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Cooking on a gas hob can generate higher levels of air pollution than those found on a busy London road, a snapshot investigation by consumer group Which? has revealed.
The findings raise concerns about the potential health impacts of gas cooking, particularly for children and those with respiratory conditions.
In November, Which? equipped five volunteers – four with gas hobs and one with an induction hob – with air quality monitors to assess the impact of everyday cooking on indoor pollution levels.
Participants, all using extractor hoods, were asked to perform various cooking tasks in addition to their normal routines over a week, keeping windows and doors closed except for one test involving full kitchen ventilation.
The investigation focused on nitrogen dioxide (NO2) and fine particulate matter (PM2.5), two of the most harmful air pollutants.
NO2 is linked to childhood asthma development and can worsen respiratory problems in both children and adults.
PM2.5, capable of penetrating deep into the lungs and bloodstream, is associated with various health issues, including respiratory illnesses, lung cancer, heart disease, and Parkinson’s disease.
Which?’s findings showed a direct correlation between gas hob use and NO2 levels, with levels rising in proportion to the duration and intensity of gas usage.
In a “slow cooking” scenario using a single burner, NO2 levels more than doubled for all participants with gas hobs.
Furthermore, these elevated levels persisted for several hours after cooking, suggesting prolonged exposure risks, especially in open-plan homes where people might spend their evenings in the same room where they cooked. This sustained exposure could significantly exceed World Health Organisation (WHO) guidelines.
Previous studies have highlighted the high levels of NO2 put out by gas hobs – a by-product of burning natural gas.
In line with this, the NO2 levels experienced by the volunteer in Which?’s study who used the induction hob were background levels, mainly from outdoor pollution.
Over the same period, average NO2 levels over an hourly mean near the Which? office on London’s busy Marylebone Road reached 33 micrograms per cubic metre, while average PM2.5 over a 24-hour mean for November 2024 was 14 micrograms per cubic metre.
In Which?’s experiment, three of the volunteers using a hob experienced PM2.5 peaks of over 100 micrograms per cubic metre on several occasions, and one volunteer experienced a peak PM2.5 of nearly 650 micrograms per cubic metre – the WHO 24-hour mean guidance limit is 15 micrograms per cubic metre – when frying padron peppers.
Another experienced nearly 600 micrograms per cubic metre when frying peppers and tomatoes, and two volunteers had peaks of nearly 500 micrograms per cubic metre when cooking a fry-up.
Overall, base levels before cooking varied from less than one microgram per cubic metre to no more than around 20 micrograms per cubic metre.
Which? experts averaged out the PM2.5 over a 24-hour period for the five days each person used the air-quality monitors, finding one household averaged over the WHO guidance limit for four days, while two other homes exceeded the limit for two days.
For one of the cooking scenarios, Which? also asked people to move their monitors into an adjoining room, or into the living area if their house was open plan.
Levels of both NO2 and PM2.5 still reached high peaks and elevated levels for some hours afterwards, showing that air pollution spreads through the home rapidly.
Which? also asked all volunteers to fry food in oil for 10 minutes, but with all windows and any external doors open during frying and for 10 minutes afterwards.
The average peak PM level reached by the five participants was 27 micrograms per cubic metre, far less than in all the other frying scenarios, whereas the next lowest average for any of the frying scenarios Which? carried out was 100 micrograms per cubic metre.
Crucially, PM levels returned to those recorded before cooking with doors or windows open in three out of five homes within 45 minutes.
Which? energy and sustainability editor Emily Seymour said: “It’s shocking to think that something as routine as cooking dinner could be releasing harmful pollutants into our own homes, but our snapshot research shows that once it spikes, air pollution can spread rapidly through the house and linger for long periods of time.
“We still don’t know the full impact of indoor pollutants on our health but if it is something you are concerned about, ventilating by using your extractor hood and opening windows can make a big difference. If you are using a gas hob you could consider switching to induction when you next need to replace your hob.”
Deltapoll surveyed 2,002 UK adults between November 29 and December 2.
