Evidence on the association between ambient ozone (O(3)) exposure and attention-deficit/hyperactivity disorder (ADHD) in children was limited and inconsistent. To address this gap, we conducted a large-scale study involving 179,661 school-aged children across 14 cities in three regions of China between 2012 and 2018. ADHD symptoms were assessed using parent-reported Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition criteria. A well-validated spatiotemporal model at 1 × 1 km resolution was employed to estimate four-year average O(3) concentrations at each participant's home and school addresses. We applied generalized linear mixed models adjusted for a range of potential confounders to examine the associations and explore potential effect modifiers. The prevalence of ADHD symptoms was 5.8 %. Higher O(3) exposure was positively associated with ADHD symptoms. Specifically, the odds ratio of ADHD symptoms was 1.24 times greater (95 % confidence interval [CI]: 1.21, 1.26) per interquartile range (7.0 µg/m(3)) increment in home-school O(3) concentration. The association was similar after adjustment for other air pollutants and greenness, as well as in sensitivity analyses. Notably, regional heterogeneity was observed, with a stronger association in the southeastern region. Additionally, larger estimates of O(3) were found among older children and those exposed to low temperature, low humidity, and low greenness. Our findings from the largest study in China to date provide compelling evidence that long term exposure to O(3) is associated with an increased risk of ADHD symptoms in children, highlighting the need for public health policies to mitigate O(3) pollution for the protection of child neurodevelopment.
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