Urban Health – some reflections from Western Australia
by Dr George Crisp.
Perth’s recent rapid growth has resulted in increasing infill and suburban sprawl, which has made the subject of urban planning and its consequences very topical.
DEA was invited to a workshop at the Department of Planning, where a cross section of planners, architects and health professionals discussed issues relating to the urban environment and health. Although the language and approaches were quite different, there was a surprising similarity between the various groups in the desired outcomes, namely; the retention of urban trees, planting of new urban vegetation and increasing green spaces in our city. Expect some commentary on this meeting on the DEA web site shortly.
Over the last few weeks I have also had the opportunity to talk to several groups, including the local councillors and residents, about the relationship between urban design and our health, and have found these groups to be very receptive.
There are numerous factors linking urban design and development with the health of city inhabitants. From a health perspective the main factors include; direct effects and opportunities from natural and green spaces, urban heat islands, air and water pollution and hydrological effects:
- Access to green space has many direct benefits, improving both physical and mental health, especially in children. There are significant differences in health outcomes between suburbs with different proportions of green space, with 25% lower all cause mortality in suburbs with the most versus least green space. Even the view of trees and greenery has been demonstrated to have positive restorative effects, improving recovery times in post-operative patients. Blood pressure falls more when exercise is taken in natural surrounding than other situations. And access to green spaces can promote recreation, social interaction and cohesion, and results in lower local crime rates.
- Replacing natural environments with urban landscapes results in an “Urban Health Island” (UHI) effect. The cooling effects of trees provided by shade and evapotranspiration are lost, but the concrete and bitumen that replaces them absorbs and stores heat, reradiating it at night; tall buildings also compound the retention of heat by trapping reradiated heat. High ambient temperatures already result in significant emergency admissions, mental health impacts and all cause mortality in Australia’s major cities and these effects will be worsened further by climate change but can be ameliorated to some extent by improved urban design, for example tree retention and planting.
- There are clear links between criteria air pollutants (N0x, S02, C0, fine particulate matter and ozone) and human health. Even at very low ambient levels air pollutants can be harmful to our health, some such as fine particulate matter and ozone do not appear to have a lower safe threshold. Green spaces and trees have beneficial effects on local air quality absorbing both the pollutants themselves and can also reducing the secondary aerosols formed by volatile organic compounds (VOCs). Ozone is formed as a secondary product in the atmosphere by the reaction between VOCs and oxides of nitrogen (N0x) in the presence of ultraviolet light and is temperature dependent, increasing urban temperatures therefore increase the ambient levels of ozone and consequent health impacts.
- Rain falling on natural landscapes in primarily absorbed with run off in the order of 5 %, impervious urban surfaces can increase this run off by 400-1000% greatly increasing the likelihood of flooding, which can also lead to a variety of health impacts through loss and displacement or increased risks of water contamination and promoting disease vectors. Heavy precipitation events are also increasing as a result of climate change.
DEA maintains an interest in urban health and encourages members to get involved in the issue in their own area. There are many ways this can be promoted and material you will find helpful is on the DEA web site.
South Australian Public Health Plan South Australia: A Better Place to Live
Submission on “Regulated Trees Amendment”
Inquiry into Environmental Design and Public Health
Healthy Cycling in Amsterdam, Copenhagen and Hobart