Purpose of review: We offer here a review of intraindividual variability in urinary biomarkers for assessing exposure to nonpersistent chemicals. We provide thoughts on how to better evaluate exposure to nonpersistent chemicals.
Recent findings: We summarized reported values of intraclass correlation coefficients and found that most values fall into categories that indicate only poor to good reproducibility. Even within the "good" classification, a large percentage of study participants is likely to be misclassified as to their exposure. There is sufficient information to support the statement that studies using only one spot measurement of a nonpersistent chemical will be unreliable. It is unequivocal that multiple samples have to be collected over a period of toxicological relevance and with consideration of exposure patterns. Sponsors of research and researchers themselves should be vocal about ensuring that sufficient resources are made available to properly characterize exposures when studying nonpersistent chemicals. Otherwise, we will continue to see an ever-growing body of literature yielding inconsistent and/or uninterpretable results.
Keywords: Biomonitoring; Epidemiology; Exposure; Intraclass correlation coefficient (ICC); Nonpersistent; Short-lived chemical.