How is carcinogenicity evaluation and cancer risk quantified?

• A. Using human epidemiological data alone.
• B. Using only in vitro data.
• C. Using animal and mechanistic data; cancer risk is quantified with cancer slope factors or BMD/BMDL.
• D. Using only pharmacokinetic data.

Answer: (C)

Carcinogenicity assessment and cancer risk quantification rely on data from animal studies showing dose–response to identify whether a substance increases cancer risk, with mechanistic information helping to judge how relevant that mode of action is to humans. From these data, a point of departure is established and then translated into human risk using quantitative models such as cancer slope factors or benchmark dose approaches (with the BMDL as the lower confidence limit). These tools provide a numeric estimate of incremental cancer risk per unit of lifetime exposure, allowing comparison across substances and exposure scenarios. Human epidemiology can inform the assessment, but on its own it is rarely sufficient to quantify risk for a wide range of chemicals, and in vitro or pharmacokinetic data alone do not yield a full quantitative cancer risk estimate.