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Icth2015 hk monday_6_jul

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Exposure to traffic related air pollution and the onset of childhood asthma: is there a connection?

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Icth2015 hk monday_6_jul

  1. 1. Session: New perspectives on vulnerable groups Does traffic-related air pollution cause childhood asthma? Haneen Khreis1, Charlotte Kelly1,2, James Tate1, Roger Parslow3 and Karen Lucas1 1 Institute for Transport Studies, 2 Leeds Institute of Health Sciences, 3 Leeds Institute of Cardiovascular and Metabolic Medicine, University of Leeds Changing Perspectives: 1st International Conference on Transport and Health, London, 6 – 8 July 2015
  2. 2. 50 years of asthma: UK trends from 1955 to 2004 Trends in the prevalence of a diagnosis of asthma ever in children. m, month; y, year. Source: Anderson et al. (2007)
  3. 3. Why such steady and rapid increases? “… the increase in disease must be attributable to a change in as-yet unknown environmental factors… ” (Cookson, 2004, p. 979) Source: Brook (2012)
  4. 4. Does children’s exposure to traffic- related air pollution increase their risks of developing asthma? Meta-analysis Case study - The Born in Bradford Systematic review Provide data Learn and apply lessons
  5. 5. Does children’s exposure to traffic-related air pollution increase their risks of developing asthma? 3. Include studies which investigate children’s exposure to traffic-related air pollution only1. Include human studies only 2. and children’s studies only 4. Include studies which investigate exposure to traffic-related air pollution or traffic-related air pollutants when road traffic is specified as their source 6. Include studies which specifically investigate the subsequent risk of asthma development in childhood 7. Include observational studies only 5. Include studies which report measures of association and their confidence interval precision Khreis et al. (2014). Exposure to traffic-related air pollution and the development of childhood asthma. PROSPERO 2014:CRD42014015448, available from: http://www.crd.york.ac.uk/PROSPERO/display_record.asp?ID=CRD42014015448
  6. 6. Screening process
  7. 7. Research gaps and impact on validity: asthma definitions • Heterogeneous disease • No universally accepted definition • Has many phenotypes • AND non-specific symptoms….
  8. 8. Research gaps and impact on validity: asthma definitions Self-report of doctor-diagnosis = 12.0% Hospitalization registry = 6.6% Prescription registry = 32.2% Source: Hansen et al. (2012)
  9. 9. Research gaps and impact on validity: asthma definitions Self-report of doctor-diagnosis = 12.0% Hospitalization registry = 6.6% Prescription registry = 32.2% 1 12 Source: Hansen et al. (2012)
  10. 10. Research gaps and impact on validity: exposure models 0 50000 100000 150000 200000 250000 300000 16:38:32 16:39:27 16:40:22 16:41:17 16:42:12 16:43:07 16:44:02 16:44:57 16:45:52 16:46:47 16:47:42 16:48:37 16:49:32 16:50:27 16:51:22 16:52:17 16:53:12 16:54:07 16:55:02 16:55:57 16:56:52 16:57:47 16:58:42 16:59:37 17:00:32 17:01:27 17:02:22 17:03:17 17:04:12 17:05:07 17:06:02 17:06:57 17:07:52 17:08:47 17:09:42 17:10:37 17:11:32 17:12:27 17:13:22 17:14:17 17:15:12 17:16:07 17:17:02 17:17:57 17:18:52 17:19:47 17:20:42 Background Site Background Site Intersection Corner Bus Stop Road Crossing Bus Stop Intersection Corner Road Crossing Intersection Corner Intersection Corner Road Crossing Fay D, Tate J, Khreis H (2015): Investigating pedestrians PNC exposures in urban micro-environments near a busy road traffic intersection
