Why Are Emissions Of This Greenhouse Gas So High? Blame SoCal's Termites

While the state of California has set aggressive greenhouse gas standards over the next decade, it's leading the nation in the emissions of one greenhouse gas: sulfuryl fluoride, which is commonly used in termite fumigations.

A new study led by Johns Hopkins University scientists found that California is responsible for between 60% and 85% of sulfuryl fluoride nationwide. The highest levels of sulfuryl fluoride in the study were observed in Southern California, especially in Los Angeles County and north Orange County.

While more widely known greenhouse gases like carbon dioxide and methane are more prevalent, sulfuryl fluoride stays in the atmosphere for much longer — about 36 years — which means it can warm the atmosphere about 7,000 times as much as a similar amount of carbon dioxide.

Sulfuryl fluoride is used across the state and in other parts of the country as a pesticide, but it's often used in severe termite infestations as well. If you've ever seen a big tent covering up a house in your neighborhood, it may have been because that structure was being fumigated with sulfuryl fluoride.

"There's a special type of termite that lives in California called the western drywood termite," study co-author Scot Miller said. "They can actually form colonies within the structure of the house, and so that means the only way to really effectively treat them is to put that giant circus tent around the house and fumigate it, presumably with sulfuryl fluoride."

Miller and the study's lead author Dylan Gaeta were able to trace the gas emissions to termite fumigations since California keeps detailed records of pesticide use in the state.

"It's going to be the big circus tents that are the big emitter of sulfuryl fluoride," Miller said.

Scientists have known about how other greenhouse gases like carbon dioxide contribute to global warming for decades. Sulfuryl fluoride, on the other hand, was only recently identified as a greenhouse gas about 15 years ago following a report from the Scripps Institution of Oceanography.

The new study drew on nationwide data from the National Oceanic and Atmospheric Administration, which started monitoring for sulfuryl fluoride nationwide in 2015. The air samples used in the study were collected between 2015 and 2019.

Sulfuryl fluoride came into common usage as a replacement for methyl bromide, a toxic, potentially carcinogenic pesticide that depletes the ozone layer. The EPA phased out the substance in 2005, leading agricultural producers and pest controllers to turn to alternatives.

At that point, the capacity of sulfuryl fluoride to act as a greenhouse gas wasn't widely understood, but the study's authors hope that this will change, especially as California aims to cut its greenhouse gas emissions in half within the next decade.

"At some point we're going to have to net zero emissions of greenhouse gas emissions," Gaeta said. "Just including sulfuryl fluoride in those greenhouse gas emissions inventories would give us some information. I think that's sort of like a baseline level."