Plants protecting people from pollution

Plants play an important role in our lives, but of all the benefits they bring, the potential to help mitigate air pollution is often overlooked. Globally, exposure to air pollution is estimated to cause 7 million premature deaths annually, with reduced lung growth and aggravated asthma in children, alongside heart disease and stroke in adults, attributed to outdoor air pollution. In the UK, poor outdoor air quality is linked to 40,000 deaths each year.

Using plants - otherwise known as green infrastructure (GI) - to help mitigate air pollution is a concept promoted within the National Planning Policy Framework (NPPF), by the Mayor of London, and by a number of planning authorities across the UK and beyond. The latest version of the NPPF states the following: “Opportunities to improve air quality or mitigate impacts should be identified, such as through … green infrastructure provision and enhancement.”

GI can play an important role in removing air pollutants through deposition to leaf surfaces on a national scale, and the careful positioning of tree-lines and hedgerows alongside busy roads can reduce human exposure to pollution from vehicle exhausts at the local scale. Certain species of tree (e.g. Yew) have even been shown to have a very high capacity to capture ultra-fine particulate matter.

An example of how GI has been implemented into the design of a development is the University of York’s living wall. Although research has shown that care must be taken when considering the use of living walls, the ability to offer natural ventilation and assist with air purification was cited as one of its many benefits. On a larger scale, the city of Barcelona has a strong commitment to GI, linking GI to a range of benefits including improved air quality, improved biodiversity and reduced noise pollution.

With the World Health Organisation recently reducing their recommended limits on key atmospheric pollutants, the use of plants to help mitigate air pollution is of growing interest globally. Very recent developments have been made in quantifying site-specific air quality impacts of roadside vegetation barriers. The Green Infrastructure for Roadside Air Quality (GI4RAQ) platform is a protype developing software with the aim of enabling urban practitioners to estimate the site-specific air quality impacts of street planting at the planning stage.

The Air Quality team at SLR is looking at how we can help our clients use plants to help mitigate air pollution. Please get in touch to discuss your ongoing and upcoming projects, and see how we can help. 

This article was written by Steven Lees - Air Quality Consultant

References:

• World Health Organisation. New WHO Global Air Quality Guidelines aim to save millions of lives from air pollution. News Release (2021).
• Toxic air in the UK requires immediate action - The Lancet Planetary Health, accessed: October 2021.
• Mayor of London. Using Green Infrastructure to Protect People from Air Pollution (2019).
• Wang, H. et al. Efficient Removal of Ultrafine Particles from Diesel Exhaust by Selected Tree Species: Implications for Roadside Planting for Improving the Quality of Urban Air. Environ. Sci. Technol (2019). 
• Green walls: a red card for office worker health? - News and events, University of York, accessed: October 2021.
• University of York (ansgroupglobal.com), accessed: October 2021.
• Ajuntament de Barcelona. Barcelona Green Infrastructure and Biodiversity Plan 2020 (2013).
• Pearce, H. et al. Introducing the Green Infrastructure for Roadside Air Quality (GI4RAQ) Platform: Estimating Site-Specific Changes in the Dispersion of Vehicular Pollution Close to Source. Forests (2021).