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Anthrax spore decontamination using hydrogen peroxide vapor

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Current as of November 2012

Bleach, chlorine dioxide, ethylene oxide, hydrogen peroxide and peroxyacetic acid, methyl bromide, paraformaldehyde and vaporized hydrogen peroxide were pesticides used in federal decontamination responses to the bioterrorism attacks of October 2001. These attacks involved the intentional placement of Bacillus anthracis spores (the causative agent of the disease anthrax) into letters addressed to various locations on the East Coast of the United States. More information about biological threats.

This page describes the Agency’s actions with regard to the chemicals used in the anthrax spore decontamination activities. EPA temporarily approved these pesticides for sale, distribution, and use based on the remediation action plans submitted for each specific site and only in accordance with the requirements of each crisis exemption under Section 18 of FIFRA. These chemicals were not intended for use by the general public.

What is liquid hydrogen peroxide vapor?

Liquid hydrogen peroxide (H2O2) is an oxidizing agent used in industry for pulp, textile, and environmental applications. Industrial grade uses require concentrated solutions of 30 percent or greater.

Diluted liquid forms of hydrogen peroxide are common household products used as cleansers for cuts and scrapes, and are available in 3 percent to 10 percent solutions.

Vaporized hydrogen peroxide is registered by EPA as a sterilant that inactivates bacterial spores on environmental surfaces in an enclosed area. It is used in commercial, institutional and industrial settings to decontaminate or sterilize sealed enclosures such as isolators, workstations, and pass through rooms.

Responding to emergencies under FIFRA

Under Section 18 of FIFRA, the EPA "may exempt any Federal or State agency from any provision of this Act if the Administrator determines that emergency conditions exist which require such exemption."  To respond as rapidly as possible to the bioterrorism attacks, the Agency decided in 2001 to develop and issue the crisis exemptions itself. 

To obtain a crisis exemption from EPA for the unregistered use of a pesticide against anthrax spores, anyone who needed to use an antimicrobial product to inactivate Bacillus anthracis spores at contaminated sites had to submit:

  1. a written request to the Agency listing the antimicrobial product(s) to be used and describing how, when and where they would be used;
  2. data demonstrating efficacy of the product against bacillus spores; and
  3. remediation, sampling, and monitoring plans specific to the location of use.

Before issuing an exemption, EPA reviewed the request and the supporting information and then determined whether the product could be used safely and effectively (i.e., cause “no unreasonable adverse effects”).

If during this review data were found to be deficient or missing, or adverse human health or environmental concerns were identified, EPA could deny the exemption request.

If a crisis exemption was issued and EPA determined that use of the product would be needed beyond the 15 day use period, EPA completed an application for a public health exemption. This allowed the crisis exemption to continue in effect until the application was either withdrawn or EPA issued a public health exemption.

Crisis exemptions for liquid hydrogen peroxide vapor

EPA reviewed data related to the safety and effectiveness of using liquid hydrogen peroxide vapor for inactivation of Bacillus anthracis spores. Available data indicated that liquid hydrogen peroxide vapor would reduce bacterial spore populations under specific conditions including concentration, pH, and contact time. EPA determined that the product could be used safely and effectively, and that no unreasonable adverse effects would occur from the requested uses.

Subsequently, EPA issued two crisis exemptions for the limited sale, distribution, and use of registered liquid hydrogen peroxide vapor for use against anthrax spores.

Use of liquid hydrogen peroxide vapor for decontamination

Applications of the pesticide products under the crisis exemptions were limited to employees or contractors of the GSA and DOS at the specified locations and in accordance with all of the requirements of site-specific, EPA-approved remediation plans.

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