Clean Air Day 2019: Can Vegetation Protect us from Air Pollution?

On Clean Air Day, our air quality team asks: can vegetation protect us from air pollution?

The use of green infrastructure (e.g. hedgerows and tree-lines) to combat air pollution is a topical point of discussion amongst air quality professionals. With elevated levels of air pollutants such as nitrogen dioxide and fine particulate matter (<10µm in diameter) being increasingly linked to detrimental effects on human health, the need to tackle poor air quality, particularly in urban areas, is a rising priority.

The Mayor of London has recently published a guidance document discussing the use of green infrastructure to protect people from air pollution[1]. The guidance indicates that at the national and regional scale, vegetation plays an important role in removing air pollutants through deposition to leaf surfaces.

However, at the street scale the guidance suggests that the main value of green infrastructure is the role it can play in adjusting the distribution of pollution to reduce human exposure. Therefore, vegetation needs to be planted in the right place to have the intended beneficial effects. In the wrong position, vegetation can actually exacerbate poor air quality conditions.

Contemporary research undertaken by a team of research scientists[2], comprising researchers from China and the U.K., indicates that trees such as yew, sliver birch and elder have very high capabilities for capture of airborne ultra-fine particulate matter (<1µm in diameter). The potential for targeted roadside planting of these species within urban areas, to reduce human exposure to ultra-fine particulate matter, certainly warrants further attention.

The role green infrastructure can play in mitigating air pollution is still subject to ongoing study, however it’s application clearly offers potential in the right situations. Here at Wardell Armstrong our air quality team are currently working alongside our landscape architects to determine the potential for green infrastructure as a mitigation option for air quality.

The air quality team, which comprises specialists situated across the UK, have expertise in undertaking air quality, dust and odour assessments for planning and permitting applications. Should you have a project for which you think we can help, please get in touch!

[1] www.london.gov.uk/sites/default/files/green_infrastruture_air_pollution_may_19.pdf

[2] Wang, H., Maher, B.A., Ahmed, I.A.M., Davison, B. 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)