Short-term priority: prevent leaks
By PSE HEALTHY ENERGY
“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 hard to identify and fix, which can lead to a
persistent indoor source of benzene and methane.”
Study Findings on Gas Composition and Odorants
The study is the first to assess whether gas
leaks contain enough odorant to protect against elevated levels of benzene
exposure, and provides the most comprehensive data to date on residential
natural gas composition. Researchers from PSE Healthy Energy and Stanford
University collected and analyzed 587 samples of natural gas from 481
residences 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 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 households, buildings, and
businesses throughout North America.
“Our nose is the first and only line of
defense against household-level gas leaks,” said PSE Senior Scientist Drew
Michanowicz. “Given the variation in odorant levels and the enormous disparity
in the ability to smell across the general public, our findings really call
into question the sole reliance on odor to protect people from gas leaks.”
Geographic Disparities in Benzene and Odorant Levels
On average, gas delivered to homes in
Vancouver, Los Angeles, Calgary, and Denver had twice the benzene levels than
the other cities, with benzene levels in Vancouver nearly fifty times greater
than that of the lowest concentration city, Boston. Odorant levels in Houston
gas were approximately five times higher than Toronto, whereas the neighboring
cities of New York City and Washington, D.C., appeared to use different odorant
products altogether, indicating a lack of standardization.
On average, measured natural gas odorant
levels should alert most occupants to gas leaks that can lead to high benzene
exposures; however, each household faces a different situation due to
differences in personal smelling sensitivity, ventilation rates, gas
composition, and barriers to fixing leaks after detection.
The research team suggests 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 odorization
standards or increased usage of leak-detecting devices, or reducing gas use
altogether can improve indoor air quality and public health.
Reference: “Downstream natural gas
composition across U.S. and Canada: implications for indoor methane leaks and
hazardous air pollutant exposures” by Sebastian T Rowland, Eric D Lebel,
Jackson S W Goldman, Jeremy K Domen, Kelsey R Bilsback, Angélica Ruiz, Jessie M
Jaeger, Lee Ann L Hill, Yannai S Kashtan, Colin Finnegan, Metta Nicholson,
Zutao Ouyang, Robert B Jackson, Seth B C Shonkoff and Drew R Michanowicz, 4
June 2024, Environmental Research Letters.
DOI:
10.1088/1748-9326/ad416c