With house building a priority for the new UK Government, University of Bath engineers have co-authored research that urges city planners not to forget to build parks and to include green spaces in new communities.

Researchers in the Faculty of Engineering & Design worked with partners led by the University of Surrey's Global Centre for Clean Air Research (GCARE) on a new study that found parks are the most effective green, blue and grey infrastructure (GBGI) at reducing air pollution city-wide by up to 22%.

When the study looked at the air pollution reduction capabilities of 51 different types of GBGI, such as trees, green walls, hedges and parks, it found a mixed bag. Open-road conditions were the most effective context for planting trees, reducing air pollution by up to 77%. However, the research team did find that planting trees in a street canyon can sometimes worsen air quality because of the lack of ventilation that some tree species and configurations exacerbate.

The research is part of the RECLAIM (Reclaiming Forgotten Cities - Turning Cities from Vulnerable Spaces to Healthy Places for People) project. RECLAIM is a £1.45m UK Research and Innovation-funded Network+ initiative. It is led by GCARE in collaboration with Bath, as well as the UK Centre for Ecology & Hydrology and the Universities of Bangor and Warwick.

Professor Prashant Kumar, lead author of the study and Founding Director of GCARE at the University of Surrey, and the Director of the RECLAIM, said: "We are beginning to understand just how powerful green infrastructure can be against urban air pollution, but their effectiveness hinges on where and how they are implemented. Our review has found that well-placed greenery can cut black carbon levels by up to 40%, making our communities greener and healthier."

Dr Jannis Wenk, a Senior Lecturer in Bath’s Department of Chemical Engineering, and co-author of the study, said: "Urban environments, particularly streets, are at the forefront of climate change impacts and require effective pollution mitigation strategies across the UK.

“Our role in field monitoring of green-blue infrastructure solutions, developing case studies, and integrating models for regional upscaling will help create more resilient, sustainable urban spaces that address immediate environmental concerns and benefit generations to come."

Dr Thomas Kjeldsen from the Department of Architecture and Civil Engineering also contributed to the study.

According to the World Health Organization, ambient (outdoor) air pollution caused 4.2 million deaths in 2019. Major sources of outdoor air pollution include vehicles, power generation, and residential energy for cooking and heating.

The researchers reviewed hundreds of studies, analysing the effectiveness of various GBGIs, such as street trees and green roofs, in cutting down pollutants linked to these premature deaths.

Professor Kumar added: "We have discovered that many of the GBGI lack scientific evidence regarding their effectiveness in removing air pollution. Decisions are often based on expert judgments, and so it is crucial that we fill this knowledge gap as quickly as possible for informed decision-making and maximising the potential of GBGI."

The study, Air Pollution Abatement from Green-Blue-Grey Infrastructure, has been published in the journal The Innovation Geoscience (DOI: 10.59717/j.xinn-geo.2024.100100)