Research Highlights

Using Hydrogen Peroxide to Decontaminate Indoor Surfaces

Representative view of test coupons inoculated with 100 Fl droplets containing approximately 1·0 times 10 to the power of 8 spores. (a) Image showing droplets immediately after application of spores. (b) Image of spores on test materials following overnight drying.

Bacterial endospores can survive in the environment for an extended time, and are resistant to a wide variety of treatments such as heat, desiccation, radiation, pressure, and chemicals. As potential bacterial spore decontaminants, ultraviolet light, γ-irradiation, wet/dry heat, ozone, aqueous solutions and mixtures, gels, and gases have been evaluated.

Gaseous forms of chlorine dioxide, ethylene oxide, formaldehyde, hydrogen peroxide, methylene bromide, ozone, peracetic acid, and propylene oxide have been used to inactivate Bacillus spores. These fumigating agents could be advantageous for large-scale decontamination of a room or building, as fumigants disperse easily and can potentially penetrate a large volume, thereby accessing all indoor surfaces. However, the toxicity, material compatibility, exposure time, concentration, and ventilation requirements vary among gaseous decontaminants. Considerations should be made for each of these treatments with respect to the intended decontamination application. Gaseous decontaminants may also yield better results than conventional surface cleaning with detergent sanitizers, as observed in a hospital environment decontaminated with hydrogen peroxide.

In aqueous or gaseous forms, hydrogen peroxide exhibits decontamination efficacy against bacterial spores, vegetative bacteria, viruses, amoeba, and prions. Hydrogen peroxide is considered less toxic than other fumigants such as chlorine dioxide, ethylene oxide, and formaldehyde, and breaks down into water and oxygen. Therefore, gaseous hydrogen peroxide has been used as a decontaminant for treating laboratory and medical equipment, pharmaceutical facilities, hospital rooms, and animal holding rooms.

In October 2001, the release of Bacillus anthracis (anthrax) spores from envelopes mailed in Trenton, NJ led to subsequent contamination of buildings including the mail processing and distribution centers in Washington, DC and Trenton, NJ, the Hart Senate Office Building, and numerous other mail-handling facilities. This contamination led to extensive remediation and clean-up efforts and increased public awareness regarding the possibility of future bioterrorism-related attacks. Since then, interest has grown in methods of detection, sampling, and decontamination of anthrax from surfaces, rooms, and buildings.

The purpose of the EPA study detailed in this report was twofold. First, researchers sought to develop and assess a laboratory-scale approach for evaluating decontamination efficacy of B. anthracis spores deposited on typical porous and nonporous indoor surface materials using commercially available technologies. Secondly, the researchers wanted to compare the decontamination efficacy of B. anthracis with selected surrogates.

The report describes the decontamination efficacies against spores of B. anthracis and two surrogates, B. subtilis and G. stearothermophilus, obtained during testing of a hydrogen peroxide gas generator. Bacillus anthracis, B. subtilis, and G. stearothermophilus spores were dried on seven types of indoor surfaces and exposed to ≥1000 parts per million hydrogen peroxide gas for 20 minutes. Hydrogen peroxide exposure significantly decreased viable B. anthracis, B. subtilis, and G. stearothermophilus spores on all test materials except G. stearothermophilus on industrial carpet.

Researchers observed significant differences in decontamination efficacy of hydrogen peroxide gas on porous and nonporous surfaces when comparing the mean log reduction in B. anthracis spores with B. subtilis and G. stearothermophilus spores. These results provide comparative information for the decontamination of B. anthracis spores with surrogates on indoor surfaces using hydrogen peroxide gas.

The report first appeared in the October 2005 Journal of Applied Microbiology, volume 99, issue 4, pages 739–748.

Contact: John Chang

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