A chemical commonly used to wipe out termites and other pests from buildings is a much more problematic greenhouse gas that scientists previously thought, a new study finds.
The gas, sulfuryl fluoride, became the go-to fumigant after methyl bromide was banned by the 1987 Montreal Protocol because of its because of its ozone-destroying chemistry.
"Such fumigants are very important for controlling pests in the agricultural and building sectors," said Ron Prinn, director of MIT’s Center for Global Change Science and a co-author on the new paper. But with methyl bromide being phased out, "industry had to find alternatives, so sulfuryl fluoride has evolved to fill the role," he said.
Until the new work, nobody knew exactly how long the gas would last in the atmosphere after it leaked out of buildings or grain silos where it was used to fumigate.
"Our analysis has shown that the lifetime is about 36 years, or eight times greater than previously thought," Prinn said. Most of the sulfuryl fluoride that leaves the atmosphere is absorbed by the ocean, he added.
So it would become "a greenhouse gas of some importance if the quantity of its use grows as people expect," Prinn said.
One kilogram of sulfuryl dioxide emitted into the atmosphere has a global warming potential approximately 4,800 times greater than one kilogram of carbon dioxide.
For now though, the gas is only present in the atmosphere in very small quantities of about 1.5 parts per trillion (meaning that every trillion air molecules, only one 1.5 are sulfuryl fluoride), though it is increasing by about 5 percent per year.
For comparison, the amount of sulfuryl fluoride released into the atmosphere is about 2,000 metric tons per year, far lower than the amount of carbon dioxide, which is about 30 billion metric tons per year.
Still, the newfound extended lifetime of the gas "has to be taken into account before large amounts are emitted into the atmosphere," said Jens Muehle, an atmospheric chemist at Scripps Institution of Oceanography, in La Jolla, Calif., and leader of the study.
Fortunately, "we’ve caught it very early in the game," with time to find other fumigation substitutes, Prinn said.
Detection of the gas was made with the NASA-funded Advanced Global Atmospheric Gases Experiment (AGAGE) network. The findings are detailed in the March 12 of the Journal of Geophysical Research.
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