Whole-Structure Decontamination of Bacillus Spores by Methyl Bromide FumigationEPA Contract Number: 68D03056
Title: Whole-Structure Decontamination of Bacillus Spores by Methyl Bromide Fumigation
Investigators: Weinberg, Mark J.
Small Business: Cobra Termite Control
EPA Contact: Manager, SBIR Program
Project Period: October 1, 2003 through December 31, 2004
Project Amount: $218,284
RFA: Small Business Innovation Research (SBIR) - Phase II (2003) Recipients Lists
Research Category: Air Quality and Air Toxics , SBIR - Air Pollution , Small Business Innovation Research (SBIR)
Millions of structures in the United States have been fumigated for household pests. One procedure includes sealing the entire building under tarpaulins, followed by introduction of a fumigant as a true gas to impinge upon all components within the seal. Cobra Termite Control investigated the use of structural fumigation techniques to decontaminate buildings of microbial contaminants, such as bacterial spores, using methyl bromide (MB) as the fumigant.
Laboratory studies identified the concentration, exposure time, and temperature parameters needed for MB to kill the spores of Geobacillus stearothermophilus and Bacillus atrophaeus, both considered surrogate spores for B. anthracis. Paper strips containing 106 and 108 B. atrophaeus spores exposed to MB at selected concentrations and temperatures prevented their germination. These results supported the use of MB in a field fumigation to decontaminate a building.
A partially furnished 10,000-ft3 trailer was fumigated with MB after 86 bacterial spore strips and 10 petri dishes with spores were hidden inside. Of the 46 G. stearothermophilus 106 spore strips recovered after the fumigation, none germinated. Of the 40 B. atrophaeus 106 spore strips placed, 20 produced vegetative cells during incubation. No B. thuringiensis spores survived in any of the 10 petri dishes (2 x 107 spores/dish). No damage was detected among electronic, photographic, or other commodities that were fumigated. Contrary to previous results, in which spores of B. atrophaeus were killed, the high number of strips containing viable spores fumigated in the trailer suggested that spore clumping had occurred during the manufacture of this lot of strips. In a demonstration trial, a proprietary scrubbing liquor comprised of water, inorganic salts, and a phase-transfer catalyst removed 99.9 percent of the MB sampled from trailer airspace.
The Phase I research project already demonstrated that MB can be commercially applied to kill bacterial spores using current whole-structure fumigation technology for rapid field decontamination without collateral damage. This Phase II research project addresses two additional research components vital for successful and U.S. Environmental Protection Agency-approved structural decontamination of B. anthracis spores: (1) laboratory studies to identify the concentration, exposure time, and temperature parameters needed for MB to kill the actual target spores of B. anthracis; and (2) a full-scale field trial to determine the efficiency of the proprietary MB scrubbing method that previously was demonstrated.
Commercial use of this technology currently is limited to a few contaminated buildings in the United States, including one structure in Boca Raton, FL. It is hoped that no further need for this technology will arise. If a future bioterrorism event involving weaponized B. anthracis does occur, MB fumigation offers a whole-structure, rapid, and economical alternative to current methods using chlorine dioxide gas.