In 2019, Durham, NC recorded 1,800 grains of pollen per cubic meter of air, with yellow pollen covering the city and causing severe allergy symptoms like runny eyes, sniffling, and sneezing. If most of the United States had never experienced bad allergies until the 1970s, how did the problem get out of hand so quickly?

Watch the video and learn about different tree “genders” and how the U.S. response to the Dutch elm disease backfired so spectacularly that we actually created the very allergies and asthma that plague us now.