Osmium tetroxide hazards include which of the following?

• A. Causes toxic vapors, may fix corneas
• B. Non-toxic
• C. Odorless
• D. Reacts with metals

Answer: (A)

Osmium tetroxide is a highly toxic, volatile oxidizer used in histology for lipid staining, so its hazards are mainly about inhalation risk and eye damage. The correct statement points out that it releases toxic vapors and can fix corneas on exposure. Inhalation of its vapors can cause severe irritation and systemic toxicity, and contact with the eyes can lead to permanent corneal damage, sometimes described as “fixing” the cornea. It is not non-toxic, it is not odorless (it has a strong, noticeable odor), and while it can react chemically, its primary safety concerns in the lab are toxicity and ocular injury, not a general hazard of reacting with metals.