Concurrence of heatwaves and extreme ozone episodes and impact on health and well-being

Abstract

Climate change and air pollution are universal related problems and their combined monitoring, at national, regional and local scales, is a worldwide primary public concern. Industrial and traffic activities emit various pollutants that are harmful to health, among which we count ozone (O3) which concentrations may be accentuated under the influence of sunny days. Ozone in the air we breathe can cause respiratory diseases and can trigger a variety of health problems including chest pain, coughing, throat irritation, and airway inflammation. It can also reduce lung function and harm lung tissue. People most at risk include people with asthma, children, older adults, and people who are active outdoors. Temperature is the first meteorological factor to be directly involved in leading to ozone extreme events. In Morocco, the cities of Casablanca and Marrakech are metropolises whose rate of urbanization and population density are the highest in the country, they concentrate many large industrial units and a large vehicle fleet generating pollution. Urban and atmospheric conditions in both cities make them vulnerable to climate change extremes and air pollution episodes that may directly affect population health and wellbeing. In the context of global climate change, more frequent and/or persistent heatwaves and extreme ozone episodes are likely to occur during the next decades and a key question is about the concurrence of these extremes and their joint effect on human health. In this work, using surface temperature and ozone observations during extended summers (April-September), between 2009 and 2016, in Casablanca and Marrakech, we evaluate the thermal comfort and air quality health indexes related to concurrent heatwaves and ozone episodes in order to assess their impact on health and wellbeing. We show that the extremes in temperature and ozone cluster together in many cases and cause the two indexes to worsen.