What's making American children sick has changed drastically over the past 50 or so years. Time Warner Cable News Health Reporter Erin Billups takes a look at the changing environment and things you can do to protect your children, in this next installment of our Fit Kids coverage.

Polio, measles and yellow fever are just some of the diseases of the past that used to ravage children in the United States.

Now the challenges are different, the common diseases affecting kids are chronic and there's growing evidence that they're a product of our changing environment.

"But at the same time as we've controlled those infectious diseases, we've allowed our children to be exposed to more and more and more chemicals. Sometimes these chemicals cause acute disease, like acute lead poisoning. More often, they make children chronically sick,” said pediatrician Dr. Philip Landrigan, who heads up Mount Sinai's Children's Environmental Health Center.

Dr. Landrigan has been studying the impact of air pollution and commonly used chemicals in commercial products like pesticides, PCBs, brominated flame retardants, lead, phthalates and bisphenol A.

"They provoke asthma, they cause silent brain injury, which reduces a child's IQ, or shortens a child's attention span, or pushes up the risk for autism,” said Dr. Landrigan
Exposure to these toxins may just be a part of the problem, but take a look at the stats.

The number of Americans with asthma has grown nearly 15 percent over the last decade: one in 11 kids have asthma.

And in New York City it's a huge problem. As of 2012, 13 percent of kids 12 and younger have been diagnosed asthma.

In 2000, one in 150 children had Autism Spectrum Disorder, in 2010 it was one in 68.

The percentage of children diagnosed with Attention Deficit Hyperactivity Disorder went from nearly eight percent in 2003 to 11 percent in 2011.

"Every IQ point matters and if a child loses intelligence due to lead or some other chemical, you can never get it back,” said Dr. Landrigan

Dr. L says it's a consequence of reactive rather than proactive regulations.

"A big problem in this country is we allow chemicals to come onto the market with no safety testing. We presume they are innocent before proving guilty,” said Dr. Landrigan.

Beyond lobbying state and federal lawmakers for change, there are practical ways to protect your kids. We'll have more on that in tomorrow's Fit Kids February piece, where we'll also give you the rundown of what our coverage will look like over the next month.