Greenhouse gases, like CO2, have been linked to warming trends across the globe. With increased durations of warmer weather, plants not only have longer growing seasons (and therefore pollen seasons), but agricultural growing zones will be slowly climbing north, allowing trees and plants to move into the zones they don’t currently inhabit, but that have become too warm for growing food crops.
According to an April 14 news item from Reuters, citing a joint Asthma and Allergy Foundation and National Wildlife Federation report, the impact of continued global warming may include higher allergen levels for longer periods in the eastern part of the US. Currently, the costs in the US associated with allergies and allergic asthma are at $32 billion, which includes direct medical care, lost workdays, and lower work productivity.
Plants that are already highly allergenic, such as ragweed, would not only grow and pollinate for longer, but could produce more allergenic pollen proteins as a result. A researcher comments in the news item that there is evidence that ragweed actually grows faster in higher concentrations of atmospheric CO2 and that poison ivy produces a different, more allergenic form of its allergen, urushiol.
(For more on this topic, see the open-access review article by Shea et al. from our September 2008 issue.)
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