Using Bleach to Destroy Anthrax and Other Microbes

Using Bleach to Destroy Anthrax and Other Microbes

The following fact sheet is part of a series relating to chemicals that may be used in Federal Anthrax decontamination efforts . EPA has approved these pesticides against anthrax only for use by authorized personnel according to the specific requirements of the applicable crisis exemption and approved decontamination plans. These chemicals are not intended for use by the general public.

What is Bleach?

Registered liquid bleach products contain sodium hypochlorite, a compound used as a cleaner and to kill bacteria, fungi, and viruses. Sodium hypochlorite was first registered (licensed) for use in the United States as an antimicrobial pesticide in 1957. The term "bleach" stems from the discovery in the late 1700's that chlorine gas in water "bleached" or "whitened" textiles.

Antimicrobial Pesticides

Antimicrobial pesticides are substances used to control harmful microorganisms including bacteria, viruses or fungi on inanimate objects and surfaces primarily in indoor environments. Types of antimicrobial products have traditionally included sanitizers, disinfectants, and sterilants.

  • A "sanitizer" is a substance that significantly reduces the bacterial population in the inanimate environment, but does not destroy or eliminate all bacteria or other microorganisms.

  • A "disinfectant" is a substance that destroys or eliminates a specific species of infectious or other public health microorganism, but not necessarily bacterial spores, in the inanimate environment.

  • A "sterilant" is a substance that destroys or eliminates all forms of microbial life in the inanimate environment, including all forms of vegetative bacteria, bacterial spores, fungi, fungal spores, and viruses.

EPA's Registration of Pesticides

Before a pesticide can be marketed and used in the United States, EPA must evaluate the pesticide to ensure that it meets Federal safety standards for human health and the environment. Such evaluation is particularly important for antimicrobial pesticides (disinfectants, sterilants, and sporicides) that are used to reduce or eliminate microbial contamination. Once EPA determines that a pesticide meets federal safety standards, the Agency grants a license or "registration" permitting its distribution, sale, and use according to approved label instructions.

Before EPA grants registration for a pesticide product, the Agency will review efficacy and safety data to ensure that, when used according to the specific instructions of the label, the product is effective and does not pose any unreasonable adverse effect on human health or the environment. The label provides specific safety precautions and use directions for handling or using the product. EPA has concluded that bleach products registered to date have met federal standards for environmental and human health safety.

Uses for Bleach

  • Sanitizer/Disinfectant - Because bleach is effective against a wide range of bacteria, fungi, and viruses, EPA has registered sodium hypochlorite for use in the sanitization and disinfection of household premises, food processing plants, and agricultural settings. Bleach is also used in animal facilities, hospitals, and human drinking water supplies.
  • Laundry Additive - Most commonly, bleach is known for its use as a laundry additive where it is an effective disinfecting and sanitizing agent for fabrics and/or laundry water.

FIFRA Section 18 Emergency Exemption

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." Normally, a federal or state agency would submit an application for a FIFRA exemption to EPA for review and approval. If the EPA approves the request, it would issue either a specific or a public health exemption, as appropriate. However, if the emergency is of such urgency that a federal or state agency does not have enough time to submit an application for exemption and wait for EPA's approval, then the federal or state agency may issue a crisis exemption, which is effective for 15 days. In order for the crisis exemption to be extended beyond 15 days, the federal or state agency must submit an application for exemption to EPA.

In order to handle all anthrax contamination cases as quickly as possible, the Agency has decided to issue all crisis exemptions itself. To obtain a crisis exemption from EPA for the unregistered use of a pesticide against anthrax, a State or Federal agency must submit a written request describing the antimicrobial product(s) to be used; how, when and where they will be used; the data demonstrating efficacy of the product for the intended purpose; and how human health and safety will be protected. Prior to issuing the exemption, EPA will perform a multi-disciplinary risk assessment of the requested use, relying on data that have been supplied for the pesticide.

