Bacillus Anthracis Spore Inactivation by Fumigant Decontamination

Abstract

In 2001, envelopes containing virulent Bacillus anthracis spores were placed into the U.S. mail, resulting in contamination of mail processing and distribution facilities and office buildings. These spore-contaminated facilities were subsequently decontaminated primarily by fumigation with hydrogen peroxide, chlorine dioxide, and formaldehyde. These highly-publicized incidents resulted in increased public awareness of the threat to human health posed by Bacillus anthracis, and increased interest in sampling, detection, and decontamination of indoor surfaces, rooms, and buildings.

Fumigants offer advantages over liquid application for decontaminating rooms or buildings due to the increased coverage of large surface areas and ease of cleanup. From 2001 to the present, however, no decontamination technology has been registered by the U.S. Environmental Protection Agency (EPA) for use against B. anthracis spores; rather, decontamination has been performed through the EPA's issuance of Crisis Exemptions.

Since 2001, research and testing efforts have assessed the efficacy and maturity of sporicidal fumigants as well as the maturity, chemical toxicity, material compatibility, and ventilation requirements of these technologies. Several studies have been published in the scientific literature regarding fumigant inactivation of Bacillus spores; however, most decontamination studies with fumigants have utilized surrogates for B. anthracis surrogates, which can be more resistant to a specific type of fumigant (e.g., Geobacillus stearothermophilus and vaporous hydrogen peroxide) than virulent B. anthracis. Therefore, the purpose of this review is to summarize current knowledge available in the open scientific literature describing the inactivation of virulent B. anthracis spores by various fumigating agents with respect to key operational variables that can affect fumigant decontamination efficacy, such as fumigant concentration, contact time, operational temperature, and relative humidity.