Natural gas distributed at home has a lower concentration of various chemicals associated with cancer, a new study has found. Researchers have also found an odd amount of odor – a substance that gives natural gas its characteristic “rotten egg” odor – which can increase the risk of undetected small leaks.
The study, published in the Journal of Environmental Science and Technology, adds to a growing body of research that links the distribution and use of natural gas to harmful consequences for public health and the climate.
Most previous studies have documented oil and gas extraction where pollutants are present, but “there have been fewer studies as you work your way down the supply chain,” said study lead author Drew Michanovic, “where we actually use our homes.”
For more than 16 months, researchers have collected 234 samples of unfinished natural gas from 69 homes in the Boston metropolitan area that received natural gas from three suppliers. They found 21 “air toxins” – including benzene, which was detected in 95 percent of the samples – an environmental protection agency classification of known or suspected hazardous pollutants known to cause cancer, birth defects or adverse environmental effects.
According to the Centers for Disease Control and Prevention, short-term exposure, especially to high doses of benzene, can cause drowsiness, dizziness, headaches, and eye and skin irritation. Long-term exposure can increase the risk of certain cancers, such as blood disorders and leukemia.
The highly combustible chemical is colorless or light yellow, and is found in products made from coal and oil, including plastics, resins, and nylon fibers, as well as some types of rubber, paints, and pesticides. It is available in regular vehicle exhaust, tobacco smoke and gasoline.
The researchers found that the concentration of benzene in natural gas samples was “much lower than the amount of gasoline.” Michanovic said during a conference call with reporters on Friday. Nevertheless, he said, the search is of concern because “natural gas is widely used in society and in our interior spaces.”
According to the EPA, Americans spend more than 90 percent of their time indoors, where the concentration of some pollutants can be two to five times higher than the concentration outside.
Benzene is a carcinogen, and as exposure is added over time, some experts suggest that there is no safe level of exposure.
The researchers said the goal of their study was to identify the presence and concentration of specific hazards and that more research was needed to understand health risks.
“The biggest source of benzene in most people’s lives is cars and gasoline from smoking,” said Rob Jackson, an earth scientist at Stanford University. “On the other hand, there’s too much unnecessary benzene in your home.”
Imperfect natural gas contains an odd amount of odor or a substance that gives off a noticeable odor, the researchers said. Methane, the main component of natural gas, is odorless, so odors are added regularly to help detect leaks.
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“If there is less odor in the natural gas flow, they are more likely to have a larger leak without the odor,” Dr. Michanovic said in a call on Friday.
When released into the atmosphere, methane is a particularly powerful greenhouse gas. It could heat the planet more than 80 times the same amount of carbon dioxide over a 20-year period. Oil and gas companies have been on fire in recent years for the release of large-scale, invisible methane.
Across the country, a growing number of cities are trying to cut off natural-gas connections to homes and businesses in favor of electric alternatives, mostly citing the effects of continuing to burn fossil fuels.
Curtis Nordgaard, a pediatrician and co-author of the study, said the new study suggested that natural gas leaks contain not only methane, but also toxic substances in the air that could be harmful to public health. “We want to reconsider these leaks as not just a climate issue, but a health issue,” he said.
Dr. Nordgaard is a senior scientist at PSE Healthy Energy, a nonprofit research institute that focuses on climate impacts on public health and energy production, such as Dr. Michanovic.
With this study, the researchers said they hoped to fill a gap in gas availability data availability and transparency. Pipeline operators and gas suppliers in the United States typically inspect gas composition, in line with the recommendations of the North American Energy Standards Board, an industry body that sets standards for the natural gas and electricity markets.
However, gas composition tests typically measure the 16 most abundant components of natural gas. This list does not include some of the ingredients identified by researchers, such as benzene.