Prenatal exposure in mothers and peripubertal exposure in offspring to certain phthalates, parabens, and phenols found in personal care items are associated with early puberty in adolescent girls, according to a study published in Human Reproduction.
The researchers recruited pregnant women enrolled in the Center for the Health Assessment of Mothers and Children of Salinas (CHAMACOS) from 1999 to 2000; eligibility criteria included age ≥18 years, <20 weeks’ gestation, English or Spanish speaking, and qualifying for low-income health insurance. A total of 537 children were born during the study period, and 338 (159 male and 179 female) were followed between 9 and 13 years for pubertal assessments.
Children were examined every 9 months between ages 9 and 13 years. Girls were examined for breast and pubic hair growth and asked if they had begun menstruating and, if so, the month and year of their first menses. Boys were assessed for genital and pubic hair development visually, and testicular volume was measured in comparison to orchidometer beads. Breast, genital, and pubic hair development was classified by stages of development between 1 and 5. Pubertal onset was defined as age when reaching stage B2 (thelarche) for girls or G2 (gonadarche) for boys.
Urinary samples were collected from mothers twice during pregnancy (prenatal samples) as well as from the children at the 9-year-old visit (peripubertal samples). Paraben and phenol concentrations were measured in both prenatal and peripubertal samples; phthalate metabolites were only quantified in prenatal samples. Metabolites of monoethyl phthalate (MEP), mono-n-butyl phthalate, and mono-isobutyl phthalate were analyzed. Urinary concentrations of 3 parabens (methyl-, propyl- and butyl paraben) and 4 phenols (triclosan; benzophenone-3; and 2,4- and 2,5-dichlorophenol) were also collected.
In girls, the median age of thelarche was 9.2 years; at pubarche, median age was 10.3 years, and at menarche, median age was 11.7 years. In boys, median age at gonadarche was 10.8 years and 12.2 years at pubarche. At age 9 years, 39% and 20% of girls had already reached thelarche and pubarche, respectively, and 11% and 1% of boys had reached gonadarche and pubarche, respectively.
In the urine concentration analysis, all biomarkers were found in more than 90% of samples except triclosan (73% of prenatal and 69% of peripubertal samples) and butyl paraben (<40% of samples). The researchers found an association of earlier pubertal milestones with higher concentrations of MEP, triclosan, and 2,3-dichlorophenol with prenatal urinary biomarkers; specifically, each doubling of prenatal MEP was associated with a shift in timing of pubarche by -1.3 months, and each doubling of prenatal triclosan and 2,4-dichlorophenol was associated with a shift in menarche of -0.7 months and -0.8 months, respectively.
For peripubertal exposure in girls, results showed an association of earlier thelarche (mean shift= -1.1 months), pubarche (shift= -1.5 months), and menarche (shift= -0.9 months) with each doubling of concentrations of methyl paraben and earlier pubarche with each doubling of propyl paraben (shift= -0.8 months) at age 9. Later onset of pubarche was associated with peripubertal concentrations of 2,5-dichlorophenol (shift=1.0 month). No prenatal biomarkers were associated with pubertal timing in boys; for peripubertal concentrations, results showed an association of earlier gonadarche with each doubling of propyl paraben (shift= -1.0 months).
“This study contributes to a growing literature that suggests that exposure to certain endocrine-disrupting chemicals may impact timing of puberty in children,” the authors concluded.
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