# Long-term exposure to PM2.5 and NO2 and risk of myopia in Chinese school-aged children: a cross-sectional study

## TL;DR

This study found that long-term exposure to PM2.5 is linked to increased myopia risk in Chinese children, with higher risks at lower pollution levels.

## Contribution

The study reveals a non-linear dose-response relationship between PM2.5 exposure and myopia, showing increased risk at lower concentrations.

## Key findings

- Each IQR increase in PM2.5 exposure was associated with higher odds of myopia (OR = 1.63).
- Non-linear modeling showed a steep risk increase at lower PM2.5 concentrations followed by a plateau.
- Higher NO2 exposure quartiles were consistently linked to increased myopia risk compared to the lowest quartile.

## Abstract

To explore the link between long-term exposure to fine particulate matter (PM2.5) and nitrogen dioxide (NO2) and myopia prevalence in Chinese school-aged children.

Conducted from September 2023 to June 2024, this cross-sectional study included 23,983 school-aged children from six cities across China. Myopia was defined using non-cycloplegic refraction (SE < -0.50 D) combined with visual acuity testing. Three-year average concentrations of pollutants were sourced from the China High Air Pollutants (CHAP) dataset. We employed adjusted mixed-effects models to evaluate the relationship between exposure to air pollutants and the risk of myopia.

In adjusted linear models, each interquartile range (IQR) increase in long-term PM2.5 exposure was associated with significantly higher odds of myopia (odds ratio [OR] = 1.63; 95% confidence interval [CI]: 1.14–2.33). However, non-linear modeling identified a pronounced departure from linearity (P for non-linearity < 0.001), characterized by a steep risk increase at lower concentrations followed by a plateau at higher levels. Consistent with this pattern, categorical analyses showed that children in PM2.5 exposure quartiles Q2-Q4 had substantially elevated odds of myopia compared with Q1 (OR range: 3.30–3.59).For NO2, the per-IQR association was not statistically significant (OR = 0.96; 95% CI: 0.84–1.09), yet exposure quartiles Q2-Q4 were all associated with significantly increased myopia risk relative to Q1 (OR range: 1.30–1.58). Subgroup analyses suggested variability across sex, grade level, and parental education, but no consistent pattern was observed. Results were robust after adjusting for ozone and using alternative exposure windows.

Our results provide clear evidence that ambient PM2.5 is an important environmental risk factor for childhood myopia, with a dose-response pattern indicating heightened vulnerability at commonly encountered exposure levels. The consistent risk associated with higher NO2 exposure further supports the role of air pollution. Mitigating myopia burden may therefore require integrating air quality criteria into public health strategies for children’s visual health.

The online version contains supplementary material available at 10.1186/s12886-025-04587-7.