Benzene and other hazardous air pollutants in consumer-grade natural gas in Europe

Consumer-grade natural gas leaks contribute to methane-induced climate change and can degrade air quality. However, limited leakage and gas composition data exist outside of North America. Here, we measured stove-off gas leakage in 35 homes and chemically characterized 78 unburned gas samples from residential stoves across seven cities in the United Kingdom, Netherlands, and Italy. On average, benzene in unburned gas was substantially elevated compared to North America (9 to 73 times higher), while sulfur-based odorants were lower. Modeling of indoor and outdoor benzene enhancements from gas leaks showed potential for hazardous benzene exposure, often undetectable by odor. Three of 35 homes exhibited a stove-off leak that, combined with city-median benzene in gas, resulted in modeled benzene enhancements above the European Union's annual limit value (1.6 ppbv). The combination of high benzene and relatively low odorization in natural gas suggests that hazardous leaks are likely underreported in Europe.