Dear EarthTalk: Is it true that asthma rates in the U.S. have doubled in the last three decades? What's behind this troubling trend and what can we do to reverse it?

 
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Dear EarthTalk: Is it true that asthma rates in the U.S. have doubled in the last three decades? What's behind this troubling trend and what can we do to reverse it?--Patrick, via e-mail

Asthma is on the rise across the U.S., doubling since the 1980s. According to the Environmental Defense Fund (EDF), most people who develop asthma likely have a genetic predisposition but also probably experienced "critical environmental exposures during the first years of life." Asthma rates are highest in urban areas where auto and industrial emissions make for difficult breathing. But air quality in U.S. cities has improved in the last few decades, leaving researchers puzzled as to what's behind the trend.

One theory is that better hygiene in developed countries means that Westerners have less exposure to bacteria, viruses and parasites, altering our immune response with the result being increased risk for allergic diseases like asthma. Indeed, Western asthma rates are 50 times higher than in rural Africa. While this "hygiene hypothesis" may be part of the story, researchers believe that there are also other factors.

Some studies have shown a correlation between asthma and obesity, though a direct link is hard to prove. Other research has shown that psychological stress can trigger asthma attacks in those already predisposed. Dr. Harold Nelson, professor of medicine at the National Jewish Health in Denver, explained in a 2009 New York Times blog post that increased acetaminophen (i.e. Tylenol) use in young children, exposure to household cleaning sprays, and lack of Vitamin D also likely contribute to rising asthma rates. But how?

Pediatricians recommend against giving young children aspirin today, given the increased risk of Reye's syndrome, so many parents now use acetaminophen to relieve pain and reduce fever. But acetaminophen lowers levels of the antioxidant glutathione, resulting in an...

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