Millions of Americans rely on natural gas to power their appliances, but until now there has been very little information about the chemical makeup of the gas.
A new study finds that natural gas used in homes throughout the Greater Boston area contains different levels of volatile organic chemicals that are known to be toxic and linked to cancer. The research was done by the Center for Climate, Health, and the Global Environment.
Drew Michanowicz said that natural gas is a major source of methane that is driving climate change. Most people don't realize that when natural gas leaks in our homes it can contain air pollutants that can be harmful to our health.
The researchers did not evaluate human exposure to pollutants in the study. Researchers collected over 200 unburned natural gas samples between December and May of this year. Researchers found 21 of the chemical compounds that are designated as hazardous air pollutants. They found that a leak with 20 parts per million methane may not have enough odorant for people to detect it. The samples were taken from the territories of Eversource Gas, National Grid, and the former Columbia Gas.
There are key findings.
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.
Natural gas is used by appliances in close proximity to people, so even small amounts of air pollutants could affect indoor air quality. The outdoor air quality can be degraded by persistent outdoor gas leaks.
The study shows that hazardous chemicals can be found in our homes even when we don't use gas appliances. The same chemicals are likely to be found in leaking gas distribution systems in cities and up the supply chain. It is possible for policymakers and utilities to better educate consumers about how natural gas is distributed to homes and the potential health risks of leaking gas appliances and leaking gas pipes under streets.
There are actions that policymakers and individuals can take to reduce health risks from natural gas.
There are policy actions.
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).
There are individual actions.
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.
More information: Home is Where the Pipeline Ends: Characterization of Volatile Organic Compounds Present in Natural Gas at the Point of the Residential End User, Environmental Science & Technology (2022). DOI: 10.1021/acs.est.1c08298 Journal information: Environmental Science & Technology
