Every day, millions of Americans depend on natural gas to power appliances such as ranges, furnaces and water heaters, but until now there has been very little data on the chemical makeup of the gas once it is used. it reaches consumers.
Natural gas used in homes in the Greater Boston area contains varying levels of volatile organic chemicals that, if leaked, are known to be toxic, linked to cancer and can form harmful secondary pollutants, new study finds for health such as particles and ozone. Research conducted by the Center for Climate, Health, and the Global Environment at Harvard TH Chan School of Public Health, PSE Healthy Energy, Atmospheric and Environmental Research (AER), Gas Safety Inc., Boston University, and Home Energy Efficiency Team ( HEET ) was published in Environmental science and technology.
“It is well established that natural gas is a major source of methane that drives climate change,” said Drew Michanowicz, Harvard Chan C-CHANGE Visiting Scholar and Principal Investigator at PSE Healthy Energy. “But most people haven’t really considered that our homes are where the pipeline ends and that when natural gas leaks, it can contain health-damaging air pollutants in addition to climate pollutants.”
The researchers conducted a hazard identification study, which assessed whether air pollutants are present in unburned natural gas, but did not assess human exposure to these pollutants. Between December 2019 and May 2021, researchers collected more than 200 samples of unburned natural gas from 69 unique cookstoves and construction pipelines in Greater Boston. From these samples, the researchers detected 296 unique chemical compounds, 21 of which are federally designated as hazardous air pollutants. They also measured the concentration of odorants in natural gas consumption – the chemicals that give gas its characteristic odor – and found that leaks containing around 20 parts per million methane may not have enough odorant to that people detect them. The samples were taken from the territories of Eversource Gas, National Grid and the former Columbia Gas, which together provide service to 93% of gas customers in Massachusetts.
- Consumer natural gas supplied to Massachusetts contains varying levels of at least 21 different hazardous air pollutants, as defined by the US EPA, including benzene, toluene, ethylbenzene, xylene and hexane.
- Concentrations of hazardous air pollutants in natural gas varied by location and time of year, with the highest concentrations observed in winter.
- Based on odorant concentrations, small leaks may be undetectable by odor – leaks up to 10 times natural levels may be undetectable, equivalent to a methane concentration of approximately 20 parts per million.
When gas leaks occur, even small amounts of hazardous air pollutants can impact indoor air quality because natural gas is used by appliances near people. Persistent outdoor gas leaks located throughout the distribution system can also degrade outdoor air quality as precursors to particulate matter and ozone.
“This study shows that gas appliances like stoves and ovens can be a source of dangerous chemicals in our homes even when we are not using them. These same chemicals are also likely to be present in the distribution systems gas leaks in cities and in the supply chain,” said Jonathan Buonocore, co-author and Harvard Chan C-CHANGE research scientist. “Policymakers and utilities can better educate consumers about how natural gas is distributed to homes and on the potential health risks of leaking gas appliances and leaking gas pipes under streets, and making alternatives more accessible.”
Researchers share steps policymakers and individuals can take to mitigate the 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 distinguishing between non-methane volatile organic compounds such as benzene and toluene.
- Gas utility providers could be required to regularly measure and report the odorant content of natural gas to customers, similar to the informational messages often produced by interstate gas pipeline companies.
- State regulations could require that direct measurement of unburned natural gas leakage into ambient air be included in emissions inventories and help to better determine public health risks.
- The Consumer Product Safety Commission has the power to set performance standards for gas ranges and ventilation hoods to limit emissions of air pollutants.
- Home inspectors and contractors may be required to perform leak detection surveys of natural gas appliances or measure methane in the ppm range, such as radon tests performed before a real estate transaction is completed. .
- Given the importance of odorants in detecting gas leaks, federal natural gas odorization regulations could be updated so that natural gas is odorized to achieve detection levels well below the current 1/5 of the lower explosive limit (detectable at approximately 1% methane).
- Since small leaks can escape our sense of smell, a home natural gas leak detection survey by a licensed plumber or heating, ventilation, and air conditioning (HVAC) contractor can verify that no small leaks are present. present.
- Increasing ventilation is one of the most accessible and important actions to reduce the sources of indoor pollution. Opening windows and opening a vent that exhausts to the outside when cooking are simple steps that can reduce the risk of indoor exposure.
- If you smell gas, get out of the building and immediately call your gas company to assess whether there is a leak in or near your home.
Source of the story:
Material provided by Harvard TH Chan School of Public Health. Note: Content may be edited for style and length.