title: London Hybrid Exposure Model: Improving Human Exposure Estimates to NO2and PM2.5in an Urban Setting.
abstract: Here we describe the development of the London Hybrid Exposure Model (LHEM), which calculates exposure of the Greater London population to outdoor air pollution sources, in-buildings, in-vehicles, and outdoors, using survey data of when and where people spend their time. For comparison and to estimate exposure misclassification we compared Londoners LHEM exposure with exposure at the residential address, a commonly used exposure metric in epidemiological research. In 2011, the mean annual LHEM exposure to outdoor sources was estimated to be 37% lower for PM2.5and 63% lower for NO2than at the residential address. These decreased estimates reflect the effects of reduced exposure indoors, the amount of time spent indoors (∼95%), and the mode and duration of travel in London. We find that an individual's exposure to PM2.5and NO2outside their residential address is highly correlated (Pearson's R of 0.9). In contrast, LHEM exposure estimates for PM2.5and NO2suggest that the degree of correlation is influenced by their exposure in different transport modes. Further development of the LHEM has the potential to increase the understanding of exposure error and bias in time-series and cohort studies and thus better distinguish the independent effects of NO2and PM2.5.
authors.forename: James David
authors.initials: JD
authors.lastname: Smith
authors.forename: Christina
authors.initials: C
authors.lastname: Mitsakou
authors.forename: Nutthida
authors.initials: N
authors.lastname: Kitwiroon
authors.forename: Ben M
authors.initials: BM
authors.lastname: Barratt
authors.forename: Heather A
authors.initials: HA
authors.lastname: Walton
authors.affiliation: UCL Institute for Environmental Design and Engineering, University College London , London, U.K. WC1E 6BT.
authors.forename: Jonathon G
authors.initials: JG
authors.lastname: Taylor
authors.forename: Hugh Ross
authors.initials: HR
authors.lastname: Anderson
authors.forename: Frank J
authors.initials: FJ
authors.lastname: Kelly
authors.forename: Sean D
authors.initials: SD
authors.lastname: Beevers
mesh_terms: D000393:Air Pollutants; D000397:Air Pollution; D006801:Humans; D008131:London; D008962:Models, Theoretical; D052638:Particulate Matter
chemical_list: D000393:Air Pollutants; D052638:Particulate Matter