United States
Environmental Protection
Agency
Solid Waste
and Emergency Response
(5306W)
EPA530-F-00-032
February 2001
www.epa.gov
erview of Risk Assessment and RCRA
Risk is a measure of the likelihood that damages or harm will
occur as a result of exposure to a hazard or a physical threat.
Whether a risk is significant depends on the context in
which the hazard occurs and the potential consequences.
Furthermore, the perception of risk might differ from one
person to the next depending on the nature of the risk. For example, risks
from chemical hazards are often viewed differently than other known or
easily recognized risks, such as driving a car or crossing the street. Risk
assessment is used by the U.S. Environmental Protection Agency (EPA) to
analyze the potential for adverse human health or ecological effects due to
the presence of toxic chemicals in the environment. Risks of concern to
EPAs hazardous waste program, such as ground water or soil contamina-
tion, might be unknown to the individuals or communities affected by
them and might not always be readily traced to a particular source or activ-
ity. In addition, EPA is concerned about risks that might occur in the future
and the need to take actions to prevent environmental contamination or
minimize the potential for exposure.
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How are Risks Assessed?
Risk assessment draws
upon technical and
scientific information
from a variety of dis-
ciplines, including
toxicology, epidemiology, and ecolo-
gy, as well as chemistry, physics,
and mathematics. Risk assessment
typically involves four major steps:
hazard identification, dose-response
assessment, exposure assessment,
and risk characterization. Hazard
identification refers to the scientific
data used and the weight of the evi-
dence gathered concerning the neg-
ative effects of a chemical agent or
environmental stressor. The dose-
response assessment (also referred
to as stressor-response relationships
in the context of ecological assess-
ments) attempts to quantify the
relationship between chemical/
hazardous exposure or dose and a
specific adverse effect in an organ-
ism, community, or ecosystem.
Exposure assessment deals with the
identification of potential exposure
pathways and exposed populations,
as well as the estimation of the dose
received by a particular receptor.
Exposures might occur as a result of
toxic chemicals being released from
landfills, incinerators, storage piles,
or other waste management units.
Exposure assessment generally
involves the use of fate and trans-
port models1 to predict the chemi-
cal concentrations expected and
might include the results of envi-
ronmental sampling and analysis.
All of the information is pulled
together in the risk characterization
report, where the major findings of
the assessment are described, and
the strengths, weaknesses, limita-
tions, and uncertainties are dis-
cussed.
Both quantitative and qualitative
measures are used to describe risk.
These risk measures may include
both the likelihood of the event
and the type and severity of an
adverse effect. They may include a
wide variety of effects ranging from
different kinds of cancers to repro-
ductive, developmental, or other
systemic toxic effects. Risks to the
general population, to individuals
residing in a given locale or belong-
ing to a particular subpopulation
(such as risks to children, the
elderly, or other susceptible popu-
lations), or risks to specific socio-
economic groups are often a
concern.
What is Risk Management?
Traditionally risk
assessment is distin-
guished from risk
management in that
risk assessment
attempts to answer the questions,
"Is there a risk from exposure to a
chemical substance? What do we
know about the risk? Who is most
affected by it?" In contrast, risk
management addresses questions
such as, "Should we be concerned
about the risk? If so, what should
be done about it? How can we best
mitigate the risk?" In practice, risk
assessment is used to address ques-
tions raised by decision-makers on
issues of public concern and, for
this reason, risk assessment is gen-
erally an iterative process that
engages decision-makers and the
public at various points along the
way. Opportunities for public input
include notice and comment on
proposed rules or permitting
actions, public hearings or forums
1 Fate and transport models are mathematical models that simulate the behavior of contaminants in various environments to pre-
dict contaminant concentration and mobility.
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on specific issues or topics, and peer
reviews of scientific studies and techni-
cal reports.
