Hazard vs toxicity: Which statement is true?

• A. Hazard equals toxicity
• B. Toxicity equals hazard
• C. Exposure determines hazard
• D. Hazard = Toxicity x Exposure

Answer: (D)

The main idea is that hazard reflects the potential for harm that exists when a substance could be encountered, and that potential comes from both how toxic the substance is and how much exposure there is. Toxicity is the inherent ability of a chemical to cause harm, while exposure is how much of that chemical people or the environment come into contact with. Together, hazard is best understood as the product of toxicity and exposure: if there’s no exposure, hazard is essentially zero, even for very toxic substances; if exposure is high but the substance isn’t very toxic, the hazard isn’t as great as it would be with a highly toxic substance and high exposure; and if both toxicity and exposure are high, hazard is high. That’s why the statement Hazard = Toxicity × Exposure captures this relationship.

The other options miss the key point that exposure interacts with toxicity to create hazard, rather than hazard being equal to toxicity alone, or exposure alone determining hazard.