Serum PFAS concentrations and circulating vitamin D in U.S. children: evidence of a paradox.

Abstract

This study examined the relationship between serum PFAS concentrations and vitamin D levels in prepubertal children. Data were drawn from the 2013-2014 cycle of a nationally representative survey, including serum samples from children aged 3-11 years (N = 523). Five newly corrected PFAS components, commonly detected among study participants, were analyzed: PFNA, PFHxS, n-PFOA, n-PFOS, and Sm-PFOS. Combined PFAS toxicity was assessed using total PFOA equivalents. Positive correlations were observed between age- and sex-adjusted vitamin D z-scores and five PFAS, with unweighted correlation coefficients ranging from 0.02 (PFNA and n-PFOA) to 0.10 (Sm-PFOS and Mix PFOA EQ). After adjusting for covariates, a one standard deviation increase in Sm-PFOS (1.36 ng/mL) was associated with a 0.46 ng/mL increase in serum vitamin D. Children with n-PFOA levels >2.59 ng/mL (3rd quarter) had a significantly lower prevalence of vitamin D insufficiency (prevalence ratio = 0.55; 95% CI: 0.31, 0.98). Higher serum PFAS concentrations were associated with higher vitamin D levels in prepubertal children. While this may appear beneficial, it contrasts with growing evidence that PFAS disrupts growth and development. This paradoxical pattern may reflect PFAS-related vitamin D resistance, though functional implications cannot be determined from cross-sectional data. Higher serum PFAS concentrations were associated with elevated vitamin D levels in prepubertal children. Elevated serum vitamin D in PFAS-exposed children may reflect a compensatory response to impaired vitamin D receptor function rather than improved nutritional status. Our findings caution clinicians that normal or elevated serum vitamin D levels may mask deeper endocrine and developmental disruptions in children, especially in the context of PFAS exposure.