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Anthrax

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Anthrax Menu

Hazard Recognition

Anthrax Risk Reduction
Matrix Zones

Green Zone: Workplaces where contamination with anthrax spores is unlikely.

This zone covers the vast majority of workplaces in the U.S. The discovery of anthrax spores in workplaces has been very limited since 2001. If your workplace falls into the Green Zone, it is unlikely that specific measures to protect against anthrax exposure are necessary.

Yellow Zone: Workplaces where contamination with anthrax spores is possible.

Examples of workplaces in the Yellow Zone may include:

  • Workplaces that handle bulk mail (especially, working near equipment such as high-speed processors/sorters that could aerosolize anthrax spores).
  • Workplaces that handle mail from other facilities with known contamination.
  • Workplaces in close proximity to other facilities with known contamination.
  • Workplaces that may be targets for bioterrorists/criminal acts.

Red Zone: Workplaces where contamination with anthrax spores is confirmed or is strongly suspected.

Red Zone guidance addresses two situations:

  • Workplaces where authorities have informed employers that contamination with anthrax spores has been confirmed or is strongly suspected, and
  • Sites where emergency response workers are engaged in emergency response to, and cleanup of, bioterrorist releases of anthrax spores.

Employer actions during and following an anthrax release or other contamination event may vary depending on the details of the incident. Employers should follow law enforcement and public health agencies’/officials’ instructions to convey accurate information to workers and implement appropriate protective actions.

Historically, Bacillus anthracis (BA), which causes anthrax disease (generally referred to as "anthrax"), was an occupational hazard most common in animal handling and related occupations. However, the possibility for accidental or intentional release of BA and ongoing laboratory research to increase preparedness for responding to and countering such releases means a wider variety of workers may be at risk of occupational exposure.

The first step for any employer in recognizing potential BA exposure hazards their workers may encounter is to perform a job hazard analysis. A job hazard analysis is a process that focuses on job tasks as a way to identify inherent hazards and implement controls to protect workers. See OSHA's Job Hazard Analysis web page for more detailed information on conducting a step-by-step hazard analysis. Conducting a job hazard analysis can help employers determine whether their workers may have:

  • Potential BA exposure associated with work tasks - Workers and employers who may be involved in emergency response and recovery operations or related activities during or following releases of BA or who otherwise have a particularly high risk of exposure due to certain job tasks (e.g., working with BA in laboratories or handling mail);

    or

  • Potential BA exposure similar to the general public - Workers and employers who may be exposed during releases of BA or other emergency scenarios but who do not have emergency response roles or do not otherwise have a particularly high risk of exposure. Exposures resulting from accidental or intentional releases of BA are explained further below. Even though such exposures happen at work, exposures not associated with specific work tasks as described above are likely to be similar to other affected members of the general public.

In the case of an intentional release resulting from a terrorist or other criminal act, discovery of increased risk of exposure to BA may occur from physical evidence (such as a suspicious package containing powder), epidemiological or medical observations (such as individual cases of anthrax or individuals with symptoms consistent with anthrax), or claims of responsibility for or threats of anthrax attacks.

Use the OSHA Anthrax Risk Reduction Matrix to help determine if there is a credible risk of anthrax exposure at a worksite(s) from an intentional release of BA spores. This matrix is intended to help employers understand how to assess the risk of exposure to anthrax spores in their workplaces and to make the necessary decisions to successfully protect their workers from this exposure. The level of risk in any particular workplace is based upon factors such as:

  • The likelihood of a workplace being a target for BA contamination;
  • The proximity of a workplace or workstation to areas known to be contaminated with anthrax spores;
  • The likelihood of the workplace receiving mail or other items from a contaminated facility;
  • Any information provided by law enforcement or public health officials about the workplace's risk of receiving contaminated items;
  • The amount of mail the workplace receives;
  • The type of workplace - for example, a post office, bulk mail center, or public or private mail room where cross-contamination might be possible;
  • The potential that workplace operations and tasks could result in exposure if contaminated mail is received;
  • The use of high speed mail handling equipment, or other processes that might aerosolize anthrax spores during processing; or

Any other information or analysis that would indicate the workplace might be contaminated with anthrax spores.

The matrix offers basic guidance and protective measures to help employers in determining appropriate precautions based on the likelihood of contamination with BA spores. OSHA categorizes worksites into three risk zones—green, yellow, and red—as described in the "Anthrax Risk Reduction Matrix Zones" figure.

OSHA's Biological Agents Emergency Preparedness and Response page addresses general guidelines for biological agent releases, including as part of bioterrorism events or other international acts.

In the event of an anthrax release: Sampling conducted by the employer (if qualified or with assistance from a qualified contractor) or appropriate public health authorities can help assess the extent and degree of contamination. Aside from federal, state, local, tribal, or territorial government agencies, most employers are unlikely to have sampling capabilities, and will need to rely on emergency responders for assistance. In these cases, isolating the contaminated area will prevent further spread of potentially infectious materials (e.g., BA spores).

