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

This study examines how ground-level ozone (O 3 ) 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 O 3 -mortality association, with risks rising sharply above 42.1 μ g/m 3 for cardiovascular diseases; (2) The estimated effects of O 3 on mortality varied across different lag days, peaking on lag03; (3) Respiratory mortality most sensitive to O 3 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 O 3 -related mortality risks across all cause-specific and demographic subgroups. For temperatures below the 25 th , between 25 th and 75 th , and above the 75 th percentiles, a 10 μ g/m 3 O 3 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 O 3 precursor emissions, urgent targeted interventions are needed to protect vulnerable populations from combined O 3 -temperature exposure.