Apr 11, 2024 - News

California leads U.S. emissions of a largely undetected greenhouse gas

Illustration of a skyline showing a nuclear plant on a waterfront with emissions from the towers only visible in the water's reflection.

Illustration: Aïda Amer/Axios

Southern California emits the nation's highest concentration of emissions of sulfuryl fluoride, a potent greenhouse gas and pesticide for termites, a new study shows.

Why it matters: The state touts its greenhouse gas reduction policies, but this gas is not named in state or federal data despite having a relatively long atmospheric lifetime and a high climate-change potential.

  • Other greenhouse gases could be slipping under the radar, too, researchers say.

Between the lines: Scientists used air samples and atmospheric measurements to detect, measure and trace these emissions, which are missing from both the California and U.S. greenhouse gas emissions inventories.

  • The EPA tracks and reports emissions through those inventories, which inform policymakers on reduction strategies, goals and progress.
  • This study suggests those policymakers aren't getting the full picture from current calculations and methods.

What they're saying: Atmospheric measurements are key to developing accurate inventories and determining if reduction strategies are actually working, according to Jens Muhle, an atmospheric research scientist at UCSD Scripps Institution of Oceanography and co-author of the study.

  • Without them, "it's like trying to diet without ever stepping on the balance," Muhle told Axios.
  • "Maybe California is not really reducing the emissions to the degree they think," he said.

The big picture: California emits more sulfuryl fluoride than the rest of the U.S. combined — 60-85% nationally and up to 12% of the global total — with most of it coming from Los Angeles, Orange and San Diego counties, the study shows.

A building covered by a blue striped fumigation tent.
A building being fumigated with sulfuryl fluoride. Photo: Bill Oxford/Getty Images

Zoom in: Sulfuryl fluoride is an EPA-approved pesticide that's been used in California for decades to treat termites and other insect infestations in homes and for agricultural fumigation.

  • It's used at shipping ports and is one of the few treatments for drywood termites, "a common regional pest that can form colonies in high, hard-to-reach parts of wooden structures," according to UCSD.
  • The gas is pumped into airtight tents surrounding an infested building, and any excess is released into the atmosphere.
  • About 85% of the state's sulfuryl fluoride emissions comes from that structural fumigation process, per the study.

Threat level: The manmade gas lingers more than 40 years, trapping heat that contributes to climate change.

  • While average concentrations of sulfuryl fluoride in the atmosphere are low, humans have been emitting it for decades at a rate faster than it can break down naturally, according to UCSD.

The fine print: Johns Hopkins University and NOAA researchers were also co-authors on the study, which was published last week in Communications Earth & Environment, a scientific journal published by Nature Portfolio.

  • They shared the findings with the California Air Resources Board and the Bay Area Air Quality Management District.
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