PLoS ONE 9, e111712 (2014)

Credit: © PHOTOTAKE INC. / ALAMY

Allergic and asthmatic symptoms following pollen exposure constitute a human health problem that could be accentuated by climate change. Widely distributed, wind-dispersed pollen from grass species are particularly allergenic, so the impacts of climate change on grass pollen are likely to have the greatest human health consequences.

Jennifer Albertine from Harvard University, USA, and co-workers exposed Timothy grass (Phleum pratense) to current and projected atmospheric concentrations of the greenhouse gases CO2 and ozone (O3) to investigate their individual and interactive effects on pollen and allergen production. They found that increased concentrations of atmospheric CO2 increased the amount of grass pollen produced by 50% per flower, regardless of O3 levels. Higher concentrations of O3 reduced the allergen protein (Phlp5) content of the pollen but the net effect, when accounting for CO2-driven increases in pollen numbers, indicates increased allergen exposure. Quantitative estimates based on pollen production and the number of flowering plants per treatment indicate that airborne grass pollen concentrations will increase in the future up to 200%.