New map shows health risks of methane super emitters

A new map combines methane emissions at oil and gas infrastructure with other air quality data, creating a picture of the health risks arising from pollution at fossil fuel infrastructure.

Natural gas is mostly methane, but not entirely. Gas also contains hazardous air pollutants such as benzene, toluene, ethylbenzene, and xylene, often referenced together as BTEX. Such chemical pollutants can pose reproductive, immunological, hematologic, nervous, and respiratory harms to people living nearby.

“Natural gas is not just methane. It is actually closer to a chemical soup,” Seth Shonkoff, executive director of PSE Healthy Energy, an independent scientific research institute based in Oakland, California, told reporters on a call. “We found those hazardous air pollutants in nearly every sample of natural gas that we studied.”

Researchers at PSE Healthy Energy just published the Methane Risk Map. They combined data from Carbon Mapper, a satellite that can detect plumes of methane, along with thousands of documents from specific upstream oil and gas facilities, such as when a gas production facility submits pollution data to regulators for an air permit. The researchers then used that data to model methane-linked hazardous air pollutants and show how that interacts with other variables, such as weather.

In other words, the Methane Risk Map depicts plumes of toxic pollutants wafting across communities, estimating how many people are at risk of exposure.

“While methane-sensing satellites are providing unprecedented visibility of the methane emissions problem, these technologies are blind to the air quality impacts and human health risks that these methane emissions cause,” Shonkoff said. The Methane Risk Map is a “game changer,” he added, noting that methane is not just a climate problem, but also an air quality and human health story.

“It’s the first and only tool to combine methane emissions, gas composition, and meteorological data in regulatory-grade air quality models to estimate and visualize the air quality impacts and human health risks of methane super emitters,” Shonkoff said.

In one notable example from September 2021, a gas production site in Adams County, Colorado emitted a plume of gas that contained benzene that drifted over three square miles, putting nearly 3,500 people at risk, including a day care and a school.

The exact chemical composition of a specific stream of gas varies depending on the source. However, the researchers created a database after reviewing over 8,000 analyses of natural gas sites across 11 gas-producing states. Benzene was detected in more than 99 percent of the samples.

“What this basically means is that if there is a methane super emitter event coming from upstream oil and gas infrastructure, it is most likely to pose a health risk,” said Kelsey Bilsback, a principal scientist at PSE Healthy Energy and principal investigator of the Methane Risk Map.

For now, the Methane Risk Map has identified over 1,300 emissions events that have potentially impacted roughly 126,000 people who live within a two-mile radius of at least one of those events.

Bilsback admitted that their data is “a vast undercount” of the total number of people at risk. The map will include more data as it comes online. The map focuses only on the upstream sector, but the researchers plan to add midstream and downstream data over time. 

One interesting finding was that the type of equipment was an important variable. For instance, liquid storage tanks contained 59 times higher average benzene concentrations than gas-specific infrastructure, such as a pipeline. In tanks, pressure can change significantly, such as when a lid is opened, which can lead to some liquid hydrocarbons converting into a gas and releasing hazardous pollutants into the air.

“If a tank hatch is left open, that might not be a high-pressure event like a well blowout. And so, methane emissions may be relatively low, but benzene emissions can be relatively high.”

That underscores the fact that people living and working close to production sites are most at risk, including industry workers. More than 17 million people live within one mile of an active oil or gas well.

A second peer-reviewed study published in conjunction with the map found that these pollutants pose short-term risks to public health.

Bilsback said that on average, the pollution plumes pose risks to populations as far as two miles away. In the sparsely populated expanses of the Permian basin, this may be less of a concern. But in Colorado and California, where neighbourhoods are often located adjacent to oil and gas wells, the risks are more acute.

The researchers said the findings illustrate the need for regulatory guardrails, such as greater required setback distances for oil and gas infrastructure. The map provides tools to civil society, policymakers, and regulators, arming them with the data and evidence needed to protect the public. The map allows users to toggle between various pollutants and adjust concentration levels. It even has a “download” button that spits out a report on specific pollution events — a user-friendly feature that would make it easy for community members to spread the word.

One limitation of the map is that the emissions events are backward looking, publishing data on a significant time lag. Also, Carbon Mapper’s detection is not around the clock and does not detect smaller emissions events. The researchers said the map will continue to be updated so that it becomes more informative and impactful.

“Pretty much every time scientists detect methane emissions from an oil and gas facility, hazardous air pollutants are silently emitted as well,” said Sebastian Rowland, a scientist at PSE Healthy Energy, one of the authors of a peer-reviewed paper that underpinned the map.

“For too long, these emissions have gone undetected—our tool brings visibility to these emissions and associated public health risks.”

(Writing by Nick Cunningham; editing by Sophie Davies)