A Perfect Storm
Thunderstorm asthma — a rare event in which raindrops break pollen grains into particles tiny enough to be inhaled — can be deadly.
The wind and fast-moving rain mixed with pollen from seed plants allow the fragmented particles to bypass the body’s natural defense systems and find their way into the lungs.
Cities from Atlanta to Australia have experienced this phenomenon in recent years. In the most recent incident in November in Sydney, Australia, thousands of people flooded emergency rooms struggling for breath and several died.
Stefanie Sarnat, associate professor of environmental health at Emory, has studied the occurrence in Atlanta. She says it most often strikes in areas with high humidity when specific conditions are met, such as compromised air quality (like increased pollen) and a large population that is susceptible to asthma. A small increase (about 3%) in ER visits for asthma occurs after every thunderstorm, Sarnat adds, because asthma sufferers’ symptoms are inflamed, but large-scale outbreaks are rare.
"In thunderstorm asthma, stormy winds and moisture can cause the pollen to rupture into tiny particles, small enough to be inhaled."— Dr. Jennifer Shih
Thunderstorm asthma usually affects people with an allergy to grass pollens, says Jennifer Shih, an Emory physician and medical director of the pediatric allergy clinics. It can be worse in those that also have asthma. In fact, in one study that looked at an earlier event in Australia in 1997, 96% of those affected proved sensitive to grass pollen upon testing. "This phenomenon is literally the culmination of a perfect storm," Shih says. "Grass pollen is usually too large to enter the small airways of the lungs and is filtered out by the nose. In thunderstorm asthma, stormy winds and moisture can cause the pollen to rupture into tiny particles, small enough to be inhaled. The outflow winds of a thunderstorm can then concentrate these tiny particles at ground level, where people breathe them in and they cause an acute asthma attack in those who are allergic to grass pollens."