Osmium tetroxide is a colorless to pale yellow crystalline solid with an odor that has been described as pungent or chlorine-like (odor threshold 0.0019 ppm). There are two solid allotropes, each with its own physical properties.

CHEMICAL AND PHYSICAL PROPERTIES

DETECTION

No specific detection systems exist; samples may be analyzed for the presence of the agent using standard analytical techniques.

SYMPTOMS AND EFFECTS

Osmium tetroxide acts as a corrosive chemical, producing rapid injury.

Depending on the degree of intoxication and route of exposure, symptoms may include:

Onset may be rapid or delayed, but is usually rapid at all but very low concentrations.

MEDICAL COUNTERMEASURES

Useful Drugs	Bronchodilators	Diuretics

Initial treatment should center on preventing further exposure. Victims should be removed from the area of the cloud and decontaminated as rapidly as possible.

Eyes should be lavaged with normal saline or water for at least 15 minutes.

Necrotic tissue should be excised.

Inhalation injuries to the upper airway may be aided by cool steam inhalation and cough drops. More severe inhalational injuries will require oxygen-supplemented breathing support, including PEEP. Intubation should be initiated if there are indications of damage at the level of the larynx or below.

Diuretics (e.g., furosemide) and aerosolized bronchodilators (e.g., albuterol) may be useful for managing the effects of pulmonary edema.

There are no recognized antidotes for osmium tetroxide exposure.

PHYSICAL COUNTERMEASURES

Protective equipment (self-contained breathing equipment or gas mask, including eye protection, barrier suit) must be used. Supplied-air respirators that have a full facepiece and are operated in a pressure-demand or other positive-pressure mode should be used for high (>0.1 mg/m³) or unknown concentrations. Casualties should be decontaminated as rapidly as possible (see the section on decontamination). Remove casualties from exposure as rapidly as possible.

The agent is nonflammable; however, in combination with flammable substances, it enhances combustion and may increase the likelihood of an explosion.

Also refer to 2000 Emergency Response Guidebook (ERG2000) Guide 154.

DECONTAMINATION

Victims

Decontamination of victims is accomplished by removing the victim from the contaminated area, removal of clothing, and removal of agent present on the skin. This may be accomplished by washing with copious amounts of water, in which osmium tetroxide is soluble (5-7 g/100 mL at 25°). Note that large amounts of water must be used, as dissolved osmium tetroxide (osmic acid) is corrosive.

Eyes should be lavaged with normal saline or water for at least 15 minutes.

Property

Surface decontamination may be accomplished using warm water.

Oils with unsaturated bonds (e.g., corn oil) can be used to neutralize osmium tetroxide.

SELECTED PRECURSORS

• Osmium
• Oxygen

COMMENTS

Osmium tetroxide is used as a tissue fixative for electron microscopy. It is sold for this purpose in small quantities (gram amounts), sometimes as a solution 2% or 4%). Larger quantities may be used as catalyst sources for certain reactions. It is also used in the treatment of rheumatism as an agent for producing chemical synovectomies (an application for which nitrogen mustard has also been used).

Osmium tetroxide is not a recognized chemical warfare agent. However, if it were, its effects would probably cause it to be placed in the choking agent category.

Terrorist Use

It has been reported that a group of men arrested in England planned to add osmium tetroxide to conventional explosive devices they would detonate at sites around England. The men have been described as sympathizers or adherents of the al Qaeda terrorist group. From published reports, it appears that the amount that would have been dispersed would have been unlikely to cause fatalities, but might well have produced noticible effects.