UF Research: Methyl Bromide More Effective, Economical For Killing Anthrax

March 29, 2002

FORT LAUDERDALE, Fla.—As anthrax and other biological weapons continue to be worrisome threats, a University of Florida researcher has found a common pest control agent called methyl bromide is more effective and cheaper than current treatments in eradicating deadly bacterial spores from buildings.

“Tests indicate the fumigant – used for more than 50 years to control insect pests in buildings, grain elevators and fresh fruit – is a better option than current treatments such as chlorine dioxide for killing anthrax and other bacterial spores,” said Rudolf Scheffrahn, a professor of entomology with UF’s Institute of Food and Agricultural Sciences, who has studied pest control fumigants for more than 15 years.

Methyl bromide fumigation would have cost less than one-fourth of the estimated $23 million spent to clean up the anthrax contamination in the 3,000-square-foot Daschle Suite in the Hart Senate Office Building in Washington, D.C, according to Scheffrahn. The cleanup estimate is based on an Environmental Protection Agency study ordered by Sen. Charles Grassley, R-Iowa.

Earlier this week, officials with the U.S. Postal Service said using chlorine dioxide to clean up anthrax-contaminated postal facilities in Washington, D.C., and Trenton, N.J., would cost $35 million.

At an office building in Boca Raton, site of the nation’s first fatal anthrax infection in October 2001, methyl bromide would be the most effective treatment because the structure is so heavily contaminated with anthrax spores, Scheffrahn said. The building has been closed since October, but could be easily decontaminated with methyl bromide at a lower cost than current EPA cleanup methods, he said.

“Another advantage of using methyl bromide fumigant is that it will not damage equipment, furnishings or sensitive materials,” he said. “Chlorine dioxide is corrosive and may damage electronics, fabrics and photographs, among other things.”

Scheffrahn said emergency use of methyl bromide fumigant should not be affected by a looming 2005 phaseout of the gas. It is one of many gases that deplete the Earth’s protective ozone layer, and many uses will be eliminated after 2005.

“When national security is a stake, we need to have the option of using this highly effective and economical fumigant to kill bacterial spores in buildings,” he said. “According to EPA, the 2005 phase out will not affect at least three uses of methyl bromide, including quarantines, critical agricultural needs and emergencies.”

The new findings on methyl bromide are the result of research started in October 2001 by Scheffrahn and Mark Weinberg, general manager of Cobra Termite Control in Lauderhill. Knowing the gas commonly used for fumigating buildings against drywood termites was not effective against bacterial spores such as anthrax, they considered alternative fumigants.

“Methyl bromide gas was chosen for laboratory experiments because of its chemical properties, long track record in the pest control industry and its widespread agricultural use,” Scheffrahn said.

Following anthrax remediation guidelines developed by the U.S. Army and EPA, Scheffrahn and Weinberg conducted laboratory experiments on harmless spores of a related bacterium, Bacillus subtilis, which is even more resistant to chemicals than anthrax.

EPA granted Scheffrahn and Weinberg special permission to conduct tests using methyl bromide to kill the harmless spores that were planted in a vacant, fully furnished building at UF’s Fort Lauderdale Research and Education Center. Cobra Termite Control provided funds for the research.

Eighty paper strips, each containing as many as 100 million spores of the anthrax-like surrogate, were placed in walls, under carpets, inside computers and file cabinets, and in other hidden places that might harbor spores in an actual anthrax contamination.

“The tests killed the spores and proved that methyl bromide is more effective than chlorine dioxide gas as a building fumigant for anthrax,” Scheffrahn said. “Chlorine dioxide is an unstable gas and may not reach the desired target sites in buildings.”

Chlorine dioxide is the only structural fumigant that has been approved by EPA for anthrax decontamination, but agency officials will consider crisis exemptions for other chemicals such as methyl bromide on a case-by-case basis, said Jeff Kempter, senior adviser at EPA’s Office of Pesticide Programs in Arlington, Va.

“The safety and effectiveness of methyl bromide are the main considerations, and the UF research will help provide this information,” he said.

Weinberg, whose company fumigates more than 3,000 buildings a year in South Florida, said their system decontaminates the entire structure and uses existing fumigation methods. Scheffrahn and Weinberg have a patent pending on using methyl bromide fumigation to kill bacterial spores in buildings, and UF will retain rights to the technology.