Impacts of climate change on allergic diseases

Introduction Anthropogenic air pollution represents an important class of air contaminants with well-known respiratory health effects in humans. Because of the ubiquity of air pollution in both indoor and outdoor environments, it is reasonable to assume that exposures to aeroallergens rarely occur without co-exposure to one or more air pollutants. This highlights the importance of possible interactions between air pollution and aeroallergens. Such interactions may occur over various scales of space and time, involving mechanisms at the level of individual particles in the atmosphere, via patterns of deposition in the respiratory system, and at the level of the individual immune responses to environmental exposures. Furthermore, air pollution emission, transport, chemical transformation, dispersion, and deposition all are influenced by meteorological factors that are undergoing change in response to climate change. For example, a warming climate will favour higher concentrations of ozone in some locations. On the other hand, actions to mitigate climate change can have profoundly positive impacts on local air quality, leading to substantial health benefits. Here we examine the interactions of air pollution and aeroallergens in the context of a changing climate. We start by reviewing emerging knowledge on how climate change affects air pollution. Then, after briefly reviewing the health effects of air pollution, we examine the small but growing literature on interactions between air pollution and aeroallergens at the levels of exposure, dose, and health effects. Impact of Climate Change on Air Pollution The influence of meteorology on air quality is substantial and well established (Jacob, 2005; Jacob and Winner, 2009; Kinney, 2008). Weather patterns have a profound influence on the concentration of air pollution in the atmosphere through the action of temperature, winds, vertical mixing, and rainfall. Air pollution episodes often occur when atmospheric conditions reduce vertical and/or horizontal dispersion. For example, calm winds and warm air aloft create inversions that limit the vertical dispersion of ground-level pollution emissions in cities. Stable high-pressure systems can allow pollution to accumulate and intensify over large regions. Emissions from power plants increase during heat waves when air-conditioning use peaks. Also, cold temperatures lead to higher emissions from residential fuel combustion (Jung et al., 2010).