Perinatal Exposure to Perchlorate, Thiocyanate, and Nitrate in New Jersey Mothers and Newborns

Abstract

Perchlorate is a commonly occurring environmental toxicant that may be transported across the placental barrier by the sodium-iodide symporter (NIS), possibly resulting in both increased perchlorate exposure and decreased iodide uptake by the fetus. Therefore, we measured levels of three physiologically relevant NIS-inhibitors (perchlorate, nitrate and thiocyanate) and iodide in maternal and fetal fluids collected during cesarean-section surgeries on 150 U.S. women. Geometric means of perchlorate, thiocyanate and nitrate levels in maternal urine (2.90, 947 and 47900 µg/L, respectively) were similar to previously published results, while urinary iodide levels (1420 µg/L) were significantly higher (p<0.0001), likely because of prevalent prenatal vitamin use in the study population (74%). Thiocyanate levels were higher in the maternal serum, cord serum, and amniotic fluid of smokers compared to women with environmental tobacco smoke exposure and non-smokers (p-values of 0.0006, p=0.0011, and 0.0026, respectively). Perchlorate was detected in most samples: urine (100%), maternal serum (94%), cord serum (67%), and amniotic fluid (97%). Maternal urinary perchlorate levels were positively correlated with perchlorate levels in amniotic fluid (r=0.57), indicating that maternal urine perchlorate is an effective biomarker of fetal perchlorate exposure. Maternal serum perchlorate was generally higher than cord serum perchlorate (median ratio 2.4:1 for paired samples), and maternal urine perchlorate was always higher than fetal amniotic fluid perchlorate levels (mean ratio 22:1); conversely, iodide levels were typically higher in fetal fluids compared to maternal fluids. We found no evidence of either disproportionate perchlorate accumulation or lack of iodide in the fetal compartment. In this panel of healthy infants, we found no association between cord blood levels of these anions and newborn weight, length and head circumference.

Association of prenatal perchlorate, thiocyanate, and nitrate exposure with neonatal size and gestational age

“…Among the few studies that have looked at differences in fetal growth in relation to maternal NIS inhibitor exposure, maternal exposure classification has been primarily based on the concentrations of NIS inhibitors in drinking water, with no direct assessment of biological toxicant concentrations [16,18,22]. Bukwoski et al observed up to a 156% (95% CI: 44–445%) greater odds of intrauterine growth restriction (<2500 g at birth) among infants born to mothers whose residence at the time of delivery was in a community with higher concentrations of nitrate in the drinking water, compared to areas with the lowest nitrate levels [18].…”

“…Previously, we reported strong positive correlations between maternal urinary concentrations of NIS inhibitors and concentrations in cord blood and amniotic fluid [22]. suggesting that maternal urinary measures of these NIS inhibitors may be effective surrogates for fetal exposures.…”

Dose-Response Relationship Between Orally Administered Ammonium Perchlorate and Urine Perchlorate Concentrations in Rats: Possible Biomarker to Quantify Environmental Ammonium Perchlorate Exposure on Thyroid Homeostasis

“…Useful human exposure data have been obtained by directly measuring levels of perchlorate in human urine, milk, amniotic fluid, saliva, and blood. [9][10][11][12][13][14] Quantification of perchlorate in biological tissues and fluids is an excellent method for evaluating both the prevalence and magnitude of exposure. 15 Furthermore, measurement of perchlorate in biological matrices provides data on the total dose of perchlorate integrated from all sources.…”

Placental transfer of and infantile exposure to perchlorate

“…1), but were much lower than those in maternal (mean: 13.2 ± 1.70 ng mL À1 ) and cord serum (19.9 ± 5.00 ng mL À1 ) samples obtained in a city of Chile (Lumen et al, 2013). However, it should (Asami et al, 2013;Blount et al, 2009;Borjan et al, 2011;Dasgupta et al, 2008;Her et al, 2010;Kirk et al, 2007;Kirk et al, 2005;Kirk et al, 2012;Lee et al, 2012;Leung et al, 2012;Leung et al, 2009;Lumen et al, 2013;Pearce et al, 2007;Wang et al, 2011;Valentin-Blasini et al, 2011). In this study, breast milk and infants' urine were recruited in Nanchang; cord blood samples were obtained in Tianjin; infant formula samples from ten manufacturers representing >80% of the Chinese market were purchased from retail stores.…”