Environmental exposure to perchlorate, nitrate, and thiocyanate in relation to myopia in adolescents: a cross-sectional NHANES study

BACKGROUND: Myopia is a complex public health issue influenced by both genetic and environmental factors. The exposome concept, which considers the totality of environmental exposures, provides a crucial framework for this research. To fully understand the impact of the chemical exposome, it is necessary to evaluate both the effects of individual chemicals and their joint effects within realistic mixtures. This study aimed to characterize these distinct associations for three common environmental anions in U.S. adolescents. METHODS: We conducted a cross-sectional analysis of 2705 adolescents aged 12-18 years from the 2005-2008 National Health and Nutrition Examination Survey (NHANES). Myopia was defined as a spherical equivalent (SE) refractive error of ≤ - 0.50 diopters (D). We used weighted multivariable logistic regression to assess associations between individual urinary PNT concentrations and myopia. Weighted Quantile Sum (WQS) regression was applied to evaluate the effects of the chemical mixture. RESULTS: Our analyses revealed a complex relationship. In single-pollutant models, higher urinary perchlorate (Quartile 4 vs. Quartile 1: Odds Ratio = 0.620, 95% Confidence Interval [CI] 0.447-0.861) and nitrate (Q4 vs. Q1: OR = 0.553, 95% CI 0.398-0.769) concentrations were independently associated with lower odds of myopia. This finding was reinforced by mixture models, where a significant inverse association was also observed for the overall chemical mixture (OR = 0.592, 95% CI 0.402-0.870). WQS weights identified nitrate and perchlorate as the primary contributors of the mixture's effect. CONCLUSIONS: We observed an inverse association between urinary perchlorate/nitrate and myopia among U.S. adolescents. Findings were broadly consistent across single-pollutant and mixture analyses; however, given the cross-sectional design, non-cycloplegic refraction, and potential residual confounding and exposure misclassification, these results should be interpreted as associations and warrant confirmation in longitudinal and mechanistic studies.