In the middle of the night, Casandra Cabrera stopped breathing. She doubled over in bed, gasping for air. In the panic that followed, her lungs constricted. Her eyes filled with tears. The asthma attack continued for 10 long minutes.

"I keep an inhaler with me everywhere. I have one in my purse, in my sports bag, and in my truck and by my bedside," the San Joaquin Valley, Calif., teenager said. "I've never really imagined life without it. It's kind of normal for me."

It's normal for many children, especially those in California, home to the country's worst air pollution. More than 5 million people in the state have been diagnosed with asthma, which is caused, in part, by contamination from nitrogen compounds, pollutants that stem from the farming and transportation industries.

Climate change is expected to compound the issue, according to a new body of work published in the journal Issues in Ecology. Higher temperatures and an increased risk of drought on the West Coast essentially "cook" the nitrogen, resulting in nitrous oxide and ozone. These nitrogen byproducts cause cardiovascular and respiratory diseases, especially among the region's rural and urban poor who don't have the money to move away and reduce their exposure.

"We have a lot of poverty. This is one of the poorest regions in the country. We have a fairly high fraction of vulnerable people in the population," said David Lighthall, a health science adviser for the San Joaquin Valley Air Pollution Control District. "Kids with asthma aren't getting access to care, and, of course, we have the high levels of exposure. That's a bad combination."

In 2007, about 25 million Americans had asthma, according to the Centers for Disease Control and Prevention. Costs for the chronic disease increased from an estimated $53 billion in 2002 to about $56 billion in 2007. The condition is distinctly prevalent in California's Central Valley, where one out of every six children have asthmatic symptoms -- a contemporary warning of how dire this issue could become in the near future.

Nitrous oxide leads to more ozone
It's not nitrogen gas by itself that's the problem. Eighty percent of the world's atmosphere is made up of the gaseous form. Nitrous oxide is a different story. The combination of nitrogen and oxygen molecules creates a powerful gas. In small quantities, nitrous oxide is used as "laughing gas" in dentist offices. On a larger scale, the vapor traps heat and contributes to global warming.

"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.

"It's tough," Casandra said, "especially when you're involved in sports. It's hard to take in a deep breath, and your lungs feel like they're 10 times smaller."

She added, "You want to work hard, but you can't. You can't breathe."

Major ripple effects
The effects of nitrogen pollution combined with climate change aren't just an issue for humans. Scientists at the Woods Hole Research Center say excess nitrogen can wreak havoc on the environment, causing damaging ripple effects.

What goes up must eventually come down -- often in the form of acid rain. Excess nitrogen corrodes buildings, kills plant species and can harm sensitive crops. Nitrogen that seeps into the water supply causes ocean acidification and destroys coral reefs, a natural barrier that prevents damage to coastal property. It also reduces the oxygen level within the water, asphyxiating marine life.

"Once in the environment, nitrogen cascades from one negative environmental impact to another," according to the study.

The United States has come a long way in reducing nitrogen emissions, mainly by increasing motor vehicle engine standards and regulating power plants, but there's a lot more that needs to be done, Davidson said. Nitrogen reduction has to be a large-scale affair in order to protect the nation's health and its natural resources, he added.

Yesterday, Casandra played a volleyball game -- Linden High School against Amador High School. The match was intense, and by the end of it, she was out of breath. Her mother, sitting on the sidelines, watched her daughter closely for signs of distress.

Outside the gym, ozone concentrations in the Central Valley continued to increase, reaching levels unsafe for people in sensitive groups like Casandra.

Reprinted from Climatewire with permission from Environment & Energy Publishing, LLC., 202-628-6500