PITTSBURGH -- The following is a transcript of a report by Team 4 investigator Jim Parsons that first aired July 20, 2009, on WTAE Channel 4 Action News at 5 p.m.

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We did our research at the state Department of Health. We charted the most recent numbers of school kids in western Pennsylvania diagnosed with asthma and then compared that with 10 years ago.

Check this out:

• In Allegheny County, a 60 percent increase in the rate of school children with asthma.
• In Butler County, a 63 percent increase.
• In Greene County, a 79 percent spike.

Those are the kind of numbers that made us ask, "What's going on?"

On a hot, humid summer day, nine out of 10 kids in western Pennsylvania might jump at the chance to hang at the pool. But the other one in 10 might take a pass. They're the kids for whom the chlorine, the humidity and the allergens are triggers.

Cameron Short: "Sometimes I have to stop and I feel like people just want to scream at me, but they don't know I have asthma."

Cameron Short and his sister, Mekayla, are among the more than 20,000 school children in Allegheny County diagnosed with asthma -- and that's a number that has never been higher.

In 1997, 7 percent of school kids in Allegheny County were diagnosed with asthma. By school year 2006, the asthma rate had climbed to 11.3 percent of all kids. That's higher than the national average of 8.9 percent of children with asthma.

And for kids in some individual school districts, the numbers are even higher still, according to a Children's Hospital study.

Dr. Fernando Holguin, Children's Hospital of UPMC: "Children's did a survey not too long ago that suggests as high as 25 percent of children with asthma, which is extremely high compared to the national average."

Dr. David Skoner, Allegheny General Hospital: "If you go into some schools locally here -- and I've gone into many of them, chatted with nurses and principals and so on -- some of the schools claims or report that 50 percent of their population has asthma."

That's a lot of kids with asthma. But what's unique about Pittsburgh that's causing numbers here to climb so dramatically? Experts say it could be a lot of things -- diesel exhaust on school buses, obesity, drastic climate changes, and modern air-tight home construction that doesn't allow fresh air to get in.

But mostly, they say...

Dr. Bruce Dixon, Allegheny County Health Department: "I think it has to do with our air quality, to be perfectly honest."

Skoner: "Number one that comes up on the radar screen is pollution."

But how can that be? Fifty years ago, Pittsburgh's steel mills pumped out so much pollution that street lights came on in the middle of the day, and fewer people had asthma back then.

Dr. Fred Harchelroad, Allegheny General Hospital: "When the smokestacks were belching out all that black stuff, a lot of that particulate matter was actually pretty large that would get filtered out in your nose. It wouldn't even make it into your lungs."

And today's smokestacks emit particles that are so small, they bypass the filters and go straight to the lungs. So why isn't more being done to reduce particle pollution -- especially in the Clairton area, which has the worst air in the nation, according to the American Lung Association?

Dixon: "We want to reduce them to the lowest possible level we can without having a major impact on industry. I can't give you the air of Montana. Actually, I could, but then we wouldn't have any industry and nobody would be employed."

The county's chief public health official says the asthma problem among children isn't his to solve.

Dixon: "I really think reducing the numbers becomes the duty and the obligation of the health care providers."

But providers don't have the power to regulate air pollution. The health department does.

Still, the hospitals say they're trying to help. Children's Hospital, with funding from the Heinz Endowment, is preparing to launch a $5 million study in search of the causes of high asthma rates among kids -- especially in the Mon Valley.

But it's not enough.

Holguin: "I think we need more awareness and more publicity."

There is some good news among the bad. Treating asthma has never been more effective.

Skoner: "We have a better disease understanding and we have therapies that are unprecedented."

Those therapies include treating asthma with steroids every day, not just on the days when it's hard to breathe. And yet, 60 percent of asthma patients still don't do it.

Skoner: "The large reason it hasn't happened is some of the doctors don't use the guidelines that we have to practice -- and even when they do, patients don't follow the recommendations to use anti-inflammatory controller medicine on a daily basis."

And there are steps that schools and parents can take to reduce kids' exposure to asthma irritants. By law, parents have the right to tell the district they want to be notified before any pesticides or fertilizers are applied to school property.

And regarding diesel fumes, millions in federal and state funds are now available to help pay for diesel exhaust control devices on school buses in Allegheny County.

But in the end, only local, state and federal regulators can control how much air pollution we're breathing. And small particle pollution, as you heard, is the No. 1 trigger for asthma.