If, during this review, EPA notes any adverse human health or environmental concerns, EPA may deny the exemption request. If, however, EPA believes that the proposed use of an antimicrobial product will be effective and will protect human health and the environment, EPA will issue a crisis exemption. Moreover, if EPA determines that use of the product is needed beyond the 15 day use period, EPA will complete an application for a public health exemption on behalf of the requesting entity, which allows the crisis exemption to continue in effect until it is either withdrawn or EPA issues a public health exemption.

Determination of Safety and Efficacy for Crisis Exemption for Bleach

EPA has reviewed data related to safety and effectiveness before allowing an emergency exemption for bleach to be used specifically for anthrax decontamination. Available published data suggest that bleach will reduce bacterial spore populations under specific conditions including concentration, pH, and contact time. The Agency has also evaluated the efficacy of bleach as a sporicide using the AOAC Sporicidal Activity Test (modified) in its laboratory. More information regarding the AOAC analytical methods are available on the Web at: www.epa.gov/oppad001/dis_tss_docs/dis-09.htm .

On the basis of this review, EPA recently issued a crisis exemption for the limited sale, distribution, and use of EPA registered bleach products for use against anthrax. EPA has determined that the public health threat posed by the anthrax incidents constitutes a public health emergency of such immediacy that normal processing and review of a conventional public health exemption under FIFRA is neither prudent nor practical. Under this crisis exemption, only registered bleach products may be sold or distributed to employees of EPA, other federal, state, or local government agencies, and the U.S. Postal Service for use in anthrax decontamination.

Emergency Use of Bleach in Anthrax Decontamination

Applications of the pesticide products under the crisis exemption shall be limited to specific buildings or treatment sites identified by EPA or other Federal, State, or local governmental authorities, or the United States Postal Service. Applications must be conducted in accordance with use instructions from Federal, State, or local emergency response personnel following a plan that includes the following steps:

  • Pre-sampling to determine the extent of spore contamination at specific locations;

  • Spot remediation of highly contaminated surfaces through HEPA filter vacuuming;

  • Gross surface decontamination with registered bleach products;

  • Post-treatment sampling to determine that the anthrax decontamination has been effective; and

  • Re-treatment with registered bleach products if viable spores are detected

These steps apply to facilities where the treated surfaces will be re-used or the facility will be re-occupied. These steps do not necessarily apply to wastes or debris intended for disposal.

Applying Bleach

Based on published information and the Agency's own recent testing, EPA believes that registered bleach can be used in a facility decontamination procedure that includes sampling, cleaning, treating, and re-sampling, followed by additional treatment if necessary. Facility decontamination using registered sodium hypochlorite must be followed by post-treatment environmental sampling to confirm that the treated areas are free from anthrax spores (e.g., showing no growth when samples are cultured in the laboratory). When bleach is to be applied in the context of a facility decontamination plan, the conditions of application must be followed as described below. These conditions do not necessarily apply to personal protective equipment and other debris that will be further treated offsite.

Conditions of application:

  • only hard surfaces may be treated;

  • a bleach solution close to but not above pH 7 (neutral) and 5,000 to 6,000 parts per million (ppm) will be prepared by mixing one part bleach (5.25%-6.00%) to one part white vinegar to eight parts water. Bleach and vinegar must not be combined together directly, rather some water must first be added to the bleach (e.g., two cups water to one cup of bleach), then vinegar (e.g., one cup), and then the rest of the water (e.g., six cups). The pH of the solution should be tested with a paper test strip; and

  • treated surfaces must remain in contact with the bleach solution for 60 minutes (repeated applications will be necessary to keep the surfaces wet).

The science of anthrax decontamination is rapidly evolving, and the prescribed procedures for applying bleach have changed based upon more recent laboratory testing conducted by EPA. Early decontamination efforts may not have been conducted under the specific conditions described above. However, successful decontamination should have been confirmed by environmental sampling to assure that no viable anthrax spores existed after treatment.

More Information on Antimicrobial Pesticides

If you have general questions about the federal pesticide program browse the Web site, or contact EPA's pesticides office: