New research suggests the nationwide surge in the potent greenhouse gas sulfuryl fluoride is almost entirely due to termite fumigation in the Los Angeles area.
Sulfuryl fluoride is a common treatment for drywood termites, bedbugs, roaches, and other pests. Also known by the brand name Vikane, the gas was developed by the Dow Chemical Company in 1959.
Concentrations of sulfuryl fluoride have increased exponentially worldwide: in 1978 it was 0.3 parts per trillion. Today it is more than 2.5 parts per trillion.
Recent research has found that one hotspot in the United States – the greater Los Angeles area – has the highest emissions of sulfuryl fluoride. In the region, concentrations of sulfuryl fluoride at times exceeded 400 parts per trillion between 2015 and 2017, said Johns Hopkins University graduate student Dylan Gaeta. The second highest emissions came from the California Bay Area. The rest of the country releases hardly any emissions.
According to the state Department of Pesticide Regulation, the source of emissions in California is clear: Structural fumigation accounts for 99% of sulfuryl fluoride use.
The study analyzed the concentration of sulfuryl fluoride in the air between 2015 and 2017 as measured by NOAA’s Global Monitoring Laboratory. The agency’s scientists regularly collect air bottles across the country using airplanes, towers, and surface collectors. NOAA scientists in Boulder, Colorado then test the pistons for tiny traces of gas.
Gaeta and his collaborators used these measurements to estimate the nationwide rate of emissions. They fed a statistical model with sulfuryl fluoride concentration measurements at various sites along with other relevant data and asked the model to infer where the emissions were coming from.
Compared to other states, California has unusually high rates of sulfuryl fluoride emissions. Credit: Dylan Gaeta
Compared to other states, California has unusually high rates of sulfuryl fluoride emissions. Credit: Dylan Gaeta“We expected to see small patches of emission in at least some other parts of the country,” Gaeta said. “The fact that we see almost everything from California? That was the shocking part.”
However, NOAA’s surveillance network does not extend to Florida, and the state does not track the use of sulfuryl fluoride. “It’s possible that Florida also emits and then just doesn’t get recognized by the NOAA network,” Gaeta said. He presented the research that had not yet been reviewed at the AGU autumn meeting in 2021.
A surprising greenhouse gas
For years, the insecticide was considered relatively harmless in terms of global warming.
To use the substance, fumigators first cover a building with an airtight tent. You fill the building with gas and let it work. After that, the workers open the windows to ventilate the building and release the gas into the atmosphere, where it is believed to degrade relatively quickly.
Over 100 years, the gas has a global warming potential that is more than 4,000 times higher than that of carbon dioxide.
The method gained popularity after the Montreal Protocol phased out another common fumigant, methyl bromide, which was found to erode the ozone layer.
But research in 2008 and 2009 showed that sulfuryl fluoride has a relatively high global warming potential and lasts longer than originally thought. The gas has a global warming potential of more than 4,000 times that of carbon dioxide over a 100-year period and remains in the atmosphere for about 36 years.
“When something stays in the atmosphere that long, you can’t reduce the impact of climate overnight by simply shutting off emissions,” said Mads Sulbaek Andersen, an atmospheric chemist at California State University Northridge who has studied the gas’s properties not involved in the new research.
The California Air Resources Board (CARB) recently added the insecticide to its list of short-lived climate pollutants. It is the only state to track its use, with records going back to the 1990s. But the state’s progressive emissions targets don’t include sulfuryl fluoride because the rules were written before scientists knew it was a greenhouse gas.
“CARB staff continue to monitor the scientific literature to better understand greenhouse gas emissions and the effects of sulfuryl fluoride and other pesticides,” said Dave Clegern, CARB’s public information officer.
fumigation alternatives
If fumigation stopped, “almost all emissions from the US would disappear.”
You can rid your home of pests without fumigation, but other methods may not work as well, said urban pest researcher Andrew Sutherland of the University of California Agriculture and Natural Resources (UC ANR). Other techniques for controlling drywood termites, bed bugs, and wood-boring beetles include heat treatments and topical application of insecticides. Both require advanced surveillance, detection and demarcation methods, Sutherland said.
But when infestations are widespread, nothing can match sulfuryl fluoride’s “efficacy and economy,” Sutherland said.
Los Angeles County Integrated Pest Management Advisor Siavash Taravati of UC ANR said sulfuryl fluoride is useful when an infestation is inaccessible to technicians. “A ban would require pest controllers to switch to local treatment methods.”
The change could resonate around the world: Structure fumigation in North America was the world’s leading source of sulfuryl fluoride emissions in 2019, according to a recent paper from the Massachusetts Institute of Technology.
If California fumigations stopped, Gaeta said, “nearly all emissions from the US would disappear.”
— Jenessa Duncombe (@jrdscience), staff writer
