Research has shown that pollen production has risen in tandem with carbon dioxide over the last few decades. According to Leonard Bielory, a Rutgers University allergy and immunology expert who has been monitoring pollen counts in New Jersey for 27 years, the pollen count has doubled in the past five years. He believes the pollen count could increase by 20% to 30% by 2020.
Additionally, natural events can exacerbate the problem by soaking the ground with extra water, he says. For example, Superstorm Sandy contributed to record pollen counts in the Northeast in April.
Unsurprisingly, more Americans have been testing positive for allergies than ever before. According to testing service Quest Diagnostics, there was a 15% increase in ragweed sensitivity from 2005 to 2009.
Meanwhile, asthma has become so pervasive that the U.S. Environmental Protection Agency has deemed it a "national epidemic." Federal data show that the number of asthma sufferers grew by 17% from 2001 to 2012. Today, one in every 12 Americans—56 million, overall—has been diagnosed with asthma.
Moreover, although not all Americans suffer from allergies or asthma, all end up paying its indirect costs. "There are substantial costs to the health care system (from allergic conditions) that we all carry," CDC's George Luber told USA Today.