BOT/MICRO/ZOOL 5364

TOXICITY OF CHEMICALS USED IN ELECTRON MICROSCOPY

I. Fixatives:

Osmium tetroxide - Vapors are irritating to eyes and mucous membranes.  Strong vapors may result in sore throat and can attack the cornea causing partial blindness.  Use proper ventilation.  Only use in fume hood!

Glutaraldehyde, Acrolein, etc. - Noxious odors, irritating to respiratory tract and mucous membranes.  Use proper ventilation. Acrolein only in fume hood!

II. Buffers:

Cacodylate (salts of di-methyl arsinic acid, (CH₃)₂AsOOH) - All arsenic compounds are highly toxic; chronic poisoning can result from continuous exposure to relatively small amounts (300 µg*per day, not as bad as lead salts in this regard).

s-Collidine (tri-methyl pyridine) - Noxious vapors, toxic in moderate concentration.  Volatile in solution.  Use proper ventilation.  Use fume hood.

Veronal (Barbital) - Not toxic in moderate quantities, but a habit-forming barbituate.  Requires Class IV narcotics permit.

III. Dehydrating Agents:

Ethanol - No problem except for solutes that may be added.  Must be highly diluted to dispose with water.  Contaminated ethanol must be disposed of properly (e.g., if it contains lead or uranium salts).

Acetone - Vapors relatively irritating but not very toxic.  Extremely small amounts in atmosphere cause headaches in many people.  Merck Index gives maximum allowable concentration as 500 ppm.  Highly flammable.  Use proper ventilation and keep away from flames.

IV. Embedding Agents:

Plastics - Generally low toxicity, but may cause allergic reaction on repeated contact.  Some resins may contain reactive components which produce allergies on short-term exposure. 

Catalysts:  DMP-30, BDMA - Reactive compounds which may be absorbed through skin.  Not highly toxic, but should be used with caution.

V. Stains:

Lead stains (Reynolds', Millonig's, etc.) - All lead salts are highly poisonous.  Continuous exposure to small amounts (as little as 60 µg*per day) can cause chronic poisoning.

A serious danger is the inhalation of particles, i.e., dust during the preparation of solutions, or insoluble Pb carbonate crystals produced by the evaporation of staining solutions.

Uranyl acetate: Mildly radioactive and highly toxic - to be treated with considerable caution, especially in dry form (the reagent itself or evaporated staining solution).  Merck Index gives maximum allowable concentration as 20 µg/cubic meter.

Some suggested general precautions:

(1)       Use proper ventilation when handling volatile chemicals.

(2)       Weigh heavy-metal salts in a hood; do not allow solutions of heavy metals (Pb and Uranium stains) to dry to dust, where they may become an airborne contaminant!

(3)       Food is not permitted in labs and should never be kept in laboratory refrigerators.

For references, see:

The Merck Index of Chemicals and Drugs, many editions are out there.

Material Safety Data Sheets (MSDS)  - available from manufacturer and from web resources for each chemical

Chemical Hygiene Plan (CHP) – available in NML 206 and on OU web site.

Office of Environmental Safety, University of Oklahoma

Occupational Safety and Health Act (OSHA), US government site