MedWire News: Inner-city children with asthma face an increased risk of respiratory problems if they are exposed to short-term increases in air pollution from traffic, study results show.

Furthermore, this increased risk occurred at pollution levels deemed 'safe' under US National Ambient Air Quality Standards.

Dr George O'Connor, from Boston University School of Medicine in Massachusetts, USA, and colleagues studied the relationship between pollution levels and respiratory health among 861 children with asthma, aged an average of 8 years, from seven US inner-city communities.

All the participants underwent regular lung function tests over the course of the 2-year study. The results of these tests were compared with local pollution measurements taken up to 5 days previously.

The researchers found that increases in 5-day average concentrations of nitrogen dioxide, sulphur dioxide and pollutant particles smaller than 2.5 µm were significantly associated with reduced lung function among the children.

Furthermore, higher concentrations of nitrogen dioxide and pollutant particles smaller than 2.5 µm were associated with more missed school days and an increased risk of asthma symptoms.

Dr O'Connor and team summarise: "We observed significant associations between pollutant exposures and respiratory health outcomes in a large sample of children with asthma in seven urban US communities, despite the fact that the daily pollutant concentrations were almost all below the current National Ambient Air Quality Standards."

They conclude: "Given the high prevalence of asthma in urban communities, these findings have important implications for air quality regulation and urban transportation policy."

The research is published in the Journal of Allergy and Clinical Immunology.