Abstract

Antibiotic resistance genes (ARGs) in PM 2.5 have received great attention due to their potential risks to human health and ecological balance. The distribution and abundance of ARGs are known to be influenced by various environmental factors. However, the effect of ozone—a major atmospheric pollutant—on the abundance of ARGs in PM 2.5 remains poorly understood. In this study, we show that as ozone pollution levels increase, the abundance of eight typical ARGs in PM 2.5 collected from four monitoring sites across three representative cities in China's Jianghuai region generally decreases. Notably, tetW , sul1 , and blaTEM genes exhibit the most substantial reduction in abundance, demonstrating the highest sensitivity to ozone. Ozone affects the abundance of these three ARGs through both vertical and horizontal gene transfer, but with differing mechanisms. For vertical gene transfer, ozone reduces the abundance of these sensitive ARGs by inhibiting potential bacterial hosts. The identity of these potential hosts varies depending on the type of ARG and the sampling location. For horizontal gene transfer, ozone diminishes the abundance of tetW and blaTEM genes by reducing the abundance of mobile genetic elements. In contrast, the guanine-rich and ozone-responsive sul1 gene is primarily decreased through ozone-driven efficient degradation of extracellular sul1 . These findings advance our understanding on the interactions between atmospheric pollutants and antibiotic resistance, providing a theoretical foundation for accurately assessing their human exposure risks.