"It's a very potent greenhouse gas," said Eric Davidson, the president of Woods Hole Research Center. "It's about 300 times more potent per molecule as carbon dioxide."
He added, "Its half-life is over 100 years. The emissions of that gas will be with us through many generations."
The subsequent increase in temperature only makes matters worse. Nitrous oxide is also a precursor to ozone and nitrogen dioxide. Ozone in the stratosphere is a good thing. These molecules block some of the ultraviolet rays that heat the Earth. However, ozone close to the surface is a harmful irritant, triggering asthma, reducing lung capacity and affecting immune system response.
Over the next few decades, these health risks are expected to increase substantially. Longer summers will intensify the amount of ozone in the air, and more frequent droughts will hinder air circulation, keeping the toxin at unsafe levels for longer periods of time. In San Joaquin County, a five-week dry spell last winter wreaked havoc with Central Valley air quality.
"Oh, my God, it was dreadful. The air was just not being replenished," Lighthall said. "You have slow air speeds; you have a lot of photooxidization, sunlight-induced excitation of the molecules."
Such an issue isn't uncommon in the San Joaquin Valley. The region has had almost 100 ozone violations this year -- meaning the amount of ozone in the air tops federal limits.
The downside of nitrogen fertilizer
Farmers administer nitrogen to their fields as a crop booster. Without it, San Joaquin County wouldn't be the agricultural giant it is today, and the world would be unable to feed its growing population. However, it's not uncommon for more than half the nitrogen fertilizer to dissipate into the air and water, according to one of the studies.
Agricultural activities in the United States account for almost half a million tons of nitrous oxide, the vast majority of nationwide production of the gas, said U.S. EPA. Another source of atmospheric nitrogen is San Joaquin County's booming transportation industry, which carries its agricultural products across the nation.
"We have to use nitrogen to grow food; it's inadvertently produced when we burn fossil fuels," Davidson said.
That doesn't bode well for teens like Casandra who already have asthmatic conditions. Asthma accounts for one-quarter of all emergency room visits -- 1.75 million of them -- in the country each year, the CDC said. There's no easy solution for people who can't change their living situations.
"Reduce the amount of air pollution in the air or come up with adaptive measures to reduce your exposure, and that could include staying inside," said Jennifer Peel, an associate professor at Colorado State University. "It doesn't make sense to tell our kids to stay inside. It's not a good public health message."
And Robbi Cabrera, Casandra's mother, says she couldn't keep her daughter indoors even if she wanted to. Casandra plays basketball, volleyball and softball. She also rides horses. Even as the temperatures climb and ozone levels peak, Robbi Cabrera added, kids will be kids. But that doesn't mean an active outdoor lifestyle is without cost.