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Anthrax spore decontamination using paraformaldehyde

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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 paraformaldehyde?

Paraformaldehyde is a white, crystalline powder with the odor of formaldehyde that has been used for more than 30 years to decontaminate laboratory facilities and to disinfect sickrooms, clothing, linen, and sickroom utensils. When heated, paraformaldehyde releases formaldehyde gas, which is the actual decontaminant.

Registration of pesticides containing paraformaldehyde

In 1964, under the authority of the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), paraformaldehyde was first registered as a sanitizer and fungicide for use on barber and beauty shop equipment. Since then, paraformaldehyde has been registered as a disinfectant, sanitizer, fungicide, and microbiocide. Sites for which this chemical was registered include household and domestic dwellings; ships and ship holds; bedding and clothing; and nonfood/nonfeed-transporting trucks.

Until 1991, paraformaldehyde was also registered for control decontamination of laboratories and experimental animal facilities. However, all registrations for this use and many of the other uses described above were canceled due to nonpayment of registration maintenance fees by the manufacturer.

Subsequently, only two products remain registered. Since the laboratory use of paraformaldehyde has not been registered since 1991 and no alternatives are available, EPA has also issued several quarantine exemptions (and usually renews them every three years) to continue this use for specific federal agencies:

  1. United States Department of Agriculture ( USDA) for use of paraformaldehyde in a poultry health laboratory in Arkansas;
  2. U.S. Army Medical Research Institute for Infectious Diseases (USAMRIID) for laboratory decontamination; and
  3. USDA to decontaminate high-containment microbiological laboratories at Plum Island, NY, and Ames, IA.

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, 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 the exemption, EPA would review the request and the supporting information and then determine whether the product could be used safely and effectively (i.e., cause "no unreasonable adverse effects").

If during this review any data were found to be deficient or missing, or any 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 would complete an application for a public health exemption, allowing the crisis exemption to continue in effect until the application was either withdrawn or EPA issued a public health exemption.

Crisis exemptions for paraformaldehyde

EPA first reviewed data related to the safety and effectiveness of using paraformaldehyde for inactivation of Bacillus anthracis spores in relation to a request by the U.S. Department of Justice (DOJ) to decontaminate a large mail sorting and stamping device located at its mailroom in Landover, MD. Available data indicated that paraformaldehyde 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 a crisis exemption for the limited sale, distribution, and use of paraformaldehyde to the DOJ on January 7, 2002. Upon review of the pertinent plans and data, EPA determined that paraformaldehyde would be safe and effective for use in a decontamination program that includes pre-sampling, treatment, and post-treatment sampling. The crisis exemption permitted the use of unregistered paraformaldehyde (manufactured by Hoechst-Celanese) containing a concentration of 95 percent paraformaldehyde (CAS #30525-89-4).

On February 14, 2002, EPA also issued a crisis exemption to allow the U.S. Department of State (DOS) to treat up to 200,000 diplomatic mail pouches with paraformaldehyde, subject similar conditions as the DOJ crisis exemption.

Use of paraformaldehyde for decontamination

For both the DOJ and DOS, all onsite work had to be performed by experienced personnel who were certified to perform hazardous materials decontamination work. After the areas to be fumigated were enclosed with a heavy duty plastic tenting structure, a powdered form of paraformaldehyde (pills) was heated, releasing the formaldehyde gas to decontaminate all surfaces in the enclosed spaces.

To ensure the safety of the applicators and those in the surrounding community, EPA approved specific guidelines regarding air monitoring and application procedures. The sites were set up so that contamination did not migrate outside of the work area. Physical barriers and security controls were established to ensure that only authorized personnel, with all necessary training and personal protective equipment, could access the site.

After fumigation was completed, authorized personnel conducted environmental sampling to determine whether any viable anthrax spores remained. All environmental samples were found to be negative for growth of Bacillus anthracis spores and thus the fumigations were determined to be successful.

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