Patella et al. Clin Mol Allergy (2018) 16:20 https://doi.org/10.1186/s12948-018-0098-3 Clinical and Molecular Allergy REVIEW Open Access Urban air pollution and climate change: “The Decalogue: Allergy Safe Tree” for allergic and respiratory diseases care Vincenzo Patella1,2,3*† , Giovanni Florio1,2†, Diomira Magliacane1†, Ada Giuliano4†, Maria Angiola Crivellaro3,5†, Daniela Di Bartolomeo3,6†, Arturo Genovese2,3†, Mario Palmieri3,7†, Amedeo Postiglione3,8†, Erminia Ridolo3,9†, Cristina Scaletti3,10†, Maria Teresa Ventura3,11†, Anna Zollo3,12† and Air Pollution and Climate Change Task Force of the Italian Society of Allergology, Asthma and Clinical Immunology (SIAAIC) Abstract Background: According to the World Health Organization, air pollution is closely associated with climate change and, in particular, with global warming. In addition to melting of ice and snow, rising sea level, and fooding of coastal areas, global warming is leading to a tropicalization of temperate marine ecosystems. Moreover, the efects of air pol- lution on airway and lung diseases are well documented as reported by the World Allergy Organization. Methods: Scientifc literature was searched for studies investigating the efect of the interaction between air pollu- tion and climate change on allergic and respiratory diseases. Results: Since 1990s, a multitude of articles and reviews have been published on this topic, with many studies con- frming that the warming of our planet is caused by the “greenhouse efect” as a result of increased emission of “green- house” gases. Air pollution is also closely linked to global warming: the emission of hydrocarbon combustion products leads to increased concentrations of biological allergens such as pollens, generating a mixture of these particles called particulate matter (PM). The concept is that global warming is linked to the emission of hydrocarbon combustion products, since both carbon dioxide and heat increase pollen emission into the atmosphere, and all these particles make up PM10. However, the understanding of the mechanisms by which PM afects human health is still limited. Therefore, several studies are trying to determine the causes of global warming. There is also evidence that increased concentrations of air pollutants and pollens can activate infammatory mediators in the airways. Our Task Force has prepared a Decalogue of rules addressing public administrators, which aims to limit the amount of allergenic pollen in the air without sacrifcing public green areas. Conclusions: Several studies underscore the signifcant risks of global warming on human health due to increas- ing levels of air pollution. The impact of climate change on respiratory diseases appears well documented. The last decades have seen a rise in the concentrations of pollens and pollutants in the air. This rise parallels the increase in the number of people presenting with allergic symptoms (e.g., allergic rhinitis, conjunctivitis, and asthma), who often require emergency medical care. Our hope is that scientists from diferent disciplines will work together with institu- tions, pharmaceutical companies and lay organizations to limit the adverse health efects of air pollution and global warming. *Correspondence: [email protected] †All authors contributed equally to this manuscript 1 Division Allergy and Clinical Immunology, Department of Medicine ASL Salerno, “Santa Maria della Speranza” Hospital, Battipaglia, Salerno, Italy Full list of author information is available at the end of the article © The Author(s) 2018. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creat​iveco​mmons​.org/licen​ses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creat​iveco​mmons​.org/ publi​cdoma​in/zero/1.0/) applies to the data made available in this article, unless otherwise stated. Patella et al. Clin Mol Allergy (2018) 16:20 Page 2 of 11 Background decrease during spring and summer when pollen concen- Climate change is already underway and is expected to trations are typically highest [13]. continue in the next decades: temperatures are increas- Some particulates are naturally occurring and originate ing, global precipitation patterns are changing, ice and from volcanoes, dust storms, forest and grassland fres, snow are melting, and global average sea level is ris- living vegetation, and sea spray. Although most aerosols ing. Moreover, the impact of global warming on human remain suspended in the atmosphere for short periods health has been documented by several reports from (typically between 4 days and a week), they can travel the World Health Organization (WHO) [1], which illus- vast distances. Dust plumes from the Sahara often cross trate that a major concern about this phenomenon is the Atlantic and reach the Caribbean. Winds sweep a the increase in air pollution levels. In this respect, the mixture of Asian aerosols, including dust from the Gobi last report of the