Which hazard is associated with osmium tetroxide?

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

Answer: (A)

Osmium tetroxide presents a volatile, highly toxic hazard due to the vapors it releases. Inhalation can irritate or damage the respiratory tract, and exposure can fix ocular tissue, including corneas, leading to serious eye injury or blindness. This combination of toxic vapors and potential corneal fixation is the primary danger in the lab, which is why this option is the best choice. It is not simply non-toxic, it is not odorless (the smell is a warning sign for exposure), and while it acts as a strong oxidizer, the critical hazard tested here is the toxic vapors and corneal fixation rather than any generalized reactivity with metals.