Impacts of climate change on aeroallergen production and atmospheric concentration

Introduction Climate change is the issue of our time. It is global, international, and pervasive. Of all the impacts of climate change, those on human health are perhaps the most significant. Indeed, the prestigious medical journal The Lancet recently stated that ‘Climate change is the biggest global health threat of the 21st century’ (Costello et al., 2009). The impacts of climate change on human health are many and varied. Beyond what are thought of as the direct impacts on human health, such as the direct effects of temperature extremes and severe weather, are a multitude of indirect impacts of climate change on human health, or what Butler (2014) has recently described as secondary (and tertiary) effects. The UN Intergovernmental Panel on Climate Change (IPCC) has most recently described these indirect or secondary impacts on human health as ‘ecosystem-mediated impacts’ (Smith et al., 2014). The impacts of climate change on allergic diseases fall clearly within this realm. Allergic diseases, such as asthma and allergic rhinitis, are of global importance for a number of reasons. It is estimated that 235 million people currently suffer from asthma, this being the most common non-communicable disease among children (World Health Organization, 2015). The prevalence of allergic diseases has increased dramatically over recent decades and continues to increase (Pearce et al., 2007). And allergic disease markedly affects the quality of life of both individuals with this disease and their families and negatively impacts the socioeconomic welfare of society (Pawankar et al., 2011). Our environment contains allergens from many sources. These include pollen from trees, weeds and grasses, mould spores, house dust mites, cockroaches, and others. Climate plays a major role in the lives of allergenic organisms, as well as their production of allergens and our eventual exposure to such allergens. Climate influences the distribution and abundance of all allergenic organisms. Similarly, the variations in temperature, precipitation, humidity, and other factors that characterise the seasons control the activities of allergenic organisms, including their production of allergens. The so-called pollen season is perhaps the best known example of this.