High levels of the carcinogen benzene have been discovered in the domestic gas supply of four UK cities, according to researchers at Stanford Doerr School of Sustainability. The substance, which occurs naturally in oil and gas fields, has no safe exposure level according to the World Health Organisation and is associated with leukaemia and DNA damage at high concentrations.
Between 2023 and 2024, researchers collected 40 gas samples from London, Edinburgh, Manchester and St Neots in Cambridgeshire, as part of a wider study across the UK, Netherlands and Italy. The highest benzene reading was found in London at 200 parts per million by volume (ppmv), significantly above the EU annual limit of 1.6 parts per billion by volume (ppbv). Edinburgh and Manchester recorded maximum levels of 57ppmv and 53ppmv respectively, while the lowest UK reading was 4ppmv, also in London.
Dr Tamara Sparks, lead author and air quality scientist at PSE, said: 'Given these high concentrations, a lot of people are likely being chronically exposed to benzene without knowing it.' The study, published in Environmental Research Letters, also found that 40 per cent of kitchens tested across the three countries had gas leaks when cookers were switched off.
Modelling estimated that about 9 per cent of homes visited had leaks large enough to exceed a national exposure limit for benzene. The calculated benzene exposure from larger UK leaks is worse than living with a smoker, in terms of benzene alone. For context, a person smoking 20 cigarettes a day has an estimated four-times greater intake of benzene than a non-smoker.
Researchers also found that odourant levels added to gas to help detect leaks were too low in the UK and Netherlands to alert most people to leaks large enough to reach unhealthy limits. In London, benzene concentrations from a leak could reach 62ppbv before odour indicates a problem – almost 40 times the EU annual limit.
Dr Rachel Huxley, head of mitigation at the Wellcome Trust, said: 'We expect our homes to be the safest place we spend our time. This study shows that everyday use of gas can put people at unnecessary health risks.' A Health and Safety Executive spokesperson said robust regulations are in place and any suspected leak should be reported to the National Gas Emergency Service.
