Exposure to traffic-related air pollution and risk of development of childhood asthma: A systematic review and meta-analysis
Top Cited Papers
Open Access
- 1 March 2017
- journal article
- review article
- Published by Elsevier BV in Environment International
- Vol. 100, 1-31
- https://doi.org/10.1016/j.envint.2016.11.012
Abstract
Background and objective: The question of whether children's exposure to traffic-related air pollution (TRAP) contributes to their development of asthma is unresolved. We conducted a systematic review and performed meta analyses to analyze the association between TRAP and asthma development in childhood. Data sources: We systematically reviewed epidemiological studies published until 8 September 2016 and available in the Embase, Ovid MEDLINE (R), and Transport databases. Study eligibility criteria, participants, and interventions: We included studies that examined the association between children's exposure to TRAP metrics and their risk of 'asthma' incidence or lifetime prevalence, from birth to age 18 years old. Study appraisal and synthesis methods: We extracted key characteristics of each included study using a predefined data items template and these were tabulated. We used the Critical Appraisal Skills Programme checklists to assess the validity of each included study. Where four or more independent risk estimates were available for a continuous pollutant exposure, we conducted overall and age-specific meta-analyses, and four sensitivity analyses for each summary meta-analytic exposure-outcome association. Results: Forty-one studies met our eligibility criteria. There was notable variability in asthma definitions, TRAP exposure assessment methods and confounder adjustment. The overall random-effects risk estimates (95% CI) were 1.08 (1.03, 1.14) per 0.5 x 10(-5) m(-1) black carbon (BC), 1.05 (1.02, 1.07) per 4 mu g/m(3) nitrogen dioxide (NO2), 1.48 (0.89, 2.45) per 30 mu g/m(3) nitrogen oxides (NOx), 1.03 (1.01, 1.05) per 1 mu g/m(3) Particulate Matter <2.5 mu m in diameter (PM2.5), and 1.05 (1.02, 1.08) per 2 mu g/m(3) Particulate Matter <10 mu m in diameter (PM10). Sensitivity analyses supported these findings. Across the main analysis and age-specific analysis, the least heterogeneity was seen for the BC estimates, some heterogeneity for the PM2.5 and PM10 estimates and the most heterogeneity for the NO2 and NOx estimates. Limitations, conclusions and implication of key findings: The overall risk estimates from the meta-analyses showed statistically significant associations for BC, NO2, PM2.5, PM10 exposures and risk of asthma development. Our findings support the hypothesis that childhood exposure to TRAP contributes to their development of asthma. Future meta-analyses would benefit from greater standardization of study methods including exposure assessment harmonization, outcome harmonization, confounders' harmonization and the inclusion of all important confounders in individual studies. (C) 2016 Elsevier Ltd. All rights reserved.Keywords
This publication has 105 references indexed in Scilit:
- Asthma incidence in children growing up close to traffic: a registry-based birth cohortEnvironmental Health, 2013
- Measured and modeled personal and environmental NO2 exposurePopulation Health Metrics, 2012
- Urbanisation, asthma and allergiesThorax, 2011
- Traffic density and stationary sources of air pollution associated with wheeze, asthma, and immunoglobulin E from birth to age 5 years among New York City childrenEnvironmental Research, 2011
- Is the prevalence of asthma declining? Systematic review of epidemiological studiesAllergy, 2010
- Does traffic exhaust contribute to the development of asthma and allergic sensitization in children: findings from recent cohort studiesEnvironmental Health, 2009
- Worldwide trends in the prevalence of asthma symptoms: phase III of the International Study of Asthma and Allergies in Childhood (ISAAC)Thorax, 2007
- 50 years of asthma: UK trends from 1955 to 2004Thorax, 2007
- Respiratory health and individual estimated exposure to traffic-related air pollutants in a cohort of young childrenOccupational and Environmental Medicine, 2006
- Measuring inconsistency in meta-analysesBMJ, 2003