‘Under the radar’ greenhouse gas seen mostly in Southern California

(CN) — With its grand plan to become carbon neutral by 2045, California is known for its aggressive stance on the environment and climate change. But it turns out that the state leads the country in emissions of a little-known greenhouse gas called sulfuryl fluoride.

Primarily used as a pesticide for killing dry wood termites, around 12% of all the sulfuryl fluoride in the world is used in California, with most of that being used in Southern California, according to a new researchers in a study published Wednesday in the journal Communications Earth & Environment.

Researchers note that houses in Southern California are routinely covered in massive, circus-like tents and sprayed with the pesticide, in order to kill dry wood termites, which nest inside the wood of houses.

Dylan Gaeta, a doctoral candidate at Johns Hopkins University and the paper's lead author, says California's sulfuryl fluoride emissions are roughly equivalent to between one and three million metric tons of carbon dioxide each year — or an extra half million or so gas cars on the road every year.

Sulfuryl fluoride was only discovered to be a greenhouse gas in 2009, and the synthetic chemical has not been added to the various lists of greenhouse gases that are tracked by agencies like the Environmental Protection Agency and the California Air Resources Board.

"For most greenhouse gases, California has been very intentional about how it’s going to reduce emissions,” said Gaeta. “This one has slipped under the radar.”

He added: "Without some form of intervention, sulfuryl fluoride is going to keep accumulating in our atmosphere."

Sulfuryl fluoride, the only structural fumigant approved for use in the U.S., gained popularity after countries around the world began to phase out fumigants and aerosols that were depleting the ozone layer, one of the top environmental causes of the 1980s and 1990s. The U.S. accounts for 17% of all sulfuryl fluoride emissions worldwide.

In past decades, sulfuryl fluoride was thought to linger in the atmosphere for only about five years. But researchers in a 2009 paper showed that it sticks around for about 40 years, which means that it traps heat, much like carbon dioxide.

“It really is a double-edged sword," said Gaeta's co-author Scot Miller, an assistant professor of environmental health at Johns Hopkins. "Sulfuryl fluoride is less harmful than the banned fumigants, but it also contributes to global warming.”

The National Oceanic and Atmospheric Administration began tracking the chemical in 2015. Since then, its levels in our atmosphere have risen steadily.

"In order to get to net-zero emissions, we need a complete inventory of what greenhouse gases are out there," said Gaeta.

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