Climate Change and Its Effects on Allergic Disease

By Craig Moffat MD

The association between climate change and airborne allergens is coming to light with recent scientific studies. This article outlines some of the key reasons why they are associated.

allergies
Climate change and its effects on the environment is a much discussed and hotly debated issue. No matter what our position, it is interesting to speculate on the effects climate change may have on the nearly 10-20% of earth’s inhabitants who suffer from respiratory allergic disease. A recently published American Academy of Allergy, Asthma, and Immunology Committee Paper examined some of the anticipated effects of climate change relevant to allergies and allergy suffers (Barnes CS, et al. Climate change and our environment: The effect on respiratory and allergic disease. J Allergy Clin Immunol: In Practice 2013;1:137-41).

While difficult to predict, according to this article, some of the anticipated changes that could occur specifically regarding respiratory allergies with climate warming and higher levels of greenhouse gases may include:
  1. Longer pollen seasons, with increased morbidity from respiratory allergies. This view is supported by Scandinavian studies on duration and pollen concentrations associated with birch tree pollination over 20-33 years.
  2. Altered distribution of pollenating plants into new areas, including above former tree lines, leading to broader distribution.
  3. Increased CO2 leading to earlier plant flowering and higher pollen concentrations. Studies indicate with CO2 levels double, ragweed plant pollen production increases 30-90%.
  4. Increased ozone from hot sunny days leading to more symptoms for those at risk for asthma.
  5. Increased mold production with rising sea levels and altered rainfall patterns.
  6. Heightened stinging and biting insect frequencies, especially with population in new areas.
  7. Efforts to improve energy efficiency in home building may lead to superinsulation strategies and reduced exchange of indoor/outdoor air, indoor moisture accumulation, the effects of which may result in increased indoor respiratory allergen exposure and sensitization to dust mites and molds
Although not allergens, indoor air pollutants resulting from tighter homes increase including volatile organic compounds, radon gas, water vapor, smoke particulates and protein allergens. Rising concentrations may enhance the genesis of respiratory allergy problems in persons at risk. Air pollutants including rising ozone concentrations and particulates as well as altered forest fire patterns have been associated with rising prevalence of respiratory disease. Recently more than 12% of Arizona adults in urban Phoenix were told by a health care professional they currently have asthma (typically 5% of the population), and 59% of adults with asthma reported an attack within the past year. Rising air pollutants have resulted in greater “red burn” days due to ozone and particulates in large urban and suburban areas in the valleys of the Rocky Mountains, which in turn is associated with a rising incidence of acute respiratory exacerbations of asthma. Our attempts to mitigate and invoke “green” practices may actually exacerbate the problem, including composting facilities increasing fungal burdens, as well as increased use of biodiesel fuels and wood burning heat sources worsening greenhouse gases and particulates production.

While scientific evidence is emerging of the association between climate change and the environment regarding airborne allergens, our understanding of these effects on the scope and degree of human disease needs further investigation and clarification. While affecting only a portion of the world’s population, the outcomes could be profound in a group who already suffer significantly from the environment.