Relevant research article summaries

The presence of hazardous air pollutants (HAPs) entrained in end-use natural gas (NG) is an understudied source of human health risks. Researchers performed trace gas analyses on 185 unburned NG samples collected from 159 unique residential NG stoves across seven geographic regions in California and analysed commonly detected 12 HAPs with significant variability across region and gas utility. Mean regional benzene, toluene, ethylbenzene, and total xylenes (BTEX) concentrations in enduse NG ranged from 1.6 ppmv to 25 ppmv-benzene alone was detected in 99% of samples, and mean concentrations ranged from 0.7 ppmv -12 ppmv. By applying previously reported NG and methane emission rates throughout California's transmission, storage, and distribution systems, researchers estimated statewide benzene emissions of 4,200 kg/yr that are currently not included in any statewide inventories and is equal to the annual benzene emissions from nearly 60,000 light-duty gasoline vehicles. Additionally, NG leakage from stoves and ovens while not in use can result in indoor benzene concentrations that can exceed the California Office of Environmental Health Hazard Assessment 8-h Reference Exposure Level of 0.94 ppbv-benzene concentrations comparable to environmental tobacco smoke. This study supports the need to further improve our understanding of leaked downstream NG as a source of health risk.