Maternal Urinary Triclosan Concentration in Relation to Maternal and Neonatal Thyroid Hormone Levels: A Prospective Study

BACKGROUND Triclosan (TCS) is a synthetic antibacterial chemical widely used in personal care products. TCS exposure has been associated with decreased thyroid hormone levels in animals, but human studies are scarce and controversial. OBJECTIVE We evaluated the association between maternal TCS exposure and thyroid hormone levels of mothers and newborns. METHODS TCS was measured by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) in urine samples collected during gestational weeks 38.8±1.1 from 398 pregnant women in a prospective birth cohort enrolled in 2012-2013 in Shanghai, China. Maternal serum levels of free thyroxine (FT4), thyroid-stimulating hormone (TSH), and thyroid peroxidase antibody (TPOAb) were obtained from medical records. Cord blood levels of free triiodothyronine (FT3), FT4, TSH, and TPOAb were measured. Multiple linear and logistic regression models were used to examine the relationship between maternal urinary TCS and thyroid hormone levels. RESULTS TCS was detectable (≥0.1 ng/mL) in 98.24% of maternal urine samples with tertile of urinary TCS levels: low (>0.1-2.75 μg/g.Cr), medium (2.75–9.78 μg/g.Cr), and high (9.78–427.38 μg/g.Cr). With adjustment for potential confounders, cord blood log(FT3)pmol/L concentration was 0.11 lower in newborns of mothers with medium and high urinary TCS levels compared with those with low levels. At third trimester, the high TCS concentration was associated with 0.03 [95% confidence interval (CI) −0.08, −0.02] lower maternal serum log(FT4)pmol/L, whereas the medium TCS concentration was associated with 0.15 (95% CI: −0.28, −0.03) lower serum log(TSH)mIU/L with adjustment for covariates. CONCLUSIONS Our results suggest significant inverse associations between maternal urinary TCS and cord blood FT3 as well as maternal blood FT4 concentrations at third trimester. https://doi.org/10.1289/EHP500.