Methyl Isocyanate (C2H3NO)

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Methyl Isocyanate (C2H3NO)
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Methyl Isocyanate - Overview

• Physical properties
• Colorless liquid with a very distinct, sharp odor
  
• Highly flammable with low flash point
• Extremely toxic to people

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Methyl Isocyanate - Overview

• A chemical intermediate in production of
  carbamate insecticides/herbicides
• 1984 accidental release in Bhopal, India killed
  3-5,000 and injured 170,000

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Methyl Isocyanate - Toxicity

• Extremely toxic to humans
• Inhalation exposure LD50 lt 200 mg/m3
• Oral exposure LD50 of 50-500 mg/kg
• 23 mg/m3 is irritating to the eyes, nose, and
  throat
• 68 mg/m3 results in a risk of severe injuries
• 225 mg/m3 may result in death

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Methyl Isocyanate - Toxicity

• OSHA / NIOSH standards for skin exposure TWA
  limit 0.02 ppm (0.05 mg/m3) IDLH 3 ppm

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Protective Equipment

• Diffuses through polyethylene and attacks most
  elastomers
• Wear protective clothing appropriate to the type
  and degree of contamination
• Positive-pressure, self-contained breathing
  apparatus (SCBA) is recommended

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Detection

• No automated detection devices found

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Decontamination

• Remove victims from the area of exposure, provide
  100 O2 if inhalation has occurred
• Remove and double-bag contaminated clothing and
  personal belongings

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Decontamination

• Eyes
• Flush with lukewarm water, 15 minutes
• Remove contact lenses
• Skin
• Flush skin and hair with water, 5 minutes
• Wash with soap and water, 15 minutes
• Rinse thoroughly

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Signs and Symptoms

• Early effects of acute inhalation gaseous
  exposure
• Eye exposure various adverse effects
• Continued exposure
• Difficulty breathing and cough develops
• Acute pulmonary edema and even acute respiratory
  distress syndrome

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Signs and Symptoms

• Skin irritant causing a burning sensation
• Absorbed through the skin

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Signs and Symptoms

• Highly toxic with oral exposure
• Reaches most organs in active form
• Systemic effects seen in animal studies
• Other systemic symptoms nausea, gastritis,
  sweating, fever, and chills

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Signs and Symptoms

• Bhopal accident
• Burning eyes most frequent symptom
• Cough associated with poor prognosis
• Other symptoms include diarrhea, shortness of
  breath
• Many deaths from secondary infections
• Severe changes in lung function, renal tubular
  necrosis, reduced liver function

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Treatment

• Basic first aid for victim
• Primarily supportive treatment
• Treat pulmonary irritation and maintain adequate
  ventilation and oxygenation

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Treatment

• Oral exposures
• Administer activated charcoal slurry (240 mL
  water / 30 gm charcoal)
• 25 to 100gm in adults and adolescents
• 25 to 50gm in children ages 1 to 12 years
• 1 gm/kg in infants less than 1 year old
• A cathartic may be beneficial

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Treatment

• Eye exposure
• Liquid
• Extremely irritating
• May cause permanent damage
• Gas
• Irritating
• Rarely causes permanent injury

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Treatment

• Eye exposure
• Corneal abrasions
• Mydriatics, systemic analgesics, and topical
  ophthalmic antibiotics
• Severe iritis
• Topical atropine or homatropine

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Treatment

• Dermal exposure
• Extremely irritating
• Treat topically
• Dermal hypersensitivity reactions
• Systemic or topical corticosteroids or
  antihistamines

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Treatment

• Inhalation
• Oxygen, ventilatory support, and an intravenous
  line
• For bronchospasm inhaled and/or parenteral
  sympathomimetics, IV theophylline, and steroids
• Hospitalize and observe all symptomatic patients
  for 72 hours for possible delayed pulmonary edema

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Treatment

• Inhalation
• Pulmonary edema
• Maintain ventilation and oxygenation
• Frequent ABGs or pulse oximetry
• Control hypoxia with O2 supplementation
• IPPB, PEEP mask or intubation

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Treatment

• Symptomatic patients
• ECG
• Chest x-ray
• Pulse oximetry
• Peak air flows
• Arterial blood gases
• Serum electrolytes
• Renal and hepatic function

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Long-Term Medical Sequelae

• Bhopal accident
• Chronic eye problems
• Pulmonary damage
• Reproductive effects
• EPA Group D
• Not classifiable as to human carcinogenicity
• Teratogenicity not defined

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Environmental Sequelae

• Rapidly hydrolyzes when released to moist soil or
  to water
• Volatilization from dry near-surface soil or
  surfaces is likely
• Bioconcentration, volatilization and absorption
  not significant processes

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Summary

• Difficult to make and safely store
• Less likely to be a terrorist weapon
• Immediate danger to life and health by inhalation
  or oral exposure
• Eye irritation to full-blown ARDS, and numerous
  serious systemic effects

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Summary

• Supportive treatment
• Treat pulmonary irritation and maintain adequate
  ventilation and oxygenation
• 1984 accidental release in Bhopal, India provides
  long-term medical consequences data