Risk management is a decision process
that considers social, economic, and
legal factors. The results of the risk
assessment, together with information
on alternative waste management
approaches, are evaluated in an effort to
arrive at an action or response that is
appropriate given the nature of the haz-
ard and the magnitude of the risk. Risk
management must consider uncertainties
that are inherent in the risk assessment
process. Outcomes of risk assessment
and management may include public
education efforts, enforcement and com-
pliance activities, cleanup of contamina-
tion, changes in regulations, or new
regulatory initiatives.
Risk Assessment and RCRA
EPAs hazardous waste program was established under
the Resource Conservation and Recovery Act (RCRA).
Risk assessment is used in a variety of ways in the
RCRA program. Risk information is an essential factor
in determining which industrial wastes are judged to
be hazardous wastes and should therefore be managed under the
RCRA hazardous waste system. Risk assessment is also used in
developing waste management programs for nonhazardous wastes.
Risk information is used in targeting waste minimization efforts,
issuing operating permits, determining the need for cleanup
actions at permitted facilities, and setting cleanup goals. Risk
assessment is also used in cost-benefit analysis for major rules and
regulations and to chart strategic directions for the RCRA program.
The goal of all of these efforts is to avoid or minimize risks from
the generation and management of hazardous wastes.
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Key References
For More Information
Understanding Risk: Informing
Decisions in a Democratic Society,
National Research Council, National
Academy Press, Washington, DC,
1996.
Risk Assessment in the Federal
Government: Managing the Process,
National Research Council, National
Academy Press, Washington, DC,
1983.
Other Resources
RCRA: Reducing Risk from Waste,
U.S. Environmental Protection
Agency, Washington, DC, 1997.
EPA530-K-97-004
Guidance for Risk Characterization,
Science Policy Council,
U.S. Environmental Protection Agency,
Washington, DC, 1995.
U.S. Environmental Protection
Agency
www.epa.gov/epaoswer/osw/
index.htm
Office of Solid Waste
Economics, Methods, and Risk
Analysis Division (5307W)
1200 Pennsylvania Avenue, NW.
Washington, DC 20460
Phone: 703 308-8855
Fax: 703 308-0511
EPA's Science Policy Council (SPC)
www.epa.gov/ORD/spc/index.htm
The goal of the SPC is to help guide
EPA decision-makers in their use of
scientific and technical information.
The SPC works to implement and
ensure the success of initiatives rec-
ommended by external advisory bod-
ies such as the National Research
Council and the EPA Science Advisory
Board.
EPA's Risk Assessment Forum (RAF)
www.epa.gov/ncea/raf/index.html
The RAF is a standing committee of
senior EPA scientists that was estab-
lished to promote consensus across
EPA programs on difficult and contro-
versial risk assessment issues. The RAF
assembles risk assessment experts in
a formal process to study, discuss,
and report on issues from a scientific
perspective and to assist in the devel-
opment of guidance documents for
use by EPA program offices.
EPA's Integrated Risk Information
System (IRIS)
www.epa.gov/ngispgm3/iris/
index.html
IRIS is an electronic database contain-
ing information on toxicity bench-
marks and human health effects that
might result from exposure to chemi-
cal substances in the environment.
IRIS was initially developed for EPA
staff in response to a need for consis-
tent information on chemical sub-
stances for use in risk assessments,
decision-making, and regulatory
activities.
EPA's Superfund Risk Assessment site
www.epa.gov/superfund/
programs/risk/index.htm
EPA's Office of Emergency and
Remedial Response (a.k.a., Superfund)
offers a variety of tools and informa-
tion on risk assessment. Although
Superfund guidance (e.g., Risk
Assessment Guidance for Superfund
(RAGS)) is intended for use at haz-
ardous waste sites listed on the
National Priorities List (NPL), it is also
used as a technical resource by risk
assessors in the RCRA program.
Society for Risk Analysis (SRA)
www.sra.org/index.htm
SRA is a nongovernmental organiza-
tion that provides an open forum for
persons interested in risk analysis.
SRA defines risk analysis broadly to
include risk assessment, risk character-
ization, risk communication, risk man-
agement, and policies relating to risk.
SRA members are concerned with
risks to human health and the envi-
ronment from physical, chemical, and
biological agents and from a wide
variety of human activities and natural
events.
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