Bronchiolitis poses significant public health burden.

Bronchiolitis is the leading cause of infant morbidity, and hospitalization rates are rising. The effect of this disease is not limited to the acute illness episode. Approximately 40% to 50% of children diagnosed with bronchiolitis suffer from subsequent wheezing and airway reactivity or asthma. Attempts to address the burden of this disease via vaccine development have been largely unsuccessful, and treatment is purely supportive rather than curative. As such, primary prevention is paramount. If outdoor air pollution exacerbates this disease, as has been found for other pediatric respiratory diseases, actions to ensure that regulatory standards protect this vulnerable population will be paramount. Increased anatomic and physiologic susceptibility to the pro-inflammatory effects of air pollutants, coupled with the pro-inflammatory response in bronchiolitis, underlies the concern that infants exposed to higher levels of ambient air pollutants may be at increased risk for developing more severe bronchiolitis requiring hospitalization.