CHICAGO (AP) — Experts are cautiously welcoming the results of the latest government study on childhood asthma.

The study published online in the journal Pediatrics finds that after going up for decades, asthma rates in U.S. children have quieted down.

The 2001-13 study suggests that a possible plateau in childhood obesity rates and declines in air pollution are possible factors.

Overall, average asthma rates among kids aged 17 and younger increased slightly, then leveled off and declined by the study’s end.

In most recent years, there was a decrease among Hispanic children, children younger than 5, those in the Midwest, and those from families of middle to upper class. Rates plateaued among whites and those living in the Northeast and West.

Asthma rates increased in those aged 10 to 17, kids from lower class families and those living in the Southern region of the U.S. Rates increased but later plateaued among African-Americans.