New research confirms the presence of benzene in natural gas and the possibility of undetectable indoor leaks

New research shows that even people with an average sense of smell can live with a natural gas leak without knowing it. The study, published in Environmental Investigation Lettersfinds that small gas leaks can affect indoor air quality by introducing a number of dangerous air pollutants, including the carcinogen benzene, which researchers found in 97% of natural gas samples in North America.

“While these smaller leaks are not large enough to cause gas explosions, hard-to-smell 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 resolve, which can lead to a persistent source of benzene and methane indoors.”

The study is the first to assess whether gas leaks contain sufficient odorants to protect against elevated levels of benzene exposure, and provides the most comprehensive data to date on the composition of natural gas in homes.

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

“Our nose is the first and only line of defense against household gas leaks,” said PSE senior scientist Drew Michanowicz. “Given the variation in odor levels and the vast disparity in the ability to smell among the general public, our findings call into question the sole reliance on odor to protect people from gas leaks.”

On average, the gas delivered to homes in Vancouver, Los Angeles, Calgary and Denver had twice as much benzene as the other cities, while Vancouver’s benzene levels were almost fifty times higher than those of the city with the lowest concentration, Boston. Odor levels in Houston gas were about five times higher than those in Toronto, while neighboring cities New York City and Washington, DC appeared to use completely different fragrance products, indicating a lack of standardization.

On average, measured natural gas odor levels should alert most occupants to gas leaks that could lead to high benzene exposure; However, every household 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. In addition, improving leak detection through stricter odor standards or greater use of leak detection equipment, or reducing gas consumption altogether, can improve indoor air quality and public health.