Scientists reveal blind spot over gardens and air pollution

A new review led by the University of East London (UEL) has uncovered a major blind spot in air pollution research. Despite domestic gardens covering vast areas of Britain's towns and cities, researchers found no direct  evidence showing whether they reduce pollution levels or improve the air people breathe at home. There is a huge gap about the role of domestic gardens on air quality.

Published in the per-reviewed Nature-Based Solutions, the research examined more than 34,000 studies. Just 43 met the criteria for investigating gardens and air pollution, and none directly measured whether domestic gardens reduced pollutant concentrations or improved household air quality.

The finding is significant given the scale of domestic green space. In the UK alone, an estimated 25.8 million gardens cover around 959,800 hectares, while domestic gardens account for approximately 41 per cent of London's total area.

Evidence from larger green spaces may not apply to gardens

The review found strong evidence from wider green infrastructure research that trees, hedges, shrubs, green walls and other vegetation can capture particulate matter on their surfaces and absorb gaseous pollutants.

However, the authors warn that these findings cannot simply be applied to domestic gardens, where buildings, fences, sheds, parked cars and mixed planting create very different patterns of airflow and pollutant movement.

Dense vegetation, for example, may trap pollution on leaf surfaces but can also reduce ventilation, potentially allowing polluted air to build up. Hedges may shield parts of a garden from traffic emissions, but their effectiveness depends on factors including their height, density, distance from roads, surrounding buildings and weather conditions.

Lead author Dr Karina Corada-Pérez, Research Fellow in Air Quality and Green Infrastructure at UEL’s Sustainability Research Institute, said,

Most of us think of gardens as healthy green spaces, and they absolutely provide many important benefits. But when it comes to air quality, we simply don't yet know enough.

Plants can capture pollutants, but a garden is much more than a collection of individual plants. Its layout, boundaries, proximity to roads and buildings, and the way air moves through the space may all influence whether vegetation helps reduce pollution or allows it to accumulate.

Because millions of people spend time in their gardens, grow food in them and open their homes onto them, we urgently need research in real domestic gardens. Only then can we give homeowners, planners and policymakers reliable advice about which planting choices are most likely to support cleaner air."

Questions for people growing food near busy roads

The review also raises important questions for people growing fruit, vegetables and herbs close to busy roads or industrial areas.

Previous studies have found elevated concentrations of metals, including lead, in some edible plants grown near major traffic routes. Leafy herbs such as parsley and mint tended to accumulate more than root vegetables or legumes, while some crops grown within ten metres of busy roads exceeded European threshold values.

The researchers stress that this is not a reason to stop growing food at home. Instead, they say more research is needed to understand how garden location, barriers, vegetation and planting arrangements influence the transfer of airborne pollutants into soils and crops, particularly in heavily polluted neighbourhoods.

Cleaner air may involve trade-offs

The study also found that choosing the "right" plants is unlikely to be straightforward.

Rough, hairy or waxy leaves can be effective at trapping pollution particles, while conifers may capture more fine particles because of their dense evergreen foliage.

However, some species also release naturally occurring compounds that may contribute to secondary air pollution under certain conditions, while others produce highly allergenic pollen.

Even routine gardening practices, including mowing, pruning and using petrol-powered equipment, may influence air quality through emissions or the release of plant-derived compounds, although these effects remain poorly understood in domestic gardens.

Turning an everyday green space into a research priority

The authors say future research should focus on how pollution moves through small residential spaces, how plant type, density and placement affect exposure, and how air-quality benefits interact with biodiversity, cooling, flood management, food production and wellbeing.

Rather than recommending particular plants or garden designs, the paper argues that future guidance should be based on evidence gathered in real homes and neighbourhoods, rather than assumptions drawn from parks, street canyons and other larger green spaces.

Dr Corada-Pérez added,

Domestic gardens already support biodiversity, help cool our cities, reduce flood risk, provide space for growing food and improve our wellbeing. Understanding how air quality fits alongside those benefits could help us make better use of one of the most widespread - but least studied - forms of green infrastructure in our cities."

By filling this knowledge gap, the researchers believe domestic gardens could become a more meaningful part of future clean-air, climate resilience and public health strategies, while giving residents practical, evidence-based advice about how their own gardens can contribute to healthier urban environments.

Read the full review.