Does urban asthma exist? How climatic changes and urban air pollution intervene on asthma and respiratory allergy

How bad is living in a city for asthma? Several investigations have indicated that individuals living in cities have a higher risk of suffering from asthma and allergies compared to those living in the countryside, this being due to several factors. Besides the fact that individual susceptibility varies between urban and rural settings, there are environmental factors that are typical of living in a city. First of all, as perfectly indicated by D’Amato in his article, urban air pollution is composed of gases and particles. Whereas industrial pollution has decreased in recent decades, at least in industrialized countries, air pollution related to traffic is rising or remaining at the same level (www.eea.org). Gases and particulate matter have been shown by experimental and epidemiological studies to be involved in respiratory adverse effects. At the population level, not only can short-term exposure to elevated concentrations of urban air pollutants exacerbate pre-existing asthma and allergic rhinitis but also long-term exposure to these pollutants can be responsible for adverse effects, including asthma and the development of allergies [2]. Most investigations reporting long-term effects of air pollution have considered exposure to background air pollution as assessed by monitoring stations, which provide an under-estimation of the real exposure to these pollutants. Fewer studies have considered a more robust assessment of the individual’s exposure to air pollution so avoiding miss-classification of exposure. Among them, very recently, is the French 6 Cities study in which long-term average exposure to major urban air pollutants, including benzene, volatile organic compounds (VOCs), sulfur dioxide (SO2), particles with an aerodynamic diameter of 10 μm or less (PM10), nitrogen dioxide (NO2), nitrogen oxides (NOx), and carbon monoxide (CO), was assessed using a dispersion model capable of capturing small-scale variations in 6,683 children. These children underwent clinical examinations, including lung function and skin prick tests, and their parents completed questionnaires on asthma and aller-