Benzene and Other Hazardous Air Pollutants in Consumer-Grade Natural Gas in the United Kingdom, Italy, and the Netherlands

While consumer-grade natural gas leaks contribute to methane-induced climate change, they can also degrade air quality both indoors and outdoors. However, limited leakage and gas composition data exist outside of North America. Here, we chemically characterized 78 unburned gas samples from residential stoves and measured stove-off natural gas leakage in 35 homes across seven cities in the United Kingdom, Netherlands, and Italy. Benzene, a known human carcinogen, was substantially elevated in unburned gas compared to North America (9 to 73 times higher on average), while sulfur-based odorants, which are added to natural gas to warn against explosivity, were lower. Stove-off methane leakage rates had a highly skewed, long-tailed distribution with an average of 46 mg/hr and a range from no detectable leak to 651 mg/hr. Modeling of indoor kitchen benzene enhancements from gas stove leaks showed potential for hazardous benzene exposure, often undetectable by odor. Eight percent of homes exhibited a stove-off leak that, combined with city-median benzene concentrations in gas, resulted in modeled benzene enhancements above the European Union’s annual limit value of 1.6 ppbv. Modeling of an outdoor distribution pipeline leak resulted in benzene concentrations over four times the European Union’s 200 ppbv occupational hazard limit and showed benzene enhancements up to 10 km away. These modeled indoor and outdoor enhancements are in addition to other sources of benzene exposure from cooking, smoking, gasoline, and leaks from other gas appliances or pipelines. The combination of high benzene and relatively low odorization in natural gas suggests that hazardous leaks are likely underreported in Europe. Natural gas leaks are not just a climate or explosion risk—they are an underrecognized public health issue.