Air pollution is a global issue and a significant contributor to preventable illness and early death. In 2012, the World Health Organisation (WHO) reported that air pollution is responsible for approximately one in nine deaths every year. In this article, Senior Urban Designer and Associate, Rebecca Frost, discusses how architects and urban designers have a crucial role in mitigating primary pollutants by designing more sustainable and healthy places.
JTP project, Radio Station Rugby, utilises large green and blue corridors which play an important role as carbon sinks. © Urban&Civic
Research shows that exposure to pollutants can stunt brain and lung growth in children, exacerbate respiratory illnesses such as asthma, and cause earlier onset of dementia among older people. UNICEF has shown that one in three children are growing up in UK cities with unsafe levels of particulate pollution. In a recent landmark case, a coroner ruled that air pollution made a material contribution to the death of nine year old Ella Kissi-Debrah; the first time in the UK that air pollution has been listed as the cause of death. It was reported that exposure to nitrogen oxide and particulate matter (PM2.5) contributed to her death, which were at levels in excess of the WHO’s guidelines.
While some progress has been made, with emissions of nitrogen oxides falling by 33% between 2010 and 2018, further innovative approaches are required, at national and local level, to tackle the single greatest environmental risk to human health. At a national level, the British government set out the Clean Air Strategy in January 2019, followed by the Environmental Bill, which delivers key aspects of this strategy including legally binding targets to reduce emissions from the five primary pollutants by 2020 and 2030. However, it was reported at the end of 2019 that the UK was falling short of two of the five targets.
Air pollution comes from a wide range of sources, but the main contributors are industry, vehicles, cooking and heating. Fine Particulate Matter (PM2.5) is the biggest threat to human health. There are three things we, as placemakers and built environment practitioners, can do to design for better air quality.
Promote active forms of travel
Designing walkable neighbourhoods gives residents the opportunity to choose a more sustainable and active form of travel and limits the use of vehicles, which are a key contributor to air pollutants. A study of exposure to pollutants while commuting in Sheffield showed that while all participants experienced levels over the WHO recommended safe limit, cycling had the lowest exposure compared to walking and travelling by car, with the car having the highest PM2.5 levels. Research has also shown that an optimal walking commute is 15 minutes – anything more than this and people are less likely to do it, especially in winter months. We therefore need to design new neighbourhoods with the 15-minute city design principles in mind.
- Give residents an option to not use the car by making the active travel route more appealing through incorporating green space and segregating cycle lanes away from traffic to reduce exposure.
- Promote mixed use development, providing local shopping, play, leisure and meeting places, and reducing the need to travel. Furthermore, enable commuters to make an informed decision about where and how to travel. For example, local authorities are creating ‘air maps’ to inform the local community where higher concentrations of pollutants are present.
- Promote and encourage low emission vehicles.
- Introduce low emissions zones to encourage operators to choose alternative fuel sources and improve the energy performance of vehicles.
- Reconsider the patterns of travellers from home to a place of work – the Covid-19 lockdown has required employees to work from home, thereby removing the requirement to commute to work. While permanent home working is not sustainable in the long-term for many, it does demonstrate that it is possible for us to reconsider the ‘workplace’. We can design communal workspaces within neighbourhoods in which we live with desks to rent – providing the opportunity to choose not to commute every day.
JTP promotes a landscape-led masterplanning approach on projects to bring biodiversity net gains to neighbourhoods and create natural landscapes and parks that capture carbon at a strategic level.
Allow places to ‘breathe’
Air pollution issues are compounded in cities due to poor design. The below map illustrates PM2.5 concentrations are higher in cities across the UK. Densely clustered, tall buildings create Urban Heat Islands (UHI) and urban canyons, causing elevated emissions of air pollutants and greenhouse gases.
- Encourage the use of living walls and/or green roofs to reduce the number of reflective surfaces contributing to the UHI and to increase the evapotranspiration and provide cooling.
- Vary and lower building heights to enable winds to flow through streets and spaces, allowing for cooling and letting particulate matter dissipate.
- Consider alternative surface materials – dark tarmac absorbs more solar radiation, exacerbating the UHI effect.
Map illustrating PM2.5 concentrations, which are higher in cities across the UK. © Crown copyright
Use trees, but in the right places
JTP promotes a landscape-led masterplanning approach and has been collaborating with The Wildlife Trust on several projects to bring biodiversity net gains to neighbourhoods and create natural landscapes and parks that people love. Leading with the landscape has the added benefit of capturing carbon at a strategic level as well as reducing the carbon footprint within the home.
During the recent lockdowns in the UK, people have reported spending more time in nature. We are instinctively drawn to see natural sights. Bringing nature back into our cities will not only improve health and wellbeing (studies show that being in nature, or exposure to it contributes to physical wellbeing, reducing blood pressure, heart rate, muscle tension and the production of stress hormones), it has also been shown that the correct placement of plants at street level can reduce the concentration of the harmful nitrogen dioxide by 40% and microscopic particulate matter (PM2.5) by 60%. Furthermore, studies have shown that the presence of water bodies can prevent long-term accumulation of pollutants in surrounding areas.
Trees play an important role as carbon sinks, absorbing up to 48 pounds of carbon dioxide per tree, per year. They also absorb pollutants and toxins.
- Adopt a landscape-led masterplanning approach, ensuring nature is integral to the place.
- Introduce street trees, ensuring they are the correct species, suited to their location and therefore require little management. Species should also be selected if they are disease resistant and long-living.
- Manage the use of water in our streets through swales and urban channels.
- Create a continuous network of trees and green spaces rather than fragmented pockets – ensuring a space for wildlife and people to use.
Air pollution is estimated to cost the UK economy billions of pounds each year. By introducing more vegetation, making walking and cycling the easier and preferred modes of transport and providing opportunities for more sustainable forms of energy production, we will create more healthy and sustainable places whilst also improving wellbeing.