Home is Where the Pipeline Ends


Natural gas is used in over half of all buildings in the United States to power indoor appliances like kitchen stoves and water heaters. This places gas in homes and other buildings, where limited air flow gives even small leaks the potential to impact indoor air quality. Despite this proximity to people, very little data exists on the composition of natural gas when it reaches consumers. 

Home is Where the Pipeline Ends is the first study to provide a detailed analysis of the hazardous air pollutants present in natural gas used in homes. The study was published in Environmental Science & Technology and led by researchers at Harvard T.H. Chan School of Public Health, PSE Healthy Energy, Home Energy Efficiency Team (HEET), Atmospheric and Environmental Research (AER), Gas Safety Inc., and Boston University. 

Key Findings

  • Consumer-grade natural gas supplied to Massachusetts contains at least 21 different hazardous air pollutants, which are known to be toxic, linked to cancer, and can impact air quality at any point where gas is leaked.
  • Small leaks can be odorless, creating the opportunity for them to go undetected, particularly for populations suffering from a loss in the ability to smell due to age, chronic conditions, or infection (e.g., COVID-19).
  • Concentrations of hazardous air pollutants in natural gas are highly variable, with the highest concentrations observed in the winter. 
  • Hazardous air pollutants in natural gas leaks are not accounted for in any state or federal emissions inventories, making distribution-grade natural gas an untracked and unaccounted-for emissions source of hazardous air pollutants indoors and in urban areas. 


Based on the findings, researchers outlined several actions that policymakers and individuals can take immediately to help mitigate the potential health risks posed by distribution-grade natural gas. 

Policy Actions

  • Interstate gas pipeline companies could regularly measure and report more detailed information on the composition of natural gas, specifically differentiating non-methane volatile organic compounds such as benzene and toluene. 
  • Given the importance of odorants in gas to detect leaks, federal natural gas odorization regulations should 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). 
  • Local distribution companies should routinely measure and report natural gas odorant content to customers in a similar fashion to informational postings often produced by interstate gas pipeline companies.  
  • State regulations could require utility companies to report the volume of known gas leaks to better determine public health risk. 
  • Given that small leaks may not have a detectable smell, home inspectors and contractors could perform natural gas-appliance leak detection surveys with measurement instruments that detect in the ppm-range, similar to radon tests performed for real estate transactions. 
  • Natural gas is a previously uncharacterized source of these chemicals in indoor environments and one that could be potentially avoided with the electrification of appliances.
  • Building electrification programs must be pursued equitably—ensuring that environmental and social justice communities can benefit, rather than being left with polluting and increasingly expensive energy systems.

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.