Which statement about extrapolating LD50 data from animals to humans is most accurate?

• A. Directly applies to humans
• B. Requires safety factors for extrapolation
• C. Is illegal
• D. Is only for inhalation

Answer: (B)

When scientists estimate how a toxin affects humans based on animal data, they can’t rely on a direct, one-to-one translation. Animals and humans differ in size, physiology, metabolism, and how a substance is absorbed and processed. To account for these differences and for the variability among people, risk assessors apply safety factors (uncertainty factors) when extrapolating from animal LD50 data to humans. This makes the estimated human hazard more conservative and protective.

Directly applying an animal LD50 to humans would ignore these important differences, so it’s not appropriate. It isn’t illegal to use extrapolation in risk assessment, but it isn’t a simple transfer. LD50 data aren’t limited to inhalation exposure; the route of exposure matters and must be considered when assessing risk.