Biomarkers can be categorized into biomarkers of exposure and biomarkers of effect. Which statement correctly defines them?

• A. Biomarkers of exposure measure internal dose; biomarkers of effect indicate early biological changes.
• B. Biomarkers of exposure measure external dose; biomarkers of effect indicate environmental concentration.
• C. Biomarkers of exposure detect genetic mutations; biomarkers of effect measure dose.
• D. Biomarkers of exposure assess risk communication; biomarkers of effect measure exposure levels.

Answer: (A)

In toxicology, biomarkers are used to separate two kinds of information: what has entered the body and how the body responds. Biomarkers of exposure reflect the internal dose—the amount of chemical that has actually been absorbed—and are typically measured in biological samples like blood or urine as the chemical itself or its metabolites. This tells you how much exposure occurred and progressed inside the body.

Biomarkers of effect, on the other hand, signal early biological responses to that exposure. They track changes at the molecular or cellular level—such as enzyme activity changes, DNA damage, oxidative stress, or altered gene expression—that indicate the body is responding to the chemical, potentially before any disease develops.

So, the best statement is that exposure biomarkers measure internal dose, while effect biomarkers indicate early biological changes. External environmental concentrations or genetic mutations, risk communication, or dose-focused descriptions do not capture this same internal-dose versus early-response distinction.