New study confirms presence of benzene in natural gas and potential for undetectable indoor leaks

New research reveals that even people with an average sense of smell may be living with a natural gas leak and not know it. The study, published in Environmental Research Papersfinds that small gas leaks can affect indoor air quality by introducing a number of dangerous air pollutants, including carcinogenic benzene, which researchers found in 97% of natural gas samples across America North.

“While these smaller leaks are not large enough to cause gas explosions, hard-to-sniff leaks are common,” said lead author and PSE Healthy Energy scientist Sebastian Rowland. “The fact that they are so small makes them difficult to identify and fix, which can lead to a continuous indoor source of benzene and methane.”

The study is the first to assess whether gas leaks contain enough flavoring to protect against high levels of benzene exposure and provides the most complete data yet on the composition of residential natural gas.

Researchers from PSE Healthy Energy and Stanford University collected and analyzed 587 natural gas samples from 481 residences across 17 North American cities. The samples were tested for methane, hazardous air pollutants and sulfur-based odorants, and the researchers modeled the amount of gas that might leak undetected by a resident with an average sense of smell. Their findings confirm that benzene and other dangerous air pollutants are present in nearly all natural gas supplied to homes, buildings and businesses across North America.

“Our nose is the first and only line of defense against domestic gas leaks,” said PSE Senior Scientist Drew Michanowicz. “Given the variation in odor levels and the large disparity in olfactory ability in the general public, our findings really call into question the sole reliance on smell to protect people from gas leaks.”

On average, the gas delivered to homes in Vancouver, Los Angeles, Calgary and Denver had twice the levels of benzene than the other cities, with benzene levels in Vancouver nearly fifty times higher than that of the city with the lowest concentration , Boston. Flavor levels in Houston’s gas were roughly five times higher than Toronto, while neighboring cities New York and Washington, DC, appeared to use different flavoring products altogether, indicating a lack of standardization.

On average, measured natural gas odor levels should alert most residents to gas leaks that could lead to high benzene exposures; however, each family faces a different situation due to differences in personal olfactory sensitivity, ventilation rates, gas composition, and barriers to fixing leaks after detection.

The researchers suggest that regulators and consumers would benefit from greater transparency of natural gas composition, such as open access to natural gas composition data and regular sampling. Additionally, improving leak detection through stricter odor standards or increasing the use of leak detection equipment, or reducing gas use altogether can improve indoor air quality and public health.