&EPA
www.epa.gov/nhsrc
4
technical BR IEP
Provisional Advisory Levels (PALs) for Hazardous Agents
PALs are advisory risk values intended to aid
decision making during an emergency event.
Few health-based guidelines are available to inform decisions regarding the evacuation from or
reoccupation of buildings or sites, or the cessation and subsequent re-use of water resources,
following their contamination through the accidental or intentional release of toxic chemicals or
chemical warfare agents, or following a large-scale disaster. To address this need, EPA/ORD's
National Homeland Security Research Center (NHSRC) develops health-based Provisional Advisory
Levels (PALs) for high priority chemicals including toxic industrial chemicals and chemical warfare
agents, for both inhalation and oral exposures. Oral PALs are targeted to drinking water
ingestion, but are applicable to other oral exposures such as soil ingestion.
PALs are advisory levels for exposure to hazardous chemicals for defined durations of exposure:
•	24 Hours,
•	30 Days,
•	90 Days, and
•	Two years.
PALs Development
PAL1 values are developed for
mild, transient, reversible
effects; PAL 2 values address
serious, irreversible and/or
escape-impairing effects; and
PAL 3 values address lethality,
morbidity or life-threatening
effects. PAL values are
developed by typical noncancer
risk assessment methods by (a)
identifying priority chemicals;
(b) understanding their
environmental fate and persistence; (c) researching and summarizing their toxic effects, modes of
toxic action, and organ distribution in humans and test animals; (d) identifying key studies, sorting
their reported effects into PAL tiers and identifying the doses producing those effects; (e) adjusting
the doses to account for information gaps (uncertainty), and (f) presenting risk values as
concentrations of the chemical in air and water by accounting for body mass and the amount of
water ingested per day.
PAL-Based Decision Examples
PAL 3	
PAL 2	
PAL 1	
! Lethality, Morbidity,
I Life-threatening
|	effects
Irreversible or
t Escape-impairing
|	effects
| Reversible changes in
I biomarkers or
| baseline physiology
Adverse health effects
are not expected
Increasing chance of
fatalities
t/\
------------------—~
Increasing chance of
serious, irreversible
effects
Increasing chance of
discomfort, irritation
/\
Q)
L.
3
V)
O
a
x
LU
U.S. Environmental Protection Agency
Office of Research and Development, Homeland Security Research Program
EPA 600/S-17/044
February, 2017

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PALs have been determined for several chemicals, including:
Acrolein
Acrylonitrile
Aldicarb
Ammonia
Arsine
Boron trifluoride
Carbon disulfide
Carbonyl difluoride
Chlorfenvinphos
Chlorine
Chloropicrin
Chlorpyrifos
Cyanide
Diborane
Dimethyl phosphite
Fentanyl
Flouroacetate salts
G Nerve Agents
Hydrazine
Hydrogen bromide
Hydrogen chloride
Hydrogen selenide
Hydrogen sulfide
Methylphosphonic acid
Lewisite
Malathion
Methomyl
Methyl isocyanate
Methyl parathion
Mevinphos
Oxamyl
Phencyclidine
Phosgene
Sulfur mustard
Titanium tetrachloride
Trimethyl phosphite
PALs STEERING COMMITTEE
ORD/NHSRC has established a PALs Steering Committee comprising scientists and managers
from ORD, program offices and the regions. The committee meets approximately quarterly to
discuss issues related to user needs, emerging contaminants, risk methods and communication.
AVAILABILITY OF PALs
Intended users of PAL values include EPA emergency planners and responders, risk assessors,
and on-scene coordinators. For more information, please follow the "Assessing Exposure" link
under the "Characterizing Contamination and Assessing Exposure" section of our webpage:
http://www2.epa.gov/homeland-securitv-research
Technical Contact: John Lipscomb
EPA/ORD/NHSRC
lipscomb.iohn@epa.gov
513-569-7217
General Feedback/Questions: Kathy Nickel (nickel.kathv@epa.gov)
U.S. EPA's Homeland Security Research Program (HSRP) develops products based on scientific
research and technology evaluations. Our products and expertise are widely used in preventing,
preparing for, and recovering from public health and environmental emergencies that arise from
terrorist attacks or natural disasters. Our research and products address biological, radiological, or
chemical contaminants that could affect indoor areas, outdoor areas, or water infrastructure. HSRP
provides these products, technical assistance, and expertise to support EPA's roles and responsibilities
under the National Response Framework, statutory requirements, and Homeland Security Presidential
Directives.
U.S. Environmental Protection Agency
Office of Research and Development, Homeland Security Research Program
EPA/600/S-17/044
February 2017

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