Regardless of who is performing sampling activities, various factors must be considered when sampling for BA, including:

  • method of dispersion for the agent;
  • purpose of the sampling, such as to identify the agent, determine extent of contamination, or confirm decontamination;
  • environmental conditions;
  • persistence of the agent;
  • physical state of the agent;
  • area/volume to be sampled; and
  • laboratory protocols.

For employers with sampling capabilities, prior to conducting sampling, develop a general sampling plan that outlines sampling objectives. Address the following questions when creating the sampling plan:

  • What are the specific sampling objectives?
  • What is the sampling approach used to meet the objectives?
  • What are the analytical methods used to test for contamination?
  • How will samples be packed, handled, and transported?

Other factors to consider when evaluating methods to meet the sampling objectives include laboratory capability, collection efficiency of the method, number of samples and level of quantification required, and need for quantification, suitability of the sample-collection and analytical methods, cost effectiveness and efficiency of the sampling plan in meeting stated objectives and the utility of the sampling method to the owner and/or federal agency having jurisdiction over the project.

The table below summarizes specific sampling objectives applicable for a response to a bioterrorism/criminal act involving BA.

Sampling Objectives

Sampling Objective Description
Real-time Monitoring Determine, in real-time, whether a release of spores is occurring or has occurred in a facility. Use real-time instruments to detect biological agents during and following a release.
Preliminary Assessment of a Facility (Screening) Determine qualitatively whether spores are present. Used to obtain composite samples of large areas and air volumes to maximize the likelihood of finding contamination.
Identification of Spores in a Bulk Material Determine qualitatively if a bulk material, such as a powder in an envelope, contains BA spores. Use on-site analysis for preliminary assessment, but laboratory analysis provides confirmation.
Determination of Contamination Determine whether items are contaminated, including letters/packages and other vehicles used to transmit the BA spores. Typically, collect composite surface samples of large items and/or individual samples of small items.
Extent and Location of Contamination (Site Characterization) After positive identification of BA, further sampling is necessary to determine how far the contamination has spread. Perform sampling to determine qualitatively, and if possible, semi-quantitatively, the extent and magnitude of contamination.
Effectiveness of Decontamination (Process Verification Sampling) Determine if decontamination is effective in reducing spores to a safe level.
Post-Decontamination Sampling (Re-occupancy Verification Sampling) Conduct final post-decontamination inside and outside of the exclusion zone to verify that the originally contaminated environment is sufficiently clean to allow re-occupancy of the area without the use of personal protective equipment (PPE).
Special Re-occupancy Considerations There may be site-specific circumstances requiring consideration of additional sampling.

After identifying the sampling objectives, use these objectives to develop a logical approach and a schedule to carry out the sampling tasks.

The OSHA Technical Manual, Section 2, Chapter 3, Appendix C contains information on biological agent detection equipment useful for sampling and detection of BA.

The National Institute for Occupational Safety and Health (NIOSH) provides guidelines for environmental sampling for BA,including surface sampling procedures for BA spores, sample packaging guidance, evaluation of air sampling methodologies, and recovery efficiency and limit of detection from surface samples.

NIOSH also provides training instructions, including the videos below, for the collection of environmental BA spores, from nonporous surfaces using macrofoam swabs and cellulose sponges.

Screen capture of an Anthrax Training Video

CDC Anthrax Training

Screen capture of an Anthrax Training Video

CDC Anthrax Training

Anthrax Risk Reduction Matrix Zones

Green Zone: Workplaces where contamination with anthrax spores is unlikely.

This zone covers the vast majority of workplaces in the U.S. The discovery of anthrax spores in workplaces has been very limited since 2001. If your workplace falls into the Green Zone, it is unlikely that specific measures to protect against anthrax exposure are necessary.

Yellow Zone: Workplaces where contamination with anthrax spores is possible.

Examples of workplaces in the Yellow Zone may include:

  • Workplaces that handle bulk mail (especially, working near equipment such as high-speed processors/sorters that could aerosolize anthrax spores).
  • Workplaces that handle mail from other facilities with known contamination.
  • Workplaces in close proximity to other facilities with known contamination.
  • Workplaces that may be targets for bioterrorists/criminal acts.

Red Zone: Workplaces where contamination with anthrax spores is confirmed or is strongly suspected.

Red Zone guidance addresses two situations:

  • Workplaces where authorities have informed employers that contamination with anthrax spores has been confirmed or is strongly suspected, and
  • Sites where emergency response workers are engaged in emergency response to, and cleanup of, bioterrorist releases of anthrax spores.

Employer actions during and following an anthrax release or other contamination event may vary depending on the details of the incident. Employers should follow law enforcement and public health agencies’/officials’ instructions to convey accurate information to workers and implement appropriate protective actions.

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