Abstract
ObjectiveTo systematically review the evidence around the effect of ambient levels of particulate and gaseous pollutants, and the risk of hospitalisation with bronchiolitis for infants under two years of age.DesignSystematic review of observational epidemiological studies including cohort, time series, case crossover and case control study designs.Data sourcesMedline, Scopus, and Web of Science searched to November 2017 with no language restrictions.Eligibility criteriaStudies investigating impact of air pollution levels on particulate pollutants (diameter <2.5 μm (PM2.5) or <10 μm (PM10) and gaseous pollutants (nitrogen dioxide (NO2), sulphur dioxide (SO2), carbon monoxide (CO), ozone (O3)) on hospital admission for bronchiolitis.Main outcome measureRisk of hospitalisation from bronchiolitis.ResultsEight studies were eligible for review. Long term exposure to PM2.5 may be associated with increased risk of hospitalisation for bronchiolitis. SO2 may also be associated with hospitalisation, but results for other pollutants are inconsistent between studies. In three of the five studies that showed a positive association between air pollutants and hospitalisation, measured concentrations were below World Health Organization (WHO) recommended levels.ConclusionsCertain particulate and gaseous pollutants may have a clinically relevant effect on hospital admissions for bronchiolitis in children below age two years old. Large cohort or time series studies are needed to examine this possible association.ProtocolThe protocol can be found at PROSPERO (CRD42017080643).
Highlights
Bronchiolitis is a common lower respiratory infection in infancy, it is caused by respiratory syncytial virus (RSV) in 80% of cases (Jhawar, 2003)
Inclusion criteria and study selection We included cohort, time series, case crossovers or case control study designs (based on previous methodology by Shah et al (2015)) that evaluated the impact of air pollution levels (PM2.5, Particulate matter diameter
Six of the studies were from overlapping research groups in North America (Girguis et al, 2017; Karr et al, 2004, 2006, 2007, 2009a, 2009b), one from France (Segala et al, 2008) and one from Malaysia (Abdul Rahman et al, 2017) a developing country
Summary
Bronchiolitis is a common lower respiratory infection in infancy, it is caused by respiratory syncytial virus (RSV) in 80% of cases (Jhawar, 2003). RSV, spread by droplet transmission (Leung, Kellner & Davies, 2005), causes airway inflammation (Nicolai et al, 2013), bronchial epithelial cell necrosis (Leung, Kellner & Davies, 2005), and other pathogenic. How to cite this article King et al (2018), The effect of outdoor air pollution on the risk of hospitalisation for bronchiolitis in infants: a systematic review. Mechanical processes such as construction activities, road dust re-suspension and wind
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