title: Spatial and temporal associations of road traffic noise and air pollution in London: Implications for epidemiological studies.
abstract: Road traffic gives rise to noise and air pollution exposures, both of which are associated with adverse health effects especially for cardiovascular disease, but mechanisms may differ. Understanding the variability in correlations between these pollutants is essential to understand better their separate and joint effects on human health. We explored associations between modelled noise and air pollutants using different spatial units and area characteristics in London in 2003-2010. We modelled annual average exposures to road traffic noise (LAeq,24h, Lden, LAeq,16h, Lnight) for ~190,000 postcode centroids in London using the UK Calculation of Road Traffic Noise (CRTN) method. We used a dispersion model (KCLurban) to model nitrogen dioxide, nitrogen oxide, ozone, total and the traffic-only component of particulate matter ≤2.5μm and ≤10μm. We analysed noise and air pollution correlations at the postcode level (~50 people), postcodes stratified by London Boroughs (~240,000 people), neighbourhoods (Lower layer Super Output Areas) (~1600 people), 1km grid squares, air pollution tertiles, 50m, 100m and 200m in distance from major roads and by deprivation tertiles. Across all London postcodes, we observed overall moderate correlations between modelled noise and air pollution that were stable over time (Spearman's rho range: |0.34-0.55|). Correlations, however, varied considerably depending on the spatial unit: largest ranges were seen in neighbourhoods and 1km grid squares (both Spearman's rho range: |0.01-0.87|) and was less for Boroughs (Spearman's rho range: |0.21-0.78|). There was little difference in correlations between exposure tertiles, distance from road or deprivation tertiles. Associations between noise and air pollution at the relevant geographical unit of analysis need to be carefully considered in any epidemiological analysis, in particular in complex urban areas. Low correlations near roads, however, suggest that independent effects of road noise and traffic-related air pollution can be reliably determined within London.
authors.affiliation: UK Small Area Health Statistics Unit, MRC-PHE Centre for Environment and Health, Imperial College London, St Mary's Campus, Norfolk Place, London W2 1PG, UK. Electronic address: d.fecht@imperial.ac.uk.
authors.forename: Daniela
authors.initials: D
authors.lastname: Fecht
authors.affiliation: UK Small Area Health Statistics Unit, MRC-PHE Centre for Environment and Health, Imperial College London, St Mary's Campus, Norfolk Place, London W2 1PG, UK; Imperial College Healthcare NHS Trust, London, UK.
authors.forename: Anna L
authors.initials: AL
authors.lastname: Hansell
authors.affiliation: UK Small Area Health Statistics Unit, MRC-PHE Centre for Environment and Health, Imperial College London, St Mary's Campus, Norfolk Place, London W2 1PG, UK.
authors.forename: David
authors.initials: D
authors.lastname: Morley
authors.affiliation: Environmental Research Group, MRC-PHE Centre for Environment and Health, King's College London, 150 Stamford Street, London SE1 9NH, UK.
authors.forename: David
authors.initials: D
authors.lastname: Dajnak
authors.affiliation: UK Small Area Health Statistics Unit, MRC-PHE Centre for Environment and Health, Imperial College London, St Mary's Campus, Norfolk Place, London W2 1PG, UK.
authors.forename: Danielle
authors.initials: D
authors.lastname: Vienneau
authors.affiliation: Environmental Research Group, MRC-PHE Centre for Environment and Health, King's College London, 150 Stamford Street, London SE1 9NH, UK.
authors.forename: Sean
authors.initials: S
authors.lastname: Beevers
authors.affiliation: UK Small Area Health Statistics Unit, MRC-PHE Centre for Environment and Health, Imperial College London, St Mary's Campus, Norfolk Place, London W2 1PG, UK.
authors.forename: Mireille B
authors.initials: MB
authors.lastname: Toledano
authors.affiliation: Environmental Research Group, MRC-PHE Centre for Environment and Health, King's College London, 150 Stamford Street, London SE1 9NH, UK.
authors.forename: Frank J
authors.initials: FJ
authors.lastname: Kelly
authors.affiliation: Environmental Research Group, MRC-PHE Centre for Environment and Health, King's College London, 150 Stamford Street, London SE1 9NH, UK; St George's, University of London, Cranmer Terrace, London SW17 0RE, UK.
authors.forename: H Ross
authors.initials: HR
authors.lastname: Anderson
authors.affiliation: UK Small Area Health Statistics Unit, MRC-PHE Centre for Environment and Health, Imperial College London, St Mary's Campus, Norfolk Place, London W2 1PG, UK.
authors.forename: John
authors.initials: J
authors.lastname: Gulliver
mesh_terms: D000393:Air Pollutants / Q000032:analysis*; D000397:Air Pollution / Q000032:analysis*; D016021:Epidemiologic Studies; D005843:Geography; D006801:Humans; D008131:London; D008962:Models, Theoretical; D009622:Noise
chemical_list: D000393:Air Pollutants
keywords: Air pollution; Correlation; Exposure assessment; London; Noise; Road traffic