Recent research indicates a high risk of undetected natural gas leaks in homes in North America, where dangerous pollutants like benzene are commonly present. The study calls for better leak detection standards and greater transparency into the composition of natural gas to improve indoor air quality and safety.
The results highlight the importance of implementing more rigorous standards for natural gas odorization and leak detection.
New findings reveal that people with an average sense of smell may be unknowingly living with natural gas leaks, according to a peer-reviewed study in Environmental Research LettersMinor leaks can deteriorate indoor air quality by emitting various dangerous pollutants, such as benzene, a carcinogen detected in 97% of natural gas samples in North America.
“While these small leaks are not large enough to cause gas explosions, hard-to-detect leaks are common,” said Sebastian Rowland, lead author and PSE healthy energy scientist. “The fact that they are so small makes them difficult to identify and repair, which can lead to a persistent source of benzene and methane indoors.”
Results of a study on the composition of gases and odors
This study is the first to assess whether gas leaks contain enough odor to protect against high levels of benzene exposure and provides the most comprehensive data to date on the composition of residential natural gas. Researchers from PSE Healthy Energy and Stanford University collected and analyzed 587 natural gas samples from 481 homes in 17 cities across North America. The samples were tested for methane, hazardous air pollutants, and sulfur-based odors, and the researchers modeled how much gas could leak undetected 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 noses are the first and only line of defense against household gas leaks,” said Drew Michanowicz, PSE’s principal scientist. “Given the variation in odor levels and the huge disparity in smelling ability across the general population, our findings really call into question the sole reliance on smell to protect people from gas leaks.”
Geographic disparities in benzene and odor levels
On average, gas delivered to homes in Vancouver, Los Angeles, Calgary, and Denver contained twice as much benzene as other cities, with Vancouver’s benzene levels nearly fifty times higher than those in the city with the lowest concentration, Boston. Odor levels in Houston’s gas were about five times higher than those in Toronto, while neighboring New York and Washington, D.C., appeared to use entirely different odorants, indicating a lack of standardization. On average, measured odor levels in natural gas should alert most occupants to gas leaks that can lead to elevated benzene exposure; however, each home faces a different situation due to differences in personal olfactory sensitivity, ventilation rates, gas composition, and barriers to repairing leaks once they are detected.
The researchers suggest that regulators and consumers would benefit from greater transparency about the composition of natural gas, such as open access to data on natural gas composition and regular sampling. Additionally, improving leak detection through stricter odorization standards or increased use of leak detection devices, or even reducing gas use altogether, can improve indoor air quality and public health.
