Every day, millions of Americans rely on natural gas to power appliances such as kitchen stoves, furnaces, and water heaters, but until now very little data existed on the chemical makeup of the gas once it reaches consumers.
A study led by Visiting Scientist, Drew Michanowicz, at Harvard T.H. Chan School of Public Health found that gas used in homes throughout the greater Boston area contains at least 21 different hazardous air pollutants that may impact air quality and health, wherever natural gas is leaked. The research, published in Environmental Science & Technology, is the first to test for health-damaging air pollutants in unburned natural gas when it is used in our homes.
Researchers collected over 200 unburned natural gas samples from 69 unique kitchen stoves and building pipelines across Greater Boston between December 2019 and May 2021. The research team included PSE Healthy Energy, Atmospheric and Environmental Research AER, Gas Safety Inc., Boston University, and Home Energy Efficiency Team (HEET).
- Consumer-grade natural gas supplied to Massachusetts contains varying levels of at least 21 different hazardous air pollutants, as defined by the U.S. EPA, including benzene, toluene, ethylbenzene, xylene, and hexane.
- Concentrations of hazardous air pollutants in natural gas varied depending on location and time of year, with the highest concentrations found in the winter.
- Based on odorant concentrations, small leaks can be undetectable by smell – leaks up to 10 times naturally occurring levels may be undetectable, equating to a methane concentration of about 20 parts per million.
Actions that policymakers and individuals can take to mitigate health risks posed by natural gas used in homes:
- Gas pipeline companies could be required to measure and report more detailed information on the composition of natural gas, specifically differentiating non-methane volatile organic compounds such as benzene and toluene.
- Gas utility providers could be required to routinely measure and report natural gas odorant content to customers similar to informational postings often produced by interstate gas pipeline companies.
- State regulations could require direct measurement of leaked, unburned natural gas in ambient air to be included in emissions inventories and to better determine public health risks.
- The Consumer Product Safety Commission has the authority to set performance standards for gas stoves and ventilation hoods to limit air pollutant emissions.
- Home inspectors and contractors could be required to perform natural gas-appliance leak detection surveys or to measure for ppm-range methane, similar to radon tests done prior to the completion of a real estate transaction.
- Given the importance of odorants in detecting gas leaks, federal natural gas odorization regulations could be updated so that natural gas is odorized to meet much lower detection levels than the current 1/5th the lower explosion limit (detectable at ~1% methane).
- Because small leaks may evade our sense of smell, getting an in-home natural gas leak detection survey performed by a licensed plumber or heating, ventilation, and air conditioning (HVAC) contractor can verify that no small leaks are present.
- Increasing ventilation is one of the most accessible and important actions to reduce sources of indoor pollution. Opening windows and turning on a vent that exhausts to the outside when cooking are simple steps that can lower the risk of indoor exposure.
- If you smell gas, exit the building and then immediately call your gas company to assess whether there is a leak in or nearby your home.
“Home is Where the Pipeline Ends: Characterization of Volatile Organic Compounds Present in Natural Gas at the Point of the Residential End User” by Drew R. Michanowicz, Archana Dayalu, Curtis L. Nordgaard, Jonathan J. Buonocore, Molly W. Fairchild, Robert Ackley, Jessica E. Schiff, Abbie Liu, Nathan G. Phillips, Audrey Schulman, Zeyneb Magavi, and John D. Spengler, https://doi.org/10.1021/acs.est.1c08298