Increased Urban Ozone in Heat Waves due to Temperature-Induced Emissions of Anthropogenic Volatile Organic Compounds

Urban ozone (O₃) pollution correlates with temperature, and higher O₃ often occurs during heat waves, threatening public health. However, limited data on how anthropogenic volatile organic compound (AVOC) precursor emissions vary with temperature hinders understanding their impact on O₃. Here, we show that the increase in non-combustion AVOC emissions (e.g., from volatile chemical products) during a heat wave in Shanghai contributes significantly to increased O₃, based on ambient measurements, emission testing, and air quality modelling. AVOC concentrations increase ~2× when the temperature increases from 25 °C to 35 °C due to air stagnation and increased emissions. During the heat wave, higher concentrations result in an 82% increase in VOC OH reactivity. Air quality simulations reveal that temperature-driven AVOC emission increases account for 8% (1.6 s^-1) of this reactivity increase and enhance O₃ by 4.6 ppb. Moreover, we predict a more profound (2×) increase in OH reactivity of oxygenated VOCs, facilitating radical production and O₃ formation. Enhanced AVOC emissions trigger O₃ enhancements in large cities in East China during the heat wave, and similar effects may also happen in other AVOC-sensitive megacities globally. Reducing AVOC emissions, particularly non-combustion sources, which are currently less understood and regulated, could mitigate potential O₃ pollution in urban environments during heat waves.