4. Discussion
In the present study, pneumonia cases resided in the warm climate or warmer climate quartiles were associated with stronger acute mortality effects of air pollution on pneumonia, especially for NO2 air pollution. Our findings indicate that warmer urban climate may worsen the association of pneumonia mortality with air pollution. Our findings were consistent with a few large-scale multicity studies using annual mean temperature or using latitude to represent city climate which suggested that the risk estimates of air pollution were higher in warmer cities (Katsouyanni et al., 2009; Katsouyanni et al., 2001; Kioumourtzoglou et al., 2015). For example, the Air Pollution and Health: A European Approach Phase-2, a large-scale multi-city epidemiological study, examined 29 European cities, and reported that mortality effect of PM10 per 10 μg/m3 increase in ER% was stronger in cities with warm climate (0.82%) than that in relatively cold climate (0.29%) (Katsouyanni et al., 2001). Although few studies have investigated the interaction between climate and air pollution on human health, a great number of epidemiological studies have investigated the modification effects of weather (De Sario et al., 2013; Medina-Ramon et al., 2006; Meng et al., 2012; Sun et al., 2015). Meng et al. (2012) examined eight Chinese cities with a total population of 36.1 million and demonstrated that the risk estimates on high temperature days (N95th percentile) versus normal temperature days (5th–95th percentile) increased by 0.81% for total mortality, 1.01% for cardiovascular mortality, and 0.99% for respiratory diseases per 10 μg/m3 increment in PM10. These findings were based on the short-term modification of weather, instead of urban climate modification where we need to take potential acclimatization into account.
