Problem-Based Learning Activity: Occupational Herbicide Poisoning Case Study

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Paraquat Toxicity and Treatment
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Paraquat
Paraquat is very toxic to the skin and mucous
membranes (inside of mouth, nose, eyes).
Particles are considered too large for
respiratory absorption, but once paraquat in the
system (through broken skin or mucous membranes)
it migrates to the lungs because of its oxygen
seeking properties. If ingested it is very
lethal, survival rates are generally poor.
Skin dryness, cracks erythema (redness) blistering ulcerations
Nails discoloration splitting nails loss of nails
Respiratory cough nosebleeds sore throat
Eyes conjunctivitis (irritation) ulceration, scarring, blindness
Ingestion pulmonary fibrosis multi-system organ failure, specifically respiratory failure kidney failure
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Toxicology

• Ingestion- life threatening effects on GI,
  kidney, liver and heart
• LD50 3-5mg/kg or 10-15ml in 20 solution
• Most lethal in lungs but toxicity from
  inhalation rare
• Mechanism generation of free radicals with
  oxidative damage to lung tissue
• Pulmonary fibrosis w/in 7-10 day causes death

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Source Richards, Kerry Penn State University
Extension Service
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LD50
Lethal Dose Amount of chemical it takes to kill
50 of an experimental population
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Source Richards, Kerry Penn State University
Extension Service
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Source Richards, Kerry Penn State University
Extension Service
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Adverse effects of Exposure

• GI mucous membrane swelling, edema, ulcerations
• Renal proximal renal tubule damage reversible
• Cardiac focal necrosis myocardium
• Cerebral edema and brain damage
• Smoking paraquat contaminated marijuana
  pyrolyzed to non toxic dipyridyl

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Toxicology (Skin)

• Local skin damage ? contact dermatitis
• Prolonged contact ? blisters, abrasion,
  ulcerations, finger nail changes
• Slow absorption via intact skin
• Abraded or eroded skin absorption efficient

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Treatment of Contact Dermatitis from Paraquat

• Upon contact, flush the skin with copious amounts
  of water
• Mild skin reactions are usually self limiting as
  long as there is no more contact
• More severe reaction should be treated by a
  dermatologist

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Factors Leading to Illness Event

• What the product used for its intended purpose?
• Is it registered?
• Is it registered for use on wheat alfalfa?
• Is it restricted?
• What the product used correctly?
• What factors could have lead the worker not to
  take action to mitigate the effects?