A fall in air pollution rapidly reduces inflammation in the airways of children with asthma and improves their lung function, researchers report in the journal Pediatrics this month.

After the 37 children in the study moved from an urban to a rural environment, levels of inflammatory cells called eosinophils in the nose dropped fourfold and a significant reduction in levels of nitric oxide in exhaled breath was seen. Exhaled nitric oxide is thought to reflect the degree of inflammation in the airways.

"This study provides the first objective evidence that limiting real-life exposure of allergic asthmatic children to outdoor air pollution is followed by measurable reduction in airway inflammation and improved airway function, implying that better air quality may rapidly lead to clinical improvement," Dr. Giovanni Piedimonte of the West Virginia University, in Morgantown, and co-researchers state.

All of the children in the study had mild persistent asthma and lived in a highly polluted city before moving to a less polluted rural environment. At both locales, air pollution, pollen counts, and meteorological conditions were monitored.

Relocation to a less polluted environment was also associated with an improvement in lower airway function, as indicated by a marked increase in the amount of air they could expel.

The findings suggest that "lowering the exposure of allergic asthmatic children to airborne pollutants is rapidly followed by measurable improvements in airway inflammation and function," Piedimonte and colleagues conclude.