A new study points out that fumigant pumped into tented houses to kill pests remains in atmosphere six to 10 times longer than previously thought, thus becoming a potent greenhouse gas.
The study was conducted by a research team led by Jens Muhle, an atmospheric chemist at Scripps Institution of Oceanography, UC (University of California) San Diego.
The team discovered that Sulfuryl fluoride (SO2F2), a gas commonly used to rid buildings of termites and other pests, is a greenhouse gas that remains in the atmosphere about 36 years, six to 10 times longer than previously thought.
The team found that the concentration of the gas rose at a rate of 4 to 6 percent per year between 1978 and 2007, to a global atmospheric abundance by the end of 2007 of about 1.5 parts per trillion.
Its actual emissions into the atmosphere over this period were about one third less than estimated from industrial production data.
"It's extremely important to have independent verification of emissions," said Muhle. "You can't have regulation without verification, and you can't have verification without measurements," he added.
Muhle said that he started detecting an unknown compound in air samples taken in early 2004 at the Scripps pier with a newly developed measurement instrument.
He identified the compound as SO2F2 and concluded that the large fluctuations seen at the pier were likely related to the fumigation of local buildings.
The team expanded the analysis to air samples routinely collected around the world at stations of the NASA-funded Advanced Global Atmospheric Gases Experiment (AGAGE) network and to old air samples archived in metal cylinders.
With the help of atmospheric computer models, the Scripps team and colleagues at the Massachusetts Institute of Technology (MIT) determined that the most important removal process of sulfuryl fluoride is dissolution into the ocean, where it is decomposed by chemical reactions.
NOAA researchers working with the Scripps team calculated that one kilogram of SO2F2 emitted into the atmosphere has a global warming potential approximately 4,800 times greater than one kilogram of carbon dioxide.
"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. "But with methyl bromide being phased out, industry had to find alternatives, so sulfuryl fluoride has evolved to fill the role," he added.
"Unfortunately, it turns out that sulfuryl fluoride is a greenhouse gas with a longer lifetime than previously assumed," said Muhle. "This has to be taken into account before large amounts are emitted into the atmosphere," he added.