dermal contact occurs during splashing while mixing, touching contaminated hose lines or foliage, or wearing chemical-soaked clothing.
   • Regional Absorption Rates: Dermal absorption efficiency is not uniform across the human body. Relative to the forearm (assigned a baseline absorption index of 1.0):

1. Inhalation Exposure (Breathing): Inhaling fine spray mists, dusts, powders, thermal fogs, or fumigant gases. The lungs possess a massive surface area lined with delicate capillary membranes, allowing pesticide vapors to pass directly into the bloodstream without hepatic (liver) filtration.
2. Oral Exposure (Ingestion): Swallowing pesticide chemicals. Most oral exposures result from severe carelessness: eating, drinking, or smoking with unwashed hands; storing pesticides in unlabeled beverage bottles; or clearing clogged spray nozzles by blowing through them with the mouth.
3. Ocular Exposure (Eye Contact): Direct contact with liquid splashes or airborne dusts. The eyes are highly vascularized tissues; liquid pesticides can cause severe corneal scarring or blindness while being absorbed rapidly into systemic circulation.

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Poisoning Symptoms by Chemical Class

Organophosphates & Carbamates

• Mechanism: Inhibit the essential enzyme acetylcholinesterase (AChE). AChE normally breaks down acetylcholine, a neurotransmitter that signals nerve impulses to muscles and glands. When AChE is inhibited, acetylcholine accumulates at nerve synapses, causing continuous, uncontrolled hyperstimulation of the nervous system.
• Symptoms: Early signs include headache, dizziness, nausea, excessive sweating, and salivation. Advanced poisoning triggers the SLUDGE acronym:
  • Salivation (uncontrolled drooling)
  • Lacrimation (excessive tearing)
  • Urination (involuntary bladder release)
  • Defecation (diarrhea)
  • Gastrointestinal cramping
  • Emesis (vomiting)
  • Accompanying diagnostic signs include pinpoint pupils (miosis), muscle twitching, chest tightness, respiratory failure, convulsions, and death.
• Medical Antidote: Atropine sulfate blocks acetylcholine receptors, while 2-PAM (pralidoxime chloride) reactivates the AChE enzyme (effective for organophosphates if administered promptly).

Pyrethroids & Synthetic Pyrethroids

• Mechanism: Disrupt sodium channel gating in nerve membranes.
• Symptoms: Skin tingling, burning, or numbness (paresthesia), facial itching, coughing, dizziness, and mild nausea. Symptoms are generally transient but exacerbated by sweating.

Herbicides & Fungicides

• 2,4-D / Phenoxy Herbicides: Gastrointestinal irritation, muscle weakness, slurred speech.
• Paraquat / Diquat (Bipyridyliums): Paraquat is extremely toxic. Swallowing even a single mouthful causes severe mouth ulceration followed by delayed, irreversible pulmonary fibrosis (scarring of lung tissue leading to fatal suffocation).
• Fungicides: Most cause localized contact dermatitis, eye irritation, or throat burning, though some organometallic fungicides present systemic kidney and liver risks.

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Emergency First Aid Procedures

FIRST RULE OF FIRST AID: Protect yourself first. Never enter a contaminated space or touch an exposed victim without wearing appropriate chemical-resistant PPE.

+-------------------------------------------------------------------------+
|                    EMERGENCY FIRST AID FLOWCHART                        |
+-------------------------------------------------------------------------+
|  1. EYE CONTACT: Flush eyes with clean water for 15+ minutes.           |
|  2. SKIN CONTACT: Strip clothing; drench & wash with soap and water.    |
|  3. INHALATION: Move to fresh air; loosen clothing; CPR with barrier.   |
|  4. INGESTION: Call Poison Control (1-800-222-1222); check label rules. |
+-------------------------------------------------------------------------+

Detailed First-Aid Actions

1. Eye Exposure: Hold eyelids open immediately and flush eyes with a continuous, gentle stream of clean, lukewarm water or saline for at least 15 minutes. Do not use eye drops or chemicals in the wash water. Cover eye loosely with a clean cloth and seek immediate medical attention.
2. Dermal Exposure: Remove all contaminated clothing, shoes, and socks immediately. Drench skin with clean water. Wash skin, hair, and fingernails thoroughly with mild soap and water. Gently dry skin and wrap in clean blankets. Never use harsh scrub brushes that break the skin barrier.
3. Inhalation Exposure: Immediately carry or escort victim into fresh, uncontaminated air. Loosen tight collar and belt. If breathing has stopped, administer artificial respiration (CPR). Do not perform mouth-to-mouth CPR if pesticide residue is visible on the victim's face; use a pocket mask fitted with a one-way valve.
4. Oral Ingestion Protocol & Vomiting Rules:
   • Immediately call Poison Control (1-800-222-1222) or an emergency medical responder.
   • NEVER INDUCE VOMITING IF:
     • The victim is unconscious, in shock, or having convulsions.
     • The product label specifically prohibits inducing vomiting.
     • The pesticide is an Emulsifiable Concentrate (EC) or contains petroleum distillates/solvents. Vomiting causes liquid solvent vapors to enter the lungs (aspiration), resulting in fatal chemical pneumonitis.
     • The pesticide is a strong corrosive acid or alkali. Vomiting severely burns the esophagus and throat a second time.