Which of the following is NOT an indicator of chemical toxicity?

The flash point refers to the lowest temperature at which a substance can vaporize to form an ignitable mixture in air. While it is an important safety characteristic that indicates how easily a chemical can catch fire and contribute to fire hazards, it does not measure or indicate the toxicity of a chemical substance.

In contrast, LD50 (lethal dose for 50% of the test population) is a direct measure of the toxicity of a chemical, as it provides information on the dose required to achieve lethal effects in half of a tested population. Flammable limits indicate the concentration range of vapors in the air that can ignite, but they are more related to flammability than toxicity specifically. Vapor pressure indicates how readily a chemical will evaporate, which can be correlated with potential exposure and toxicity since more volatile chemicals may pose greater inhalation risks.

Thus, while flash point is critical in evaluating fire and explosion risks, it is not a measure of chemical toxicity and is therefore the correct answer to the question.