Outdoor Air Pollution and Asthma in Children

Background. Asthma, a chronic inflammatory disease of the airways, is associated with reversible airway obstruction and hyperresponsiveness to triggers; clinical symptoms include wheezing, episodic cough, shortness of breath, and increased mucous production. Ambient or outdoor environmental exposure to ozone, particulate matter, sulfur dioxide, and nitrogen oxides has been well documented to exacerbate asthma. Children appear to be most vulnerable to the harmful effects of ambient air pollutants. As their lungs are not completely developed, children may experience greater exposure to environmental pollutants than adults and the higher doses of varied composition may remain in their lungs for a greater duration. Altogether, the negative effects of air pollutants on pulmonary function place children at a greater risk of air pollutant-induced exacerbation of asthma for the duration of their lives. Objectives. The aim of this review was to assess recently published literature regarding the influence of air pollution on asthma in children. Methods. For this work, we reviewed articles found in PubMed using the key words "outdoor air pollution, asthma, and children" which were published between 2006 and 2009. Only those articles that had a full version available in PubMed were analyzed. Results. We reviewed studies published between 2006 and 2009 examining the effect of outdoor air pollution on asthma in children. In total, we evaluated 25 articles; of these, 9 were published in 2006, 3 in 2007, 8 in 2008, and 5 in 2009. Of these 25 studies, 1 was a clinical trial, 6 were cross-sectional, 4 were case-control (2 with a case-crossover design), 12 were cohort prospective, and 2 were cohort retrospective studies with varied follow-up times ranging from 10 days to 7 years. The ages of children also differed, ranging from birth to 18 years of age. Conclusions. All studies reviewed in this work indicate that outdoor air pollution affects the appearance and exacerbation of asthma in children. Although these findings are of great interest, the limitations of noted works make future investigations of the effect of air pollution on asthma in children essential.