Samantha Rose Hunt, 12th March 2009

Chicago (IL) - A team of international researchers have discovered that Sulfuryl fluoride, a gas typically utilized in the repellant and control of insects, actually has an impact on global warming and is most definitely considered a greenhouse gas. In fact, though most are familiar with carbon dioxide (CO2) the effect of Sulfuryl flouride on global warming is 4,800 times worse than CO2. Lucky for us, the gas has a maximum lifespan of 36 years, and is not currently produced in high quantities so its ill fated effects can be halted prior to the occurrence of devastating effects.

"We've caught it very early in the game," stated Prinn, the TEPCO Professor of Atmospheric Science in MIT's Department of Earth, Atmospheric and Planetary Sciences.

Sulfuryl fluoride (SO2F2) was originally developed by the Dow Chemical Company. The gas is commonly used by farmers for its ability to fumigate soil, treat termites, and control insects post harvest on items such a grains, fruit and nuts. Typically it is utilized in warm weather regions of both the southwestern and southeastern United States and also occasionally in Hawaii.

Currently, sulfuryl fluoride is marketed by three different manufacturers utilizing four different brand names. Vikane, (which has been available commercially since the early 1960's) and ProFume are marketed by Dow. Zythor is marketed by EnSystex of North Carolina, and has just recently been introduced as the use of the product is approved state by state on an individual basis. The most recent of all would be Drexel Chemical Company's Master Fume.

In a December 2008 report, the United States Department of Agriculture claimed to be assessing fumigation utilizing sulfuryl fluoride as a treatment to quarantine exotic wood boring insects found in logs and timber, so the wood could be sold commercially for greater value.

The gas has been introduced most recently to replace methyl bromide, a fumigant which is being phased out under the Montreal Protocol due to its global warming inducing effects. Methyl bromide has been utilized to control insects at locations which store grain, and also in intensive agriculture and arid lands where drip irrigation is utilized in combination with blanketing the land with plastic sheets for moisture retention.

"Such fumigants are very important for controlling pests in the agricultural and building sectors," stated Ron Prinn, director of MIT's Center for Global Change Science and a co-author of the new paper. However while phasing out methyl bromide, the "industry had to find alternatives, so sulfuryl fluoride has evolved to fill the role," he said. Prinn also states that "fumigation is a big industry, and it's absolutely needed to preserve our buildings and food supply."

Researchers at the Massachusetts Institute of Technology, the Scripps Institution of Oceanography, and a few other institutions will report their findings from the study conducted on the gas this month in the Journal of Geophysical Research.

The detection of sulfuryl fluoride was made possible via a global research program called Advanced Global Atmospheric Gases Experiment (AGAGE), which was sponsored by NASA. "In AGAGE, we don't just monitor the big greenhouse gases that everybody's heard of," stated Prinn. "This program is also designed to sniff out potential greenhouse and ozone-depleting gases before the industry gets very big."

The scientists measured the atmospheric concentration of sulfuryl fluoride, to determine the current emission levels and to additionally gauge what impact the gas could have on world climate. Currently the gas is present in the atmosphere in extremely small quantities of about 1.5 parts per trillion, however this number is increasing at a rate of nearly five percent each year (in 50 years it would increase to 16.4 parts per trillion, still well below CO2's current 385 parts per million average in Earth's atmosphere).

Prior to the study it had yet to be determined how long sulfuryl fluoride remained in the atmosphere after it had leaked from grain silos or buildings. Now, scientists are stating, "Our analysis has shown that the lifetime is about 36 years or eight times greater than previously thought, with the ocean being its dominant sink," Prinn said. Effectively it could become "a greenhouse gas of some importance if the quantity of its use grows as people expect." A 36 year lifespan, combined with studies of its infrared absorbing properties conducted by researchers from the National Oceanic and Atmospheric Administration would "indicate that, ton for ton, it is about 4,800 times more potent a heat-trapping gas than carbon dioxide," claimed Prinn.

"Unfortunately, it turns out that sulfuryl fluoride is a greenhouse gas with a longer lifetime than previously assumed," says Muhle. "This has to be taken into account before large amounts are emitted into the atmosphere."

The team's approach has been described by Prinn as "a new frontier for environmental science." They are working under a concept of prevention (rather than repair) by eliminating potential climate dangers as quickly as possible instead of waiting until the damaging gasses are produced both commercially and on large scales. This not only protects the environment, but also the economy, as detection and awareness post production of products such as these which negatively affect the ozone can cause a significant loss of both capital and jobs.

Prinn feels that through the identification of greenhouse risks from this compound, prior to the opening of multiple factories for its widespread commercial production, the industry would have time to find additional substitutes while implementation is relatively easy. "Given human inventiveness," said Prinn, "there are surely other alternatives out there."

The lead author of the research paper is Jens Muhle of Scripps, and besides Prinn, the co-authors include Jin Huang, a research scientist at MIT's Center for Global Change Science, Ray Weiss of Scripps, who co-directs AGAGE with Prinn, and eight others from Scripps, the University of Bristol in the United Kingdom and the Centre for Australian Weather and Climate Research.