Natural gas has become an integral part of U.S. society, with nearly half of all households relying on it to heat their homes. But researchers have found a “disturbing inequality” when it comes to its safety — the more racially diverse or the poor an area is, the more often harmful gas leaks occur. 

In a new study published on Wednesday in Environmental Science and Technology, researchers analyzed gas pipeline leaks in 2015 in 13 U.S. cities: Birmingham, Alabama; Boston, Massachusetts; Burlington, Vermont; Chicago, Illinois; Dallas, Texas; Indianapolis, Indiana; Jacksonville, Florida; Long Island, New York; Los Angeles, California; Mesa, Arizona; Pittsburgh, Pennsylvania; Staten Island, New York; and Syracuse, New York. 

In these metro areas, researchers found a dramatic difference between the gas infrastructure. 

Indianapolis and Mesa, for example, had 0.01 leaks per square mile of pipeline, which is far below the average leak density of 0.36. Meanwhile, Boston and Staten Island had a significantly larger number of leaks – with 0.75 and 0.79 leak indications per mile, respectively. 

There are numerous factors at play that lead to this situation, researchers found. When looking across the leak density in all 13 metro areas, they found that leaks are more frequent in areas that have older median housing ages. 

“A 10-year increase in median housing age is associated with an estimated 10% increase in leak density,” researchers say in their paper. 

And when they broke down the data even further, they also found that leak density also dramatically increased when the percentage of people of color in that area also increases. By looking at census data, they determined that cities with predominantly populated with people of color have a 37% higher gas leak density than those with mostly white populations. 

It’s a similar situation when it comes to wealth. The higher the median household income of an area, the lower the number of gas leak problems. Of the cities studied, those with higher incomes had roughly 26% lower density of leaks. 

A partnered project between the Environmental Defense Fund and Google Earth Outreach supported their findings. 

Boston, one of the country’s oldest cities, has aging pipes that are prone to corrosion and leaks. From March to June 2013, EDF and Google Earth found an average of one leak for every mile of natural gas pipeline. 

All of this reveals a “disturbing inequality” when it comes to the quality of local infrastructure, researchers said. When there is a high leak density, or numerous leaks per mile of pipeline, it indicates that the pipeline infrastructure itself is degraded. Roughly 45% of the city’s pipes are made from cast iron or other corrosive materials, they said, and more than half the pipes are older than 50 years. 

During that same time frame, the partners found that Indianapolis had about one leak for every 200 miles monitored. That city has far less corrosive piping that makes up less than 1% of its distribution system. 

“The sizes of these effects vary in their magnitude and uncertainty across metro areas, but their existence points to an unequal distribution of [natural gas] infrastructure quality,” the paper states. “The results of our analyses suggest that the burdens associated with natural gas leaks resulting from degraded pipelines are not equally distributed across race or income and thus present an environmental injustice.”

And this injustice does not pass without causing harm. 

From 2010 to 2020, the U.S. Pipeline and Hazardous Materials Safety Administration recorded 256 “significant” natural gas incidents attributed to corrosion or equipment failure, incorrect operation or material failure, the study notes. Those incidents resulted in 13 fatalities and 161 in-patient hospitalizations, and cost $1.7 billion in property damage, emergency response and released gas. 

In 2020, the researchers estimated that there are over 650,000 natural gas distribution leaks at any given time in the U.S. 

When they do occur, the bill is often left to the community. Most utility rate structures, researchers said, pass the expense of gas lost from leaks to consumers, who also pay for infrastructure improvements. 

“Cumulatively, the burdens of poor infrastructure as indicated by natural gas leaks raise concerns on many levels, and this work adds documentation to the litany of injustices already faced by vulnerable populations,” researchers said. “In the case of the natural gas distribution infrastructure, we find that the burdens are not always immediately visible, but many small failures can cumulatively increase the risk to life, health, and property and the environment experienced by vulnerable populations.”