European Environment Agency (EEA) desert and pollution from China, to the east over Japan indicates that up to 96% of the urban population in the and toward the central Pacifc Ocean. Smoke from wild- European Union are exposed to particulate and fne dust fres in Siberia and Canada can go as far as the Arctic ice levels in excess of threshold values [2]. In addition to air cap [11]. Sea spray from the Mediterranean Sea and min- pollution produced by hydrocarbon combustion emis- eral dust from Sahara in North Africa can contribute to sions, there is another issue: the formation of particles the chemical composition of PM in Southern Europe [14, related to global warming, and the presence of gases, 15]. such as ozone, with generation of a mixture of particles Human activities, including the combustion of fos- in the atmosphere, called particulate matter (PM) or sil fuels in vehicles, power plants, and many industrial particle pollution. Environmental PM is a heterogene- processes [10], can also generate signifcant amounts of ous mixture of particles produced by various processes, particulates. Coal combustion in developing countries is whose size ranges from 2.5 to 10 μm. Te fne particulate the primary means to generate energy and heat homes. fraction (PM2.5) (also known as “fne particles”) consists Although salt spray is the most common form of partic- of particles with a size of 2.5 microns (or smaller), while ulate in the atmosphere over the oceans, anthropogenic the ultrafne particulate fraction (also known as “ultrafne aerosols, i.e. those that are generated by human activities, particles”) consists of particles with a size smaller than currently account for about 10% of the total mass of aero- 0.1 μm. Te latter has a variable chemical composition, sols in the atmosphere [11]. with the highest volatility, which is obviously due to its In recent years, air quality has improved in industrial- smaller size. It should also be noted that, although the ized Western countries, while it has worsened in devel- ultrafne fraction represents less than 1% of the particu- oping countries. In Asia, for example, anthropogenic late mass, it is suspected of causing the greatest harm to emissions have increased in recent decades with the the exposed population [3–6]. Importantly, this particu- rapid development of urbanization and industrializa- late fraction can reach the deepest parts of the bronchial tion. On the contrary, aerosol emissions have declined tree, leading to major infammatory and procarcinogenic in North America and Europe with the relocation of fac- efects on the bronchial mucosa [6]. Of note, PM is also tories to developing countries and with the adoption of involved in other diseases, including cardiovascular dis- more stringent clean air regulations in Western coun- orders such as coronary heart disease and heart failure. tries. However, it may be difcult to defne the amount Tese conditions are mainly due to the oxidative stress of air pollution in diferent areas of the world, since most generated by the infammatory response, with both short- aerosols remain suspended in the atmosphere for short and long-term adverse efects on human health through periods, typically between 4 days and a week. PM parti- a variety of mechanisms [7–11]. In addition, it has been cles in the atmosphere can move at 5 m (16.4 ft) per sec- demonstrated that exposure to ozone and PM2.5 induces ond, and may travel thousands of kilometres in a week, adverse health efects, including various pulmonary dis- making it difcult to accurately measure pollution levels; eases and lung cancer. Overall, air pollution-related consequently, any predictions about the deterioration of global mortality has been associated with several emis- air quality can be distorted by this initial bias, especially sion sources; therefore, air pollution control can be an with regard to time. efective strategy to reduce mortality [12]. Both concen- trations and chemical composition of PM show a large Air pollution and climate change‑related health impacts variability not only geographic, but also seasonal. PM Global warming is a major public health emergency. concentrations are usually higher in urban areas than in Global temperature has risen markedly over the last rural areas. With regard to seasonal variability, PM levels 50 years and is still rising, as demonstrated by warm- increase signifcantly during the winter due to increased ing of the oceans, rising sea levels, melting of glaciers, emissions from road trafc and residential heating, and retreating of Arctic sea ice, and diminishing snow cover Patella et al. Clin Mol Allergy (2018) 16:20 Page 3 of 11 in the Northern Hemisphere. Climate change is also claim that thunderstorms can concentrate pollen grains associated with extreme weather events such as heat at ground level which rupture due to osmotic shock and waves, droughts, foods, and hurricanes.