Prenatal and peripubertal exposure to certain endocrine-disrupting chemicals in personal care products may disrupt pubertal timing in girls, according to study results published in Human Reproduction.
The study followed 338 children and their mothers (333 of whom were Latina) who were enrolled in the Center for the Health Assessment of Mothers and Children of Salinas, a longitudinal birth cohort studying the effects of in utero and early life environmental exposures on childhood health and development. At 2 interviews during pregnancy, maternal urine samples were assessed for metabolites known to be used in personal care products: monoethyl phthalate, mono-n-butyl phthalate, and mono-isobutyl phthalate, as well as methyl-, propyl-, and butylparaben and 4 phenols (triclosan, benzophenone-3 and 2,4- and 2,5-dichlorophenol).
At age 9 years, urine samples from the children were screened for the same chemicals. The researchers relied on clinical Tanner staging to measure puberty timing and the children were examined every 9 months between ages 9 to 13 years.
Median age at thelarche, pubarche, and menarche in girls was 9.2 years, 10.3 years, and 11.7 years, respectively. In boys, the median age at gonadarche and pubarche was 10.8 years and 12.2 years, respectively. At age 9, 39% and 20% of girls had reached thelarche and pubarche, respectively, and 11% and 1% of boys had reached gonadarche and pubarche, respectively. All biomarkers were detected in >90% of laboratory samples except triclosan, which was detected in 73% of prenatal and 69% of peripubertal samples, and butyl paraben, which was found in <40% of the samples and subsequently excluded from the analyses.
In girls, researchers noted associations between early pubertal onset and prenatal exposures. Specifically, each doubling of prenatal monoethyl phthalate concentration was associated with earlier onset of pubarche by -1.3 months (95% CI, -2.5 to -0.1; P <.05) and each doubling of concentration of prenatal triclosan and 2,4-dichlorophenol was associated with earlier menarche of -0.7 months (95% CI, -1.2 to -0.2; P <.01) and -0.8 months (95% CI, -1.6 to 0.0; P <.05), respectively. The researchers also reported associations between peripubertal methyl paraben exposure and earlier thelarche, pubarche, and menarche. In boys, researchers noted no association between prenatal urinary biomarker concentrations and puberty onset and only one association with peripubertal concentrations — earlier gonadarche with greater exposure to propyl paraben.
The researchers cautioned that the chemicals studied metabolize quickly, so that urinary measurements may not reflect usual exposure. They also noted that the findings may not be widely generalizable due to the homogeneity of the study population and that the associations reported could result from reverse causality (eg, children entering puberty early may be more likely to use personal care products).
The investigators concluded that “this study contributes to a growing literature that suggests that exposure to certain endocrine disrupting chemicals may impact timing of puberty in children.”
Harley KG, Berger KP, Kogut K, et al. Association of phthalates, parabens and phenols found in personal care products with pubertal timing in girls and boys [published online December 4, 2018]. Hum Reprod. doi:10.1093/humrep/dey337