Biomonitoring as a method for assessing exposure to perchlorate.

Biomonitoring provides direct and quantitative information regarding human exposure to environmental toxicants, such as perchlorate (ClO(4)(-)). Because of concerns surrounding widespread exposure to ClO(4)(-), we are using biomonitoring methods to assess exposure to ClO(4)(-) and other physiologically relevant anions that can impact iodide uptake by the thyroid. These methods quantify ClO(4)(-), thiocyanate, nitrate, and iodide in human urine, milk, serum, blood spots, amniotic fluid, and infant formula using ion chromatography coupled with electrospray ionization tandem mass spectrometry. In this paper we summarize recent ClO(4)(-) biomonitoring research and provide three additional examples of the utility of biomonitoring for characterizing ClO(4)(-) exposure. Specifically, we examine variability in ClO(4)(-) excretion, compare the relative importance of different exposure sources in adults, and estimate ClO(4)(-) exposure in formula-fed infants. These applications provide examples of how biomonitoring can improve individual exposure assessment. Individual biomarker data can subsequently be compared with individual thyroid function data to better evaluate potential linkage between ClO(4)(-) exposure and health.