Cooking on a gas hob can create higher levels of indoor air pollution than found on one of the UK’s busiest roads, a study has found.
The research by Which? compared levels of two of the most damaging air pollutants – nitrogen dioxide (NO2) and fine particulate matter (PM2.5) – in the homes of four people with gas hobs, one person with an induction hob and on Marylebone Road in central London.
NO2 is a significant contributor to children developing asthma, as well as exacerbating other respiratory conditions in children and adults.
PM2.5 has been linked to the worsening or development of several diseases, including respiratory illnesses, lung cancer, an increased risk of heart disease and Parkinson’s disease.
The study, conducted in November 2024, found that levels of NO2 from a gas hob increased in line with the amount of cooking time and the number of gas rings used. Even when slow cooking a meal using one ring NO2 levels more than doubled.
Once levels of NO2 had spiked researchers found that they remained elevated for a significant time – often several hours.
The study suggests that people spending their evening in the same room where they have cooked could be exposed to sustained elevated levels of harmful pollutants well in excess of World Health Organization (WHO) guidelines.
The volunteer who used the induction hob experienced background levels of NO2, mainly from outdoor pollution.
During the study, average NO2 levels over an hourly mean near the Which? office on Marylebone Road reached 33 micrograms per cubic metre, while average PM2.5 over a 24-hour mean was 14 micrograms per cubic metre.
In contrast, three of the volunteers using a gas hob experienced PM2.5 peaks of more than 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.
Which? researchers calculated that one household averaged more than the WHO PM2.5 guidance limit for four days, while two other homes exceeded the limit for two days.
The PM2.5 base levels recorded before cooking ranged from between less than one microgram per cubic metre to about 20 micrograms per cubic metre.
In one scenario, the volunteers checked the air quality in an adjoining room, or in the living area if their house was open plan.
Levels of both NO2 and PM2.5 still reached high peaks, and elevated levels continued for several hours after cooking, showing that pollution spreads rapidly through the home.
PM2.5 levels returned to levels recorded before cooking within 45 minutes of doors or windows being opened in three out of five homes.
A Which? survey of just over 2,000 UK adults about air pollution found little awareness of the dangers posed by cooking. Only a quarter of those with gas hobs said they were concerned about the possible impact of on their health.
A study published last October found that NO2 exposure from gas cooking in the UK is linked to around 4,000 premature deaths annually, at a cost of £15.1bn per year.
Dr Monica Mateo-Garcia, of the Centre for Future Homes at Birmingham City University, advised consumers to use extractor fans that vent outside, and to open windows and doors while cooking as this helped “a quick decay of the indoor pollutants”.
Christian Pfrang, professor of atmospheric science at the University of Birmingham, also advised consumers to always use extractor fans when cooking, noting research has found many people do not.
He warned that if indoor pollution was not removed quickly it would disperse throughout the home, for example, into bedrooms where people might spend more time.
“They might spend 20 minutes cooking, but then might be exposed to elevated levels for eight or nine hours, which really causes health issues, especially if you’re vulnerable or elderly or a child,” he added.
