Air pollution increases infants' risk of bronchiolitis

Infants who are exposed to higher levels of air pollution are at increased risk for bronchiolitis, according to a new study.

The study appears in the November 15 issue of the American Thoracic Society's American Journal of Respiratory and Critical Care Medicine.

"There has been very little study of the consequences of early life exposure to air pollution," said Catherine Karr, M.D. PhD, assistant professor of pediatrics at the University of Washington and the paper's lead author. "This study is unique in that we were able to look at multiple sources including wood smoke in a region with relatively low concentrations of ambient air pollution overall."

The researchers analyzed nearly 12,000 diagnoses of infant bronchiolitis between 1999 and 2002 in southwestern British Columbia, with respect to the individual's ambient pollution exposure based on monitored levels of nitric oxide (NO), nitrogen dioxide (NO2), carbon monoxide (CO), sulfur dioxide (SO2), and particulate matter from monitoring stations within 10 km of the infants' homes. They also used land-use regression maps to assess concentrations of ambient pollution with respect to traffic and wood smoke. They analyzed pollution exposure by dividing subjects into four categories, or quartiles, of concentration.

After accounting for confounding variables including sex, gestational age, maternal smoking and breastfeeding, they found that a diagnosis of bronchiolitis was significantly linked to increased lifetime exposure to specific pollutants. An interquartile increase in exposure to NO, NO2, SO2 and CO increased bronchiolitis risk by 8, 12, 4 and 13 percent respectively. Infants who lived within 50 meters of a highway had an increased risk of six percent; those who lived in a higher wood smoke exposure area had an increase of eight percent in their risk of bronchiolitis.