  11. 11. Research gaps and impact on validity: exposure models 0 50000 100000 150000 200000 250000 300000 16:38:32 16:39:27 16:40:22 16:41:17 16:42:12 16:43:07 16:44:02 16:44:57 16:45:52 16:46:47 16:47:42 16:48:37 16:49:32 16:50:27 16:51:22 16:52:17 16:53:12 16:54:07 16:55:02 16:55:57 16:56:52 16:57:47 16:58:42 16:59:37 17:00:32 17:01:27 17:02:22 17:03:17 17:04:12 17:05:07 17:06:02 17:06:57 17:07:52 17:08:47 17:09:42 17:10:37 17:11:32 17:12:27 17:13:22 17:14:17 17:15:12 17:16:07 17:17:02 17:17:57 17:18:52 17:19:47 17:20:42 Background Site Background Site Intersection Corner Bus Stop Road Crossing Bus Stop Intersection Corner Road Crossing Intersection Corner Intersection Corner Road Crossing Fay D, Tate J, Khreis H (2015): Investigating pedestrians PNC exposures in urban micro-environments near a busy road traffic intersection
  12. 12. Research gaps and impact on validity: exposure models Proximity to roadways Regulatory monitoring stations Land-use regression models Dispersion models
  13. 13. Research gaps and impact on validity: exposure models 10 studies reporting 30 risk estimates, 53% were positive (31% significant) 4 studies reporting 28 risk estimates, 93% were positive (65% significant) 10 studies reporting 55 risk estimates, 93% were positive (29% significant) 4 studies reporting 40 risk estimates, 50% were positive (35% significant)
  14. 14. 23 studies, 153 main risk estimates from 4 exposure models, 114 (75%) positive, 45 (39%) statistically significant… and more from the other exposure models… 3 5 1 1 3 3 1 2 3 1
  15. 15. So does traffic-related air pollution cause asthma? “The results found across the studies followed a pattern that would be expected under the plausible assumption that the pollutants really are causally associated with asthma development, if only among a subset of children…” (HEI, 2010, p.363)
  16. 16. But… Which pollutant(s)…
  17. 17. But… … and why this heterogeneity? • Differences in study designs, populations, exposure models, outcome definitions and confounders selection • Certain susceptibility factors may be one reason (early life exposures, sex) • Only certain phenotypes of asthma may be affected?
  18. 18. • Traffic-related air pollution might have contributed to the recent asthma epidemic • Effect estimates are very likely to have been distorted/ underestimated • Many effects were detected in areas meeting the relevant air quality guidelines • Black Carbon (and ultra-fine particles) are yet unregulated Implications
  19. 19. • Traffic-related air pollution is a modifiable environmental factor • Black Carbon (and ultra-fine particles) are truly traffic-related pollutants • -28% / -40% decreases in Black Carbon in the Milan congestion charging area (Mattioli, 2014) • A substantial proportion of asthma cases can be prevented? Implications
  20. 20. Thank you!
  21. 21. References • Anderson, H. R., Gupta, R., Strachan, D. P., & Limb, E. S. (2007). 50 years of asthma: UK trends from 1955 to 2004. Thorax, 62(1), 85-90. • Brook, J. R. (2012) 'Estimating exposure to traffic-related air pollution', in Health Effects Institute Annual Conference, Chicago, Illinois, 15-17th April 2012. • Cookson, W. (2004). The immunogenetics of asthma and eczema: a new focus on the epithelium. Nature Reviews Immunology, 4(12), 978-988. • Hansen, S., Strom, M., Maslova, E., Mortensen, E. L., Granstrom, C., & Olsen, S. F. (2012). A comparison of three methods to measure asthma in epidemiologic studies: results from the Danish National Birth Cohort. PloS one, 7(5), e36328. • Health Effects Institute, H. E. I. (2010) Traffic-related air pollution: a critical review of the literature on emissions, exposure, and health effects, Health Effects Institute. • Khreis H, Kelly C, Tate J, Parslow R (2014). Exposure to traffic-related air pollution and the development of childhood asthma. PROSPERO :CRD42014015448, available from: http://www.crd.york.ac.uk/PROSPERO/display_record.asp?ID=CRD42014015448 • Mattioli, G. (2015). Pollution or congestion charging? Air quality measures and road pricing in Milan, Italy, in Institute for Transport Studies Research Seminar Series, University of Leeds, 05 March 2015.

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