Background There is increasing policy interest in the potential for vegetation in urban areas to mitigate harmful effects of air pollution on respiratory health. We aimed to quantify relationships between tree and green space density and asthma-related hospitalisations, and explore how these varied with exposure to background air pollution concentrations. Methods Population standardised asthma hospitalisation rates (1997–2012) for 26,455 urban residential areas of England were merged with area-level data on vegetation and background air pollutant concentrations. We fitted negative binomial regression models using maximum likelihood estimation to obtain estimates of asthma-vegetation relationships at different levels of pollutant exposure. Results Green space and gardens were associated with reductions in asthma hospitalisation when pollutant exposures were lower but had no significant association when pollutant exposures were higher. In contrast, tree density was associated with reduced asthma hospitalisation when pollutant exposures were higher but had no significant association when pollutant exposures were lower. Conclusions We found differential effects of natural environments at high and low background pollutant concentrations. These findings can provide evidence for urban planning decisions which aim to leverage health co-benefits from environmental improvements.
Bibliographical noteFunding Information:
The authors thank Donna Lynsday at Bluesky International Limited for her expertise on the National Tree Map and for providing access to this dataset for this project. This research was supported by funding provided by a) the National Institute for Health Research Health Protection Research Unit (NIHR HPRU) in Environmental Change and Health at the London School of Hygiene and Tropical Medicine in partnership with Public Health England, and in collaboration with the University of Exeter, University College London, and the Met Office ( HPRU-2012-10016 ); b) UK Medical Research Council (MRC) and UK Natural Environment Research Council (NERC) for the MEDMI Project ( MR/K019341/1 ). The views expressed are those of the authors and not necessarily those of the MRC, NERC, NHS, NIHR, the Department of Health or Public Health England, none of whom were involved in the research design, data analysis or interpretation of findings.
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- Air pollutants
- Ecosystem management
- Green space
- Urban land use