Air pollution, bronchiolitis, and asthma: the role of nasal microRNAs

Severe bronchiolitis (ie, bronchiolitis that requires hospitalisation) imposes a substantial acute care burden on infants and leads to chronic respiratory sequelae, such as recurrent wheeze and asthma.1 An increasing number of studies show that, in infants with severe bronchiolitis, environmental exposures play an essential role in the development of asthma. Data from observational studies show that infants with severe bronchiolitis who are exposed to higher levels of air pollution (for example, if their birth residence is located close to a main road) have a 1·2–1·6 times higher risk of developing asthma than those exposed to lower levels of air pollution.