The effect of outdoor air pollution on the risk of hospitalisation for bronchiolitis in infants: a systematic review

Charlotte King; Jamie Kirkham; Daniel Hawcutt; Ian Sinha

doi:10.7717/peerj.5352

The effect of outdoor air pollution on the risk of hospitalisation for bronchiolitis in infants: a systematic review

PeerJ. 2018 Aug 28:6:e5352. doi: 10.7717/peerj.5352. eCollection 2018.

Authors

Charlotte King^#¹, Jamie Kirkham², Daniel Hawcutt^#³, Ian Sinha^#⁴

Affiliations

¹ Department of Women and Child's Health, University of Liverpool, Liverpool, UK.
² Department of Biostatistics, University of Liverpool, Liverpool, UK.
³ NIHR Alder Hey Clinical Research Facility, Alder Hey Children's Hospital, Liverpool, UK.
⁴ Department of Respiratory Medicine, Alder Hey Children's Hospital, Liverpool, UK.

^# Contributed equally.

Abstract

Objective: To 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.

Design: Systematic review of observational epidemiological studies including cohort, time series, case crossover and case control study designs.

Data sources: Medline, Scopus, and Web of Science searched to November 2017 with no language restrictions.

Eligibility criteria: Studies 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 measure: Risk of hospitalisation from bronchiolitis.

Results: Eight 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.

Conclusions: Certain 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.

Protocol: The protocol can be found at PROSPERO (CRD42017080643).

Keywords: Air pollution; Bronchiolitis; Hospitalisation; Systematic review.

Grants and funding

Charlotte King is partly funded by the National Institute for Health Research Collaboration for Leadership in Applied Health Research and Care North West Coast (NIHR CLAHRC NWC). There was no additional external funding received for this study. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.