June 28, 2022: This report has been updated to reflect additional comments from the American Gas Association.
The researchers, led by Harvard’s TH Chan School of Public Health, report that samples of natural gas taken before burning in homes in the Boston area for cooking contained 296 compounds, including 21 that are toxic to humans.
Toxic compounds include hexane, toluene, heptane, cyclohexane and benzene, a known carcinogen.The researchers also found that levels of so-called odors added to natural gas as a safety precaution vary and may not be detectable by the human nose, suggesting that federal guidelines need to be adjusted to address this inconsistency, they write.
The results, published Tuesday in the journal Environmental Science and Technology, add to a growing body of research on the potential health and climate risks of natural gas, even as reliance on the fuel increases.
The study comes as some cities and states are beginning to ban gas-fired equipment in new buildings in favor of electrical equipment.In January, researchers at Stanford University reported far more methane leaks from residential gas stoves than previously thought, with a 20-year climate impact equivalent to the carbon dioxide emissions of half a million cars.They also wrote that combustion pollutants released from combustion gases in homes may trigger respiratory illnesses.
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About half of American households use natural gas for cooking and heating every day.With every click of the furnace and turn of the thermostat, consumers are harnessing the energy of natural gas pipelines hundreds or even thousands of miles from their original source.
Natural gas is primarily methane, a greenhouse gas with a warming ability more than 80 times that of carbon dioxide over a 20-year period.However, when burned, methane produces less carbon dioxide than burning coal, so it is promoted as a “bridge fuel” in the energy transition.
Of the 234 samples collected from 69 families, 95 percent had low levels of benzene, which has been linked to anemia, decreased immune function and cancer.The presence of benzene and other toxic compounds raises questions about the health effects of natural gas in households, but not a cause for alarm, said Drew Michanowicz, a visiting scientist at the Center for Climate, Health and the Global Environment and lead author of the study.new research.
The study looked only at the presence of harmful substances such as benzene before natural gas was combusted, not whether household users were exposed to these compounds in ambient air.
The findings should prompt scientists and energy experts to consider whether natural gas is harming the public in ways that health researchers now understand, Michanowicz said.”What is the cost of this system?” he asked.
Rob Jackson, a professor of Earth system science at Stanford University and co-author of a January study that found gas stoves leaked more methane than expected, said the new Harvard study will help provide scientists and policymakers with better insights into indoor air pollution. overall data.natural gas source.
“This [new] study is a fascinating addition to other studies on indoor pollutants from gas combustion,” Jackson said.
Ongoing research is looking at the levels of each toxic compound in natural gas used in Boston-area homes, how much their owners are actually exposed to, and whether those levels pose a significant health risk.The researchers say this is the first step in determining the health risks of gas consumers during stove use and when gas leaks in their homes.Gas leaks occurred in 1 in 20 homes visited in the study, prompting the researchers to advise consumers to follow up with experts.
“Many households may have low-level leakage,” said Curtis Nordgaard, a senior scientist at PSE Healthy Energy at the Research and Policy Institute and co-author of the new study.When their sum is added up in a metro area like Boston, “it could be significant,” he said.
“While combustion emissions from gas stoves, ovens and cooktops contribute to some degree of recognized emissions pollutants, The risks to respiratory health from natural gas stoves are not documented by regulatory and advisory bodies and organisations charged with protecting the health and safety of residential consumers.”
A broader statement from the Rubin Society on Tuesday said any traces of benzene that could leak into a room would be “below conservative health-based screening levels” and “only a fraction of the typical background levels of benzene outdoors” and indoor air.”
The gas industry conducts “standard tests” on natural gas that “consistently show that natural gas also contains trace amounts of volatile organic compounds (VOCs),” the statement said.
“Given the very low levels of volatile organic compounds found in natural gas,” the statement said, “the temporal and spatial variations reported by the authors are primarily of academic interest.”
Occupational hazards can be more serious than household use, Nordgaard said.For example, people who work in commercial kitchens may be more exposed to harmful compounds in the gas.Time of year may also increase potential exposure.In Boston, concentrations of harmful compounds peaked in winter, eight times higher than in summer.
There could be multiple reasons for this winter peak, Michanowicz said.Increased demand for natural gas heating in winter, coupled with people spending more time indoors with less ventilation.Natural gas sources may also vary seasonally, and different wells may naturally contain higher concentrations of benzene.
In addition to potential public health impacts, characterizing the gases entering homes can influence decisions around climate change.”Cooking with a natural gas flame is the closest link to climate change we’ve ever imagined,” Michanowicz said.
Pipelines that start at fracking wells across the country “actually end right where the kitchen starts,” he said.A greenhouse gas, methane is the second-largest contributor to global warming after carbon dioxide, reaching record levels in the atmosphere last year.Stopping methane from leaking into the atmosphere from stoves, water heaters and, most commonly, pipes and oil and gas wells, is critical to combating climate change.
In Boston, natural gas is piped from wells located in the southern United States or western Canada.For the study, the researchers focused on three major natural gas suppliers: Algonquin Gas Transmission System, operated by Spectra Energy Partners, Kinder Morgan’s Tennessee Gas Pipeline, and Marine and Northeast owned by Spectra Energy Partners, Emera Inc. and ExxonMobil pipeline.
While methane is about 80 times more potent than carbon dioxide, it has a relatively short lifespan, remaining in the atmosphere for only 20 years (carbon dioxide remains in the atmosphere for centuries).So reducing methane emissions now will help countries meet their 2050 goal of curbing global warming more quickly.
Home Energy co-executive director Zeyneb Magavi said that while transitioning to electric and induction stoves is the most complete way to prevent any potential harm from using gas, there are simple, more affordable actions consumers can take now to reduce exposure.Efficiency team and co-author of the Harvard study.
Magavi recommends using a range hood with outward ventilation when cooking with a gas hob.In the absence of vents, opening windows will also increase ventilation.
Instead of replacing their gas ranges right away, consumers can plan to transition to electric ranges over time and save money for new appliances, she said.In homes with poor ventilation, buying inexpensive induction heating panels is another option, Magavi said.
Increasing ventilation and air filtration in new and existing buildings is also a good precaution, Magavi said.
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A better understanding of indoor air quality and gas consumption is imperative through more data and transparency, Magavi said.This includes information from gas companies about the actual composition of consumer natural gas.
Jackson, a Stanford University researcher, wants utilities to make more gas composition data publicly available as a public service.Companies currently publish information on the main components of their gases, such as hydrogen, oxygen and sulfur.Other levels were classified as general impurities, but the chemical concentrations were not as described in the Harvard study.
Finding and fixing indoor gas leaks can limit potential health impacts and improve safety, Magavi said.Residents and first responders may need more sensitive gas detectors to alert them of any leaks, as the new study found that the sulphurous smell of natural gas isn’t always detectable.
All samples in the study met federal requirements for odor levels, which are added to the gas to make dangerous leaks easier to spot.Even so, the authors used previous natural gas leak data to estimate average methane concentrations.They estimate that current standard odor levels may not be enough for humans to smell the average concentration of methane leaking from stoves.The study concluded that this may indicate that regulators need to raise odor levels to detect leaks that are currently undetected.
Hannah Loss is a New York City and Boston journalist with interests in ecology, infrastructure and agriculture.She is a graduate student in the NYU Science, Health and Environmental Reporting Program.Previously, she has worked in science documentaries and broadcast production and scientific conference programming.She studied Environmental Studies and English at Tufts University.
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Post time: Jun-30-2022