The natural gas delivered to homes has low concentrations of several chemicals linked to cancer, a new study found. Researchers also found inconsistent levels of odorants – substances that give natural gas its characteristic “rotten egg” smell – which could increase the risk of small leaks going undetected.
The study, which was published in the journal Environmental Science & Technology, adds a growing body of research that links the distribution and use of natural gas to detrimental consequences for public health and the climate.
Most prior research has documented the pollutants present where oil and gas extraction takes place, but there are “fewer studies as you work your way down the supply chain,” said Drew Michanowicz, lead author of the study, looking at “where we actually are. use it, in our homes. “
Over 16 months, researchers collected 234 samples of unburned natural gas from 69 homes in the Boston metropolitan area that received three suppliers of natural gas. They found 21 “air toxics” – an environmental protection agency classification of hazardous pollutants known or suspected to cause cancer, birth defects or adverse environmental effects – including benzene, which was detected in 95 percent of the samples.
Short-term exposure to high levels of benzene in particular can lead to drowsiness, dizziness, headaches and irritation of the eyes and skin, according to the Centers for Disease Control and Prevention. Longer-term exposure can increase the risk of blood disorders and certain cancers like leukemia.
The most flammable 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 rubbers, dyes and pesticides. It is also regularly found in vehicle exhaust, tarmac smoke and gasoline.
The concentrations of benzene that the researchers found in natural gas samples were “much lower than the amount in gasoline,” Dr. Michanowicz said on Friday during a conference call with reporters. Even so, he said, the finding is related since “natural gas is so widely used in society and in our indoor spaces.”
Americans spend more than 90 percent of their time indoors, according to the EPA, where concentrations of some pollutants can range from two to five times as high as outdoor concentrations.
Benzene is a carcinogen, and exposure over time adds up, leading some experts to suggest that there is no safe level of exposure.
The researchers said that the goal of their study was to identify the presence and concentration of certain hazards, and that more research is needed to understand the health risks.
“The biggest sources of benzene in most people’s lives are gasoline from cars and smoking,” said Rob Jackson, an earth scientist at Stanford University who didn’t work on the study. “On the other hand, any unnecessary benzene in your home is just too much.”
The unburned natural gas also contains inconsistent levels of odorants, or substances that give off a perceptible odor, the researchers said. Methane, the main component of natural gas, is odorless, so odorants are routinely added to help detect leaks.
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“If there is less odorant in the natural gas stream, there is a higher potential for larger leaks to exist without a smell to them,” Dr. Michanowicz said in the Friday call.
When released into the atmosphere unburned, methane is a particularly potent greenhouse gas. It can warm the planet more than 80 times as much as the same amount of carbon dioxide over a 20-year period. Oil and gas companies have come under fire in recent years for large-scale, invisible releases of methane.
Across the country, a growing number of cities are trying to phase out natural-gas hookups in homes and businesses in favor of electric alternatives, while citing the impact of emissions to continue to burn fossil fuels.
The new research suggests that natural gas leaks are not just releasing methane, but also air toxics that can be detrimental to public health, said Curtis Nordgaard, a pediatrician and study co-author. “We might want to rethink those 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 focused on the public health and climate impact of energy production, as is Dr. Michanowicz.
With this study, the researchers said they hoped to fill in the gaps in the availability and transparency of gas composition data. Pipeline operators and gas suppliers in the United States generally test the composition of gas, consistent with recommendations from the North American Energy Standards Board, an industry organization that sets standards for the natural gas and electricity marketplace.
However, the gas composition tests usually measure only the 16 most abundant constituents of natural gas. That list does not include some of the components identified by researchers, like benzene.