New York, Apr 8 (IANS): Using a bedroom air filter that traps fine particles of pollution with diameters smaller than 2.5 micrometres can significantly improve breathing in asthmatic children, according to a new study.

Fine particulate matter (PM2.5) is a ubiquitous air pollutant originating from fossil fuel emissions, wildfires and other biomass burning, industrial sources, and gasoline- and diesel-powered vehicles.

Thirty times smaller in diameter than a human hair, the particles are easily inhaled and can penetrate deep into the small, or lower, airways where they can trigger or exacerbate asthma symptoms. Inhalers don't help since they are only designed to open upper airways.

The findings, published in the journal JAMA Pediatrics, documented physiological improvements occur in the child's airways when air filters are in use, and it suggests that with consistent use, the filters may help prevent, not just alleviate asthmatic flare-ups.

"Our results show that using an air purifier to reduce the exposure of lower airways to pollutants could help asthmatic children breathe easier without those costly drugs," said study researcher Junfeng Zhang from Duke University in the US.

For the results, the researchers conducted the double-blind crossover study in a Shanghai suburb during a period of moderately high PM2.5 pollution in 2017.

They gave 43 children with mild to moderate asthma two air filters to use in their bedrooms. One was a high-efficiency particulate air (HEPA) filter capable of removing PM2.5; the other was a sham filter.

Each filter was used for two weeks in random order with a two-week interval in between. Neither the children nor their families knew which filter was which.

"Results showed that PM2.5 concentrations inside the children's bedrooms were a third to two-thirds lower when the real air filters were in use than when the sham ones were being used," said researcher Michael H Bergin.

This drop coincided with significant improvements in how easily air flowed in and out of the children's small airways and lungs, Bergin said.

These improvements included a 24 per cent average reduction in total airway resistance, a 43.5 per cent average reduction in small airway resistance, a 73.1 per cent average increase in airway elasticity, and a 27.6 per cent average reduction in exhaled nitric oxide, a biomarker of lung inflammation.

Although the benefits lasted only as long as the real air filters were in use, "it's probable that if children use the filters on an ongoing daily basis they will see continued benefits," Zhang said.