The modification effect of temperature on the association between ozone and human mortality in Shanghai, China

This study examines how ground-level ozone (O3) exposure affects mortality in Shanghai (2013–2018), and how temperature modify this relationship in subtropical climate. Using a generalized additive model, we found: (1) A significant non-linear O3-mortality association, with risks rising sharply above 42.1 μg/m3 for cardiovascular diseases; (2) The estimated effects of O3 on mortality varied across different lag days, peaking on lag03; (3) Respiratory mortality most sensitive to O3 exposure compared with total non-accidental or cardiovascular mortality; (4) Higher vulnerability among females, adults ≥60 years, and those with low-education; and (5) Consistent effect modification by temperature, both low- and high-temperature strata have elevated O3-related mortality risks across all cause-specific and demographic subgroups. For temperatures below the 25th, between 25th and 75th, and above the 75th percentiles, a 10 μg/m3 O3 increase was associated with 0.97% (95% CI: 0.64–1.31%), 0.73% (0.30–1.16%), and 0.85% (0.38–1.32%) rises in total non-accidental mortality, respectively. Given ongoing climate change and rising O3 precursor emissions, urgent targeted interventions are needed to protect vulnerable populations from combined O3-temperature exposure.