Environment/Climate Change
The Influence of Temperature in Age-Specific Mortality Associated with Ozone Exposure Satbyul Estella Kim* Satbyul Estella Kim
The convergence of rising temperatures, increasing ozone levels, and a significantly aging population presents multiple threats to public health in Japan. Thus, this study investigated the influence of temperature on the mortality effects associated with ozone exposure across all regions in Japan (Hokkaido, Tohoku, Kanto, Chubu, Kansai, Chugoku, Shikoku, and Kyushu and Okinawa) and age groups (0–65, 65–75, and 75 years and above). We performed a two-stage analysis to examine the short-term associations between ozone exposure and mortality at different temperature levels across 47 prefectures, with a focus on the warmer months (June–September) from 2009 to 2019. First, we estimated the prefecture-specific associations using a comprehensive nationwide time-series dataset with a distributed lag nonlinear model. Subsequently, we used a multivariate meta-regression model to determine regional and national associations. A 10-ppb rise in ozone levels nationwide was significantly associated with a 0.44% (95% confidence interval [CI]: 0.26, 0.62) increase in all-cause mortality during the warmer months. Despite the heterogeneity in the degree of estimates, we observed an increasing trend in ozone-related mortality with higher temperature levels in all regions. Our findings from the age group stratification analysis imply that individuals aged 65 and older are more susceptible to ozone exposure with increasing temperature, as evidenced by a statistically significant increase in ozone-related mortality when the temperature reaches the 60th percentile, whereas individuals under 65 years of age show a significant increase at the 70th percentile. The study findings provide an avenue for future research to mitigate the adverse health effects of climate change and air pollution by developing targeted interventions that address the compounded risks of high temperatures and elevated ozone levels, particularly for vulnerable populations such as the elderly, in order to reduce the burden of ozone-related mortality in the context of global climate change.