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Developing Advisory Levels to Guide Recovery Actions

EPA researchers are leading the development of health-based emergency exposure advisory levels to help inform and advise communities and emergency response professionals while they recover from a chemical incident or attack.

PAL Levels

Following the terrorist attacks of September 11, 2001, national security and emergency response personnel immediately turned their attention to the need to be better prepared for future emergencies, especially those that might involve the deliberate or accidental release of hazardous chemicals.

To support that effort, EPA homeland security researchers have developed an approach to identify and communicate health-based emergency reference levels—Provisional Advisory Levels (PAL)—on the health dangers associated with exposures to high-priority hazardous chemicals and warfare agents.  While a number of exposure limit reference values exist for some of the chemicals of concern, they do not address all of the exposure scenarios and durations in question to inform recovery operations. 

“While a number of exposure limit reference values exist for some of the chemicals of concern, they do not address all of the exposure scenarios and durations in question to inform recovery operations,” reports EPA researcher Dr. Femi Adeshina.  

In the event of a deliberate or accidental discharge of hazardous chemicals, PALs will provide emergency responders and managers with critical information to support site-specific decisions and actions, such as how to address the nature and extent of clean-up operations, and to inform decision-making to allow re-entry into an area, such as a contaminated office building, to claim personal possessions.

PALs are threshold inhalation and oral exposure levels for the general public, derived for four exposure durations: an assumed continuous 24-hour, 30-day, 90-day, and 2-year exposure duration. The levels are based on extensive reviews of available scientific data on each hazardous substance.

To date, EPA has developed PALs for about 100 priority chemical agents.  This translates to a total of about 2,400 PALs covering acute, short-term, and longer-term durations for potential ingestion and inhalation exposures.

For each exposure duration, three levels—PAL 1, PAL 2, and PAL 3—are developed as the data allow, to distinguish the degree of severity of toxic effects:

  • PAL 1: are exposure levels expected to cause mild, transient, reversible effects
  • PAL 2: are exposure levels expected to cause serious, possibly irreversible effects
  • PAL 3: are exposure levels expected to cause severe, possibly fatal effects.

The longer-term (up to two year) exposure values are developed to inform responders involved in cleanup operations and the public regarding re-entry decisions.

EPA researchers developed and initiated a process to derive PALs that incorporates extensive peer review and collaboration across EPA and with other government agencies. A scientific workgroup including scientists in academia, state and federal agencies, industry, and the private sector meets quarterly to approve developed PALs. The workgroup provides comprehensive review of data available to derive PAL values.

By engaging a community of stakeholders and partners, EPA researchers developed PALs as scientifically-sound advisories to inform emergency planners and responders, to help the nation prepare for and respond to chemical releases.

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