The study found that, since 1990, pollen seasons lengthened by 20 days and contained 21% more pollen. The researchers attributed roughly half of the lengthening pollen seasons and 8% of the trend in pollen concentrations to climate changes driven by human activity.
Allergy medications can provide relief for many with pollen allergies, said Aaron Bernstein, interim director of Harvard T.H. Chan School of Public Health’s Center for Climate, Health, and the Global Environment (Harvard Chan C-CHANGE), in a February 17, 2021 Verywell Health article. But for others who may be unable to access drugs or who suffer from severe asthma, greater exposure to pollen can be a big problem, particularly when combined with other factors related to climate change, said Bernstein, who was not involved in the study.
For example, he noted that the additional planetary heat that prolongs the growing season—which leads to more pollen—can also cause heatwaves and worsen air pollution, both of which can cause adverse health effects. Global warming can also lead to increases in insect-transmitted diseases, and to increases in insect populations that can kill trees and induce wildfires—which can exacerbate the health effects of asthma and pollen allergies.
“I think this is a smoking gun of the health risk from climate change that is probably clearer than any other,” said Bernstein. “And yet it’s just one signal among many that come from the same warming of the planet.”