Exposure Assessment of the Developing Fetus and Newborn Infants: Methods to Measure Perchlorate and Related Anions in Maternal and Fetal Matrices

Abstract

S-30B9-3 Background/Aims: Perchlorate is a commonly occurring environmental toxicant that may impair iodide transport, and thus compromise development of the fetus and neonate. Therefore, we developed analytical methods for quantifying perchlorate and toxicologically related anions (iodide, nitrate, thiocyanate) in physiological fluids relevant to fetal and neonatal exposure. Methods: We used ion chromatography coupled with electrospray ionization tandem mass spectrometry to accurately and precisely quantify background levels of perchlorate and related anions in urine and serum from pregnant women; amniotic fluid from the fetus; and cord blood, dried blood spots, and diaper press urine from newborns. Additionally, we validated methods for quantifying perchlorate and related anions in breast milk and infant formula so that perchlorate intake could also be calculated. We found that sample collection materials (eg, diapers and blood spot paper) are potential sources of perchlorate contamination. Results: Perchlorate was commonly found in maternal, fetal, and newborn matrices. Maternal urinary perchlorate levels were positively correlated with perchlorate levels in amniotic fluid (r = 0.57). Maternal serum perchlorate was generally higher than cord serum perchlorate (median ratio 2.4:1 for paired samples); conversely, iodide levels were typically higher in fetal fluids compared to maternal fluids. Perchlorate exposure doses were subsequently estimated for 91 infants based on multiple urine samples collected over the first year of life. The median estimated exposure dose was 0.160 μg/kg/d, with 9% of the estimated doses exceeding the US EPA reference dose of 0.7 μg/kg/d, and breast-fed infants having greater perchlorate exposure than formula-fed infants. Conclusion: Maternal urine perchlorate is an effective surrogate measure of fetal perchlorate exposure. Perchlorate does not appear to disproportionately accumulate in the fetal compartment; however, infants likely have higher perchlorate exposure doses than adults (medians of 0.160 and 0.064 μg/kg/d, respectively).