5-EPA
 www.epa.gov/nhsrc
technical  BR
          Provisional Advisory Levels (PALs) for Hazardous Agents
      Provisional Advisory Levels support risk-based decision making

      There is concern that hazardous substances released
      during a terrorist attack will contaminate people and the
      environment, but there are few health-based guidelines
      for temporary building or outdoor site re-entry or for
      resumed use of water resources, as might be needed
      after a large-scale disaster. To address these exposure
      knowledge gaps, EPA is researching health-based
      provisional advisory levels (PALs) for high priority
      hazardous chemicals and chemical warfare agents in air
      and drinking water.

      PALs are a tiered set of exposure values used to inform
      risk-based decision making during a response to
      environmental contamination involving hazardous
      chemicals. They are advisory levels for exposure to
      chemicals by the general public (including susceptible
      and sensitive sub-populations) and are developed for the
      following exposures to contaminated air and water:

      •  Acute (24 hours)
                                  As part of USEPA's Office of Research and
                                  Development, the National Homeland Security
                                  Research Center (NHSRC) provides products and
                                  expertise to improve our nation's ability to
                                  respond to environmental contamination caused
                                  by terrorist attacks on our nation's water
                                  infrastructure, buildings and outdoor areas.

                                  NHSRC conducts research related to

                                     • Detecting and containing contamination
                                        from chemical, biological, and
                                        radiological agents
                                     • Assessing and mitigating exposure to
                                        contamination
                                     • Understanding the health effects of
                                        contamination
                                     • Developing risk-based exposure
                                        advisories
                                     • Decontaminating and disposing of
                                        contaminated materials.
      •  Short-term (longer than one to 30 days)
      •  Long-term (longer than 30 days to two years)

      PAL Development Process
      The three health effect levels for defined exposure durations are PAL 1 (mild, transient, reversible
      effect), PAL 2 (serious, possibly irreversible effect), and PAL 3 (severe effect or lethality). The process
      for developing a PAL consists of the following steps:
      •  Identify chemicals of interest and evaluate their environmental fate and persistence
         Conduct a comprehensive
         literature search of published
         and unpublished toxicity data
         Assess toxicokinetic data to
         identify target organs/systems
         and toxicodynamic information
         Identify key studies (including
         supporting studies) along with
         their critical effects and point of
         departure values
         Calculate air and water
         concentrations that correspond
         to adult and child target effect
         levels
                 Characteristics of PAL Severity Levels
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Tier Levels
                  PAL 3 - - -A
                  PAL 2
                  PAL1
                                      Effect thresholds
                    severe effects, lethality
                    impaired ability to escape
                    increased severity of irreversible
                    serious long-lasting effects
                    mild, transient, reversible effects,
                    including changes from baseline
                    biomakers of exposure

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   Identify key uncertainties associated with toxicity information in order to apply appropriate
   uncertainty and modifying factors
The following are selected chemicals for which PALs have been determined:
Acrolein
Acrylonitrile
Aldicarb
Ammonia
Arsine
Boron trifluoride
Carbonyl difluoride
Chlorfenvinphos
Chloropicrin
Chlorpyrifos
Cyanide
Diborane
Dicrotophos
Dimethyl phosphite
Fluoroacetate salts
Hydrazine
Hydrogen bromide
Hydrogen chloride
Hydrogen selenide
Hydrogen sulfide
Isopropyl methylphosphonic acid
Methylphosphonic acid
Lewisite
Malathion
Dimethyl phosphite
Methomyl
Methyl isocyanate
Methyl paraoxon
Methyl parathion
Mevinphos
Oxamyl
Phencyclidine
Phosgene
Phosgene oxime
Red phosphorus
Tetrafluoroethylene
Titanium tetrachloride
Trimethyl phosphite

PALs Scientific Workgroup

EPA has established a scientific workgroup to provide a comprehensive review of data for the
derivation of the PAL values and the rationale for their derivation. The workgroup, which includes
scientists in academia, federal and state agencies, industry, and the private sector, meets quarterly to
evaluate and approve developed PALs.

Availability of PALs
Intended users of PAL values include EPA emergency planners and responders, risk assessors, and
on-scene coordinators. In order to obtain more information on PAL values,  please contact Kathy
Nickel (513) 569-7955 (Nickel.Kathv@epa.gov) or Femi Adeshina (202) 564-1539
(Adeshina.Femi@epa.gov). Additional risk information is also available at the NHSRC Web site
(www.epa.gov/nhsrc).


Principal Investigator: Femi Adeshina
Feedback/Questions: Kathy Nickel (513) 569-7955
December 2008
EPA/600/S-06/015A

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