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Hydrogen Sulfide (H 2 S)

Hydrogen Sulfide (H 2 S). Hydrogen Sulfide - Overview. Colorless, irritating, flammable gas, heavier than air Rotten egg odor (concentrations > 0.5 ppm) Soluble in water, forming sulfuric acid. Hydrogen Sulfide - Overview. Commercial and industrial use Petroleum Viscose rayon Rubber

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Hydrogen Sulfide (H 2 S)

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  1. Hydrogen Sulfide (H2S)

  2. Hydrogen Sulfide - Overview • Colorless, irritating, flammable gas, heavier than air • Rotten egg odor (concentrations > 0.5 ppm) • Soluble in water, forming sulfuric acid

  3. Hydrogen Sulfide - Overview • Commercial and industrial use • Petroleum • Viscose rayon • Rubber • Food processing • Tanning • Mining industries

  4. Hydrogen Sulfide - Toxicity • Major route by inhalation • Lower doses • Eye and upper respiratory tract • Higher doses • Cellular respiration may cease • Affects all organs • Nervous system • GI absorption rarely occurs

  5. Hydrogen Sulfide - Toxicity • Children more vulnerable than adults • Most acute poisonings from accidental gas formation • OSHA standard: 20 ppm (max: 50 ppm for up to 10 minutes) • NIOSH standard: 10 ppm • Sudden death can occur at levels >700 ppm

  6. Protective Equipment • Easily detected and avoided by odor • Chemical-protective clothing advised • Breathing protection required • Positive-pressure, self-contained breathing apparatus (SCBA) • Supplied-air respirator with a full facepiece

  7. Detection • Portable and fixed gas monitors available commercially • Sensors operate in the range from 0 – 500 ppm

  8. Decontamination • Relocate exposed victims to fresh air immediately • Remove residue with soap and water • Dilute sulfuric acid with large amounts of water

  9. Signs and Symptoms • Low-level exposures common in industrial settings • Low-level exposures produce • Local eye and mucous membrane irritation • Mild systemic effects • Chemical bronchitis with repeated exposure • On exam • Evidence of conjunctivitis and wheezing • Gray-green line on the gingiva from long-term exposures

  10. Signs and Symptoms • Eye irritation develops at levels as low as 4 ppm • Pulmonary membrane irritation is evident with exposures > 20 ppm

  11. Signs and Symptoms • Higher-level exposures (50-400 ppm) • Severe cardiopulmonary and systemic effects • Continued exposure results • Pulmonary edema • Victim may present in fulminate acute respiratory distress syndrome (ARDS)

  12. Signs and Symptoms • Severe high-level exposure (>500 ppm) • Fatal systemic toxicity • Myocardial infarction, seizure, coma, and cardiopulmonary arrest • Just 2-3 breaths of HS at >700 ppm • Immediate death • Environment awareness of exposure site to determine secondary findings

  13. Laboratory • Diagnostic findings are consistent with other hemoglobinopathies • Arterial blood gases • Marked uncompensated metabolic acidosis • pO2 and calculated oxygen saturation are within reference range • Measured oxygen saturation is often low • Elevated levels of carboxyhemoglobin or methemoglobin

  14. Laboratory • Normal chest x-ray, unless pulmonary edema develops • Ischemia, infarction patterns or various arrhythmias may be evident on ECG • Chronic low-level exposures • CT or MRI scan of the head • Basal ganglia lesions • Urinary thiosulfate levels confirm exposure

  15. Treatment • Treatment based on creating methemoglobinemia • Treat initially with 100% oxygen and amyl nitrite • Sodium nitrite • Dose of 0.33 cc/kg of 3% solution, via slow IV push, to a maximum of 10 cc • Pediatric dosing is the same • Contraindication: hypersensitivity to drug

  16. Treatment • Treatment based on creating methemoglobinemia • High methemoglobin levels exacerbate ischemia in those with poor cardiopulmonary reserves • Adjust dosage for severe anemia

  17. Treatment • Control hypoxia with oxygen supplementation • To delay and/or minimize pulmonary edema • Positive airway pressure intermittent positive pressure breathing (IPPB), • Positive end-expiratory pressure (PEEP) mask • Intubation

  18. Treatment • Acute bronchospasm: aerosolized bronchodilators • For children with stridor: epinephrine aerosol • Hyperbaric oxygen (HBO) therapy is beneficial • Steroids advised if given within 15 minutes

  19. Long-Term Medical Sequelae • Delayed neuropsychiatric sequelae • Vision and memory impairment • Rigid movements, reduced motor function, slight tremor, and ataxia • Psychosis • Abnormal learning and retention • Mild cerebral atrophy • Not classified for carcinogenicity, mutagenicity or teratogenicity

  20. Environmental Sequelae • Will form sulfur dioxide and sulfuric acid in the air • Sulfur dioxide major component in acid rain • Remains in the atmosphere ~ 18 hours

  21. Summary • Potential for terrorist use • Easily produced • Highly toxic • Capable of producing panic and disruption • Exposure by inhalation • Toxic effects include hemoglobinopathy, disrupting cellular respiration

  22. Summary • Low-level exposures • Eye and mucous membrane irritation • Higher exposures • Cardiopulmonary and CNS effects • Pulmonary edema, myocardial infarct and death • Methemoglobinemia treatment • Antidote: Sodium nitrite

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