Government report provides the science behind extended allergy season

WASHINGTON — The Obama Administration on Tuesday unveiled the Third U.S. National Climate Assessment, a scientific report about climate changes that are happening now in the United States and how they are impacting the nation's health, with longer allergy seasons, for example.

"Climate change, as well as increased CO2 by itself, can contribute to increased production of plant-based allergens," the report noted. "Higher pollen concentrations and longer pollen seasons increase allergic sensitizations and asthma episodes, and diminish productive work and school days. Simultaneous exposure to toxic air pollutants can worsen allergic responses. Extreme rainfall and rising temperatures also can foster indoor air quality problems, including the growth of indoor fungi and molds, with increases in respiratory and asthma-related conditions."

Ragweed pollen season length has increased in central North America between 1995 and 2011 by as much as 11 to 27 days in parts of the United States and Canada in response to rising temperatures, the report suggested. Increases in the length of this allergenic pollen season are correlated with increases in the number of days before the first frost. The largest increases have been observed in northern cities. In 2012, a warm winter leading to early pollen production among trees and plants, followed by hot, dry, low-humidity conditions through the spring and summer contributed to wide circulation of aeroallergens and a severe allergy season, according to reports from physicians. 


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