Scientists have discovered that hazardous levels of carcinogenic benzene can leak from pipes, stoves and other appliances fuelled by domestic gas in Europe, even when switched off.
Making “conservative calculations”, the US researchers estimated that hundreds of thousands of people in the UK and Netherlands, countries where contamination was the highest, were exposed to levels of benzene well above national and EU regulatory recommendations.
In the worst affected homes “modelled benzene exposure . . . is worse than living with a smoker”, said the scientists from Stanford University and PSE Healthy Energy, an independent research institute in California.
The researchers first analysed unburned gas from kitchen stoves in a sample of almost 80 houses in the UK, Netherlands and Italy. In London and Amsterdam they found average benzene levels 60 to 70 times higher than in parts of North America.
Then they sampled the air in each home for gas that escaped from pipes and joints when the stove was off. Low-level leaks were found in 40 per cent of the kitchens, in quantities too small for people to detect.
The researchers calculated that in the UK benzene exposure could rise to nine times above the national safe limit before most people could smell a leak from the sulphur-based chemicals that suppliers add to alert consumers to escaped gas.
The European study followed a similar project in the US and Canada. “We were surprised by how much higher the levels were than anything we observed in North America,” said Tamara Sparks, lead author of the study published in Environmental Research Letters.
Geology appeared to be the principal reason for the contrasting readings across the Atlantic, said Drew Michanowicz, project leader at PSE.
European natural gas extracted from North Sea and Norwegian fields naturally contains much more benzene than American sources.
“The levels of benzene we found in the distribution system gas in the UK and the Netherlands are frankly eye-popping,” said Seth Shonkoff, PSE executive director. “That means even a small leak can pose significant health risks quickly indoors and outdoors.”
Frank Kelly, professor of community health at Imperial College London who was not involved in the study, said he did not believe the authors had exaggerated the risks.
“These findings are really quite worrying, adding to the other issues of raised indoor particle and nitrogen dioxide concentrations in homes with gas supplies as they point to a hidden source of carcinogenic exposure,” he said. “Benzene has no safe level, yet it was found in every gas sample tested.”
Future Energy Networks, the body representing UK gas distributors, said any potential health and safety concerns were taken seriously and it would consider the study findings.
“Steps are continually taken to mitigate risks, including investment in mains replacement and leakage reduction, operating a gas emergency service in response to public reports of gas outside and inside properties, and working to strict gas quality specifications,” it said.
Benzene is a carcinogen linked particularly with leukaemia. There was no epidemiological evidence to demonstrate the adverse health effects of benzene directly from domestic gas leaks, said PSE’s Michanowicz, as the issue was newly recognised. Chronic leaks would affect people alongside other pollutants, he noted, including from cooking with gas.
“A lot of people don’t know that in developed countries the air we breathe indoors may be dirtier than outdoor air,” he said.
While people remained dependent on gas for cooking and heating from sources with elevated benzene, it would be impossible to eliminate the problem, the researchers said, though gas suppliers could add more odorants to increase the chance of people smelling leaks that could be fixed. Householders should also arrange adequate ventilation of kitchens.