Benzene Fumes Present in Nearly All Natural Gas Emissions in U.S. Homes: Study

Hundreds of thousands of households in the U.S. and Canada may regularly experience small natural gas leaks containing benzene, a known cancer-causing chemical, which are often undetected, according to the findings of a new study.

Researchers from Stanford University report that natural gas leaks are extremely common in North America, according to findings published this week in the journal Environmental Research Letters.

While natural gas contains odorants designed to help alert those nearby of a potential leak, researchers warn that the average person’s sense of smell struggles to detect the leak, increasing the risk of dangerous exposure. This not only increases the risk of injuries caused by fires and explosions from natural gas leaks, but occupants may also be unaware that they are being exposed to potentially toxic chemicals, like benzene and other substances.

Benzene Exposure Risks

Benzene is a colorless chemical with a slightly sweet odor. It is highly flammable and often part of the chemical makeup of residential natural gas. If a natural gas leak occurs, the benzene can light on fire and lead to an explosion.

However, benzene is also known to be toxic. Benzene from indoor gas stove leaks has been linked to the formation of carbon monoxide, formaldehyde, and nitrogen dioxide–chemicals that are also toxic to human health.

Exposure to benzene emissions themselves can damage the immune system and has been linked to an increased risk of several fatal forms of cancer and life-threatening health conditions, such as acute myeloid leukemia (AML), Chronic Myelogenous Leukemia (CML), Acute Lymphocytic Leukemia (ALL), Chronic Lymphocytic Leukemia (CLL), Hairy Cell Leukemia (HCL), Non-Hodgkin’s Lymphoma, Multiple Myeloma, Myelodysplastic Syndrome (MDL), Myelofibrosis, Myeloid Metaplasia, Aplastic Anemia and Thrombocytopenic Purpura. Long-term side effects of benzene exposure have also been proven to cause anemia.

In this new study, researchers from Stanford University and the PSE Healthy Energy facility, led by PSE scientists Sebastian Rowland and Eric D. Lebel, took samples from 587 unburned natural gas sources from 481 residences across 17 North American cities. They analyzed the samples for hydrocarbons, hazardous air pollutants, and organosulfur odorants.

Researchers found that current U.S. and Canadian emissions inventories are missing 25,000 and 4,000 pounds of benzene per year, most likely due to natural gas leaks occurring in households. Looking at the samples appeared to confirm that, with nearly 97% of natural gas samples containing benzene, with large variations in levels between cities.

The data indicated Vancouver, Los Angeles, Calgary, and Denver had twice the average levels of benzene concentrations than the samples from other cities. Vancouver had an average benzene level that was more than 50 times higher than that of the lowest concentration city, Boston.

However, Houston had levels of odorants five times higher than Toronto. And New York City and Washington D.C. used completely different odorant products, making comparisons difficult. The samples also contained other hazardous air pollutants, which were present in nearly all natural gas supplied to households, buildings, and businesses throughout North America.

Researchers concluded the findings highlight a lack of standardization for natural gas and the chemicals meant to give it a detectable smell.

Most Natural Gas Leaks Undetected

The lack of standardization may be why the data indicated the odors added to natural gas to aid in its detection did not appear to work in many cases, the researchers speculated. The ability to smell a gas leak varied based on the amounts and types of odorants used. However, even some larger leaks were largely undetectable by smell, the researchers determined.

The data indicated most of the leaks were small and would never lead to an explosion. On the other hand, these small leaks may never be fixed because they cannot be detected. This could result in a persistent source of exposure to benzene and other chemicals, like methane, the researchers determined.

The findings come after a study published earlier this year in Science Advances concluded roughly 50,000 cases of childhood asthma are linked to natural gas leaks from household appliances, like stoves.

A study published in 2023, also by Stanford University researchers, found that levels of benzene emitted by gas stoves in the average American home were similar to the levels of benzene found in secondhand cigarette smoke. The findings warned that the exposure to the benzene posed similar health risks to residents, including the risk of cancer.

“Given methane’s global warming potency, benzene’s toxicity, and wide variation in smelling abilities, our findings highlight the deficiencies regarding the sole reliance on odor to alert and protect all occupants from indoor leaks,” Rowland and Lebel wrote.

The researchers determined that other methods of detecting natural gas leaks are needed besides odor-causing agents, and emphasized the need for natural gas standardization across the industry.