Background  The increasing threats of air pollution and extreme weather have been widely recognized in recent years in China, but their individual and joint effects on cardio-cerebrovascular mortality are unclear.

Objective  This study aims to investigate the individual effects of and potential interactions between oxidant pollutants and ambient temperature on cardio-cerebrovascular mortality risks.

Methods  We collected daily data on death counts of cardio-cerebrovascular diseases, concentrations of ambient air pollutants, and meteorological parameters in Guangzhou, Chinabetween 1 January 2006 and 31 December 2016. A generalized additive model with a Poisson distribution was conducted to assess the associations of oxidant pollutants and ambient temperature with cardio-cerebrovascular mortality risks. Bivariate response surface models and stratified analyses were further adopted to qualitatively and quantitatively examine the potential interactions between oxidant pollutants and ambient temperature on cardio-cerebrovascular mortality risks.

Results  During the study period, the daily averages were 60.3 μg·m⁻³ for ozone (O₃), 50.9 μg·m⁻³ for combined atmospheric oxidant capacity (O_x), 32.5 μg·m⁻³ for nitrogen dioxide (NO₂), and 22.3℃ for ambient temperature. The average daily death counts of coronary and stroke diseases were 20 and 15, respectively. Per 10 μg·m⁻³ increment in O₃, O_x, and NO₂ were associated with increased coronary mortality risks (excess risk, ER) of 1.26% (95%CI: 0.79%-1.74%), 1.61% (95%CI: 0.99%-2.23%), and 1.33% (95%CI: 0.59%-2.07%), and with increased stroke mortality risks of 1.56% (95%CI: 1.04%-2.09%), 2.30% (95%CI: 1.60%-3.01%), and 2.93% (95%CI: 2.07%-3.79%) over cumulative lags of 2-5 days, respectively. The exposure-response relationships between ambient temperature and coronary and stroke mortality risks exhibited an inverse "J" shape, with the minimum mortality at temperatures of 25.7℃ for coronary disease and 27.3℃ for stroke. Our results further showed potentially synergic effects of higher temperatures and higher levels of O₃ and O_x exposures on coronary mortality risks, and the relative ER due to interactions was 0.103 (95%CI: 0.028-0.178) for O₃ and 0.079 (95%CI: 0.004-0.154) for O_x. We didn't find evidence of an interaction between oxidant pollutants and low temperature.

Conclusion  Short-term exposures to oxidant pollutants are associated with increased cardio-cerebrovascular mortality risks, and the interactive effects of high temperature and oxidant pollutants are synergistic in relation to cardio-cerebrovascular mortality risks.