Communities living near areas with degraded environmental conditions expect clear answers regarding their health from public health authorities. In recent years, there has been a growing demand for the use of biomarkers that reflect internal exposure to pollutants and are perceived as less prone to uncertainty. These biological assays fall under two public health approaches: “screening” and “measurement of exposure or accumulation.” Screening allows individuals to benefit from the results of the biological assay; appropriate procedures and communication strategies will be implemented to reach as many people as possible. The biological exposure study primarily aims to improve knowledge; the issue of selecting a representative sample of the population to achieve this objective is systematically necessary. Screening results are primarily reported as a percentage of the population, or population category, that tested positive; exposure study results are reported through the distribution of biomarker results within the population. Screening and biological exposure studies therefore differ in their purposes, objectives, organizational methods, expected results, and interpretation. This distinction is significant. (R.A.)