Extreme heat is identified as a key climate change risk in Europe in the near and long term (EEA, 2017; Kovats et al., 2014). Extreme heat increases the rates of death (mortality) and can exacerbate a range of diseases (morbidity). In particular, heat increases mortality and morbidity for cardiovascular and respiratory dis-eases (CVD and RD), which together constitute cardiopulmonary diseases (CPD) (Basu, 2009; Turner et al., 2012). Increases in heat-related mortality are projected to outweigh reductions in cold-related mortality, and increasingly so with greater degrees of warming (Ebi et al., 2018).
The health effects of extreme heat are interlinked with air pollution in several ways. Air pollution is currently the largest environmental killer in Europe, causing ~500,000 premature deaths annually (EEA, 2016; Im et al., 2018). Previous studies indicate that there may be synergistic effects of extreme heat and air pol-lution on CPD outcomes (Burkart et al., 2013). Moreover, extreme heat may increase air pollution levels, which is linked to large-scale (synoptic) meteorologcal features (Schnell and Prather, 2017). Modelling and observational studies suggest that especially surface ozone (O3) and fine particulate matter (PM2.5) increase in many populated regions as temperature increases, even when emissions of air pollutants are not increasing (Krasnov et al., 2013; Otero et al., 2016). O3 and PM2.5 are two major air pollutants that increase the risk to human health and CPD in particular (WHO, 2013).
The risk of wildland fires increases during periods of extreme heat and decreasing precipitation (Kovats et al., 2014). Wildland fires cause intense air pollution (Baker et al., 2016) and PM2.5 exposure due to wildland fire emissions is already an important contributor to mortality in Europe (Kollanus et al., 2017). Elevations in CPD mortality during wildfires appear to be larger than what would be expected from the increased pollution levels only (Analitis et al., 2012; Faustini et al., 2015). In an increasingly warming world, episodes of ex-treme heat and high levels of PM2.5 and O3 are likely to occur simultaneously, could occur more often, last longer, and become more intense ? causing increasing health risks.
CPD is highly prevalent in Europe and increases with an ageing population. In 2016, cardiovascular dis-eases alone accounted for 52% and 60% of deaths in Central and Eastern Europe respectively, and for 34% in Western Europe. Chronic respiratory diseases accounted for an additional 3% - 8% of total deaths across Eu-rope (IHME, 2017). The current cost of CVD and RD in total in EU is estimated at nearly €600 billion (ERS, 2018; ESC, 2018)). This means that environmental stressors that adversely affect CPD may bring ill health to a large number of Europeans and could have a substantial socio-economic impact.
The vulnerability to heat stress may differ widely among population groups due to complex causal pathways and differential vulnerability associated with contextual and individual factors. Excess mortality during extreme temperature events is largely preventable to the extent that adaptation measures can be tailored to alleviate contextual and individual vulnerability factors or otherwise mitigate the risks to vulnerable populations. To develop climate change adaptation policies, a detailed understanding of the predominant vulnerability factors in different communities and regions is needed.