Gas boilers have overtaken traffic as the single largest contributor to air pollution in London, according to a landmark new study that is expected to have wide-reaching implications for urban heating policy across the UK.
The peer-reviewed research, led by Professor James Lee of the University of York and the National Centre for Atmospheric Science, reveals that emissions from domestic and commercial boilers now account for the majority of nitrogen oxides (NOx) in the capital. The findings raise serious concerns about the impact of heating systems on public health and air quality in Britain’s cities.
Using long-term atmospheric monitoring data from central London, the study pinpoints combustion-based heating—specifically the burning of natural gas—as the main driver of harmful urban air pollutants. These emissions not only contribute to respiratory problems but are also linked to cardiovascular disease and premature death.
“Replacing natural gas with zero-emission technologies such as electric heat pumps would locally eliminate both greenhouse gas and pollutant emissions,” said Professor Lee. “Heating is the next big frontier in our fight against poor air quality—and this study makes it clear that we must act now.”
The findings are likely to resonate far beyond London. Cities with similar infrastructure and climates are expected to share comparable emissions profiles, reinforcing the case for large-scale electrification of heating systems across the UK.
Policy momentum and international precedent
Air pollution caused by domestic heating is already being addressed abroad. In California and the San Francisco Bay Area, all new boilers are required to be zero-NOx from 2027. The legislation is expected to deliver up to $530 million per year in public health savings through reduced damage from NOx exposure.
But in the UK, experts argue that policy and regulatory action is lagging.
Martin Lewerth, Group CEO of Aira, a pan-European leader in heat pump solutions, welcomed the study as a wake-up call. He said: “This research confirms what many of us in the clean heating sector have long suspected—gas boilers are not only inefficient but damaging to our health. The UK government must take urgent action to cut the red tape that is slowing down the transition to clean alternatives like heat pumps. “We know the technology works, and it’s ready to scale. What we need now is decisive policy that prioritises clean air and public health.”
A call to action for the UK government
The study recommends that heating-related emissions be treated with the same urgency as transport emissions, especially in densely populated urban centres. While schemes like the Ultra Low Emission Zone (ULEZ) have helped reduce vehicle-related air pollution, similar ambition has yet to be applied to building emissions.
With households and businesses still heavily reliant on natural gas, campaigners say a well-supported shift to heat pumps and other clean technologies could dramatically improve urban air quality, cut greenhouse gases, and reduce long-term health costs.
The government’s own net zero strategy includes targets to phase out new gas boilers by 2035, but experts warn that unless these efforts are accelerated and bureaucracy is reduced, the UK risks falling behind both its environmental targets and its duty to safeguard public health.
For businesses, policymakers, and the property sector, the message is clear: the future of urban heating must be clean—and the time to act is now.
