(Beyond Pesticides, January 26, 2009) University of California at Irvine researchers have discovered that sulfuryl fluoride, an insecticide widely used to fumigate termite-infested homes and buildings, stays in the atmosphere at least 30-40 years and perhaps as long as 100 years and is about 4,000 times more efficient than carbon dioxide at trapping heat, though much less of it exists in the atmosphere. This raises concerns as levels have nearly doubled in just the last six years. Prior studies estimated its atmospheric lifetime at as low as five years, grossly underestimating the global warming potential.
“Sulfuryl fluoride has a long enough lifetime in the atmosphere that we cannot just close our eyes,” said Mads Sulbaek Andersen, a postdoctoral researcher in the Rowland-Blake laboratory and lead author of the study. “The level in the atmosphere is rising fast, and it doesn’t seem to disappear very quickly.”
Its climate impact in California each year equals that of carbon dioxide emitted from about one million vehicles. About 60 percent of the world’s sulfuryl fluoride use occurs in California. The insecticide is pumped into a tent that covers a termite-infested structure. When the tent is removed, the compound escapes into the atmosphere. Sulfuryl fluoride blocks a wavelength of heat that otherwise could easily escape the Earth, the scientists said. Carbon dioxide blocks a different wavelength, trapping heat near the surface.
“The only place where the planet is able to emit heat that escapes the atmosphere is in the region that sulfuryl fluoride blocks,” said Donald Blake, chemistry professor and co-author of the study. “If we put something with this blocking effect in that area, then we’re in trouble — and we are putting something in there.”
The chemists worry that emissions will increase as new uses are found for sulfuryl fluoride, especially given the ban of methyl bromide, an ozone-depleting pesticide regulated under the Montreal Protocol. Sulfuryl fluoride emissions are not regulated under the Montreal Protocol, though officials do consider it a toxic contaminant.
To measure sulfuryl fluoride’s atmospheric lifetime, the chemists put it inside a Pyrex chamber with compounds that are well understood in the atmosphere, such as ethane. They shined lamps on the chamber to simulate sunlight, which caused chemical reactions that eliminated the compounds from the air. By monitoring sulfuryl fluoride changes compared with changes to the well-known compounds, they were able to estimate its atmospheric lifetime.
“This is a cautionary paper,” said F. Sherwood Rowland, Donald Bren Research Professor of Chemistry and Earth System Science and co-author of the study. “It tells us that we need to be thinking globally – and acting locally.”
According to Beyond Pesticide research, sulfuryl fluoride is acutely moderately toxic by oral exposure (Toxicity Category II) and slightly toxic for acute inhalation (Toxicity Categories III and IV) and dermal vapor toxicity (Toxicity Category IV). Residents and workers are at risk for neurotoxic effects from acute exposure. Subchronic studies on rats have indicated effects on the nervous system, lungs, and brain. Developmental and reproductive effects have also been noted in relevant studies on rats. According to the National Research Council, fluorides might also increase the risk of developing Alzheimer’s disease, and boys exposed to fluoride in drinking water are five times more likely to develop osteosarcoma , a rare form of bone cancer. Since sulfuryl fluoride was only registered for use as a fumigant for existing infestations, EPA waived the environmental fate data requirements for reregistration in 1993 and did not consider ecological risks. The Agency expects that non-target organisms would not likely be exposed to sulfuryl fluoride and that the pesticide would not leach to groundwater or persist in the environment for any significant amount of time.
According to the most recent data by the California Department of Pesticide Regulations, sulfuryl fluoride is the top pesticide used in the state in 2007 for structural pest control and 14th for all pesticide application sites, with over 2.1 million pounds used in 2007 for structural pest control, over 3,200 pounds for landscape and rights-of-way applications, and about 42,000 on agricultural products such as almonds, broccoli, dried fruits, prunes, rice and other agricultural commodities.
Non- and least-toxic alternatives to using sulfuryl fluoride for structural pest management are viable and protect public health and the environment from hazardous chemical exposure. Ecologically-based land management systems and practices such as organic agriculture and organic lawns and landscapes also hold the key to freeing our country of its chemical dependency.
The study, “Atmospheric Chemistry of Sulfuryl Fluoride: Reaction with OH Radicals, Cl Atoms and O3, Atmospheric Lifetime, IR Spectrum, and Global Warming Potential,” appears in the January 21 online edition of the journal Environmental Science and Technology.