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How to Handle Osmium Tetroxide  
Summary: Follow these guidelines to protect yourself from injury when work involves osmium tetroxide.

Osmium tetroxide (OsO4) is generally used either as a primary or secondary fixative on membranes for use under electron microscopy in a laboratory environment.

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What to do How to do it
Obtain approval before beginning work. Request prior approval from your principal investigator (PI) before beginning any new project involving osmium tetroxide.
Evaluate the hazards before beginning work.
  • Consult safety resources available on the web:
  • Know about these physical characteristics:
    • Osmium tetroxide is:
      • Noncombustible
      • Colorless to pale yellow-green when solid
      • Moderately soluble in water
      • A strong oxidizer
    • Osmium tetroxide will sublime (pass directly from solid to vapor and back to solid) readily at room temperature and significantly when refrigerated.
  • Consider these hazards specific to osmium tetroxide:
    • Highly toxic (LD50 oral [rat] 14 mg/kg)
    • Ingesting very small amounts can cause death.
    • Severe irritant to the eyes and respiratory tract
    • Acute or chronic exposure can be severe with the following possible results:
      • Severe damage to the eyes, even blindness
      • Dermatitis
      • Inhalation can lead to lung or kidney damage
      • Chemical burns to the respiratory tract
  • If possible, use a less dangerous product that can perform the same task.
Follow these training guidelines. A PI or a knowledgeable designee must provide appropriate safety training.
  • Inform employees about handling osmium tetroxide, its specific hazards, and health effects.
  • Explain possible routes of exposure, as appropriate:
    • Skin absorption
    • Ingestion
    • Inhalation
  • Provide personal protective equipment and engineering controls, and train employees in their proper use.
  • Post emergency procedures in the lab and make sure everyone who works with osmium tetroxide is familiar with them.
  • Consult the chemical safety officer, (858) 822-1579, on training procedures for any new or revised projects involving large quantities of osmium tetroxide.
  • Keep training records on file, including:
    • Information covered
    • Date
    • Names
    • Employee signatures
Be prepared for accidental spills. Osmium tetroxide spills are very serious and require immediate cleanup.
  • Keep a chemical spill kit easily accessible.
  • Read How to Handle Chemical Spills in Laboratories.
  • Print and keep the Material Safety Data Sheet for osmium tetroxide with your emergency supplies.
  • Know the location of safety equipment, including eyewash, shower station, first aid kit, and Emergency Guide.
  • Clean up only small quantities of osmium tetroxide, and only if you have been properly trained.
    • Note: Corn oil deactivates osmium tetroxide.
    • Use chemical absorbent pads for solutions, as described in the chemical spill kit instructions.
    • Cover solid osmium tetroxide spills with sand, sweep up, and place in a tightly sealed container.
  • Dispose of all spill containment material as hazardous waste.
Follow these purchasing and storage guidelines.
  • Buy the least amount of osmium tetroxide the work requires. Do not buy in large quantities to save money.
  • Label all containers with this information:
    • Name of the material
    • Concentration
    • Warnings
    • Date
    • Preparer's initials
  • Label the work area with a sign saying "Osmium Tetroxide Use Area."
  • Follow these storage guidelines:
    • Store in a tightly sealed container.
    • Place the container in a secondary container large enough to capture the entire contents should the primary container leak or rupture.
    • Store away from acids, bases, metals, strong reducing agents, and strong oxidizing agents.
    • Store separately from hydrochloric acid. Osmium tetroxide reacts with hydrocholoric acid to form chlorine gas.
    • Refrigerated osmium tetroxide: Put the osmium tetroxide in a glass-vacuum-type blood collection tube to prevent vapors from escaping into the refrigerator.
Control the hazards.
  • Engineering controls: Work with osmium tetroxide in a chemical fume hood to reduce risk of inhalation. Never work with it on the open bench top.
  • Wear this personal protective equipment (PPE):
    • Lab coat with sleeves fully extended to the wrists
    • Safety glasses or splash goggles
    • Two layers of nitrile surgical gloves
    • Full-length pants
    • Closed-toe shoes
    Follow these PPE guidelines:
    • Always double-check your PPE before each use of osmium tetroxide.
    • Never re-use disposal gloves.
    • Leave all personal protective equipment in the lab when your work is complete.
  • Restrict access to the work area.
  • Keep container sizes and quantities in the work area as small as possible.
  • Perform a dry run to work out any potential pitfalls.
  • If you suspect equipment has been contaminated with osmium tetroxide, contact an EH&S; Research Assistance Program specialist.
Act quickly if an exposure occurs. Give first aid treatment, then seek medical attention immediately for any and all osmium tetroxide exposures. Treat any exposure seriously, no matter how slight it may seem at the moment.
  • Ingestion: Seek medical attention immediately.
  • Skin exposure: Flush exposed skin with water for at least 15 minutes while removing any contaminated clothing.
  • Eye exposure: Flush eyes with water for at least 15 minutes. Affected individuals may need help holding their eyes open under water.
  • For all exposures:
    • Seek medical attention immediately at an emergency room.
    • Call Campus Police at (858) 534-4357 (534-HELP) and request an ambulance if transportation is necessary.
    • Call the Poison Control System, (800) 876-4766, if additional information is needed.
Dispose of waste properly.

If you are a UCSD employee and have questions, contact the chemical safety officer, (858) 822-1579.

Notice: Disposal of hazardous waste using sinks, intentional evaporation, or as regular trash is against the law. Campus laboratories must abide by strict state and federal waste disposal requirements. You may be held liable for violations of applicable laws.

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