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MIAMI (CBSMiami/AP) – Childhood asthma rates may be leveling off, a new federal study found.

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This means they are no longer increasing.

The study says  the rate of childhood asthma peaked in 2009 with 9.7 percent of all U.S. children having asthma but in 2013, it was down to 8.3 percent.

A possible plateau in childhood obesity rates and declines in air pollution are among factors that may have helped lower cases in kids, the 2001-13 study suggests. Overall, average asthma rates among kids aged 17 and younger increased slightly, then leveled off and declined by the study’s end, when 8.3 percent of kids were affected. Rates varied among some regions, races and ages.

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Researchers found the only sub-group of children whose asthma numbers are increasing are children living in poverty.

The study by the National Center for Health Statistics was published in the journal Pediatrics.

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