Variability of biomarkers in volunteer studies: The biological component

In conclusion, volunteer studies enable the estimation of both variation in half-lives and variation in biomarker levels in the well-defined homogeneous groups. Comparison of our results with other studies indicates that variation due to biological differences within and between people is quite substantial in homogeneous exposure groups. The relative contribution of this biological component to the total variation will be smaller when variance components are estimated in less homogeneous groups, such as those in occupational and environmental settings.