Mixed exposure to phthalates and organic UV filters affects Children's pubertal development in a gender-specific manner

Background: Previous studies showed phthalates and UV filters are endocrine-disruptive and associated with puberty. However, few studies have examined effects of mixed exposure.

Methods: Six phthalate metabolites and 12 organic UV filters were detected among 223 school-age children. Puberty development was evaluated at baseline and after 18 months of follow-up. Ordered logistic regression models, least absolute shrinkage and selection operator (LASSO) regression and quantile-based g-computation (qgcomp) were used to evaluate relationships between phthalate metabolites or UV filters exposure and pubertal development.

Results: Six phthalate metabolites and 5 UV filters were detectable in urine samples. In boys, BP-3 and 4'-MAP were negatively associated with genital (ORBP-3 = 0.52, (0.27, 0.93), OR4'-MAP = 0.45, (0.25, 0.74)) and pubic hair development (ORBP-3:0.24, (0.05, 0.76), OR4'-MAP:0.24, (0.05, 0.77)). In girls, MEP levels were associated with advanced breast development (OR: 1.29, (1.04, 1.64)). LASSO regression identified BP-3, 4'-MAP, and OD-PABA for inverse associations with pubertal development in boys. MEP was related to an increase in girls' breast development (OR: 1.64, (1.08, 2.63)). Overall mixture was related to a 70% reduction in boys' genital development stage, with a larger effect size than a single chemical in qgcomp. Mixed exposure was associated with girls' earlier puberty onset (OR: 2.61, (1.06, 6.42)).

Conclusions: Our results suggested higher levels of phthalate metabolites and UV filters were associated with delayed pubertal development in boys but with earlier puberty in girls. Higher effect size of joint exposure than single chemicals suggested phthalates and UV filters might have synergistic effects on puberty and distort adolescent endocrine function together.