EPA Risk Assessment Practices
Evaluation
Kerry L. Dearfield, Ph.D.
Senior Scientist for Science Policy
Office of the Science Advisor
United States Environmental Protection Agency
Presented to MIT Air Quality Symposium on Air Toxics
August 4, 2004
Risk Assessment
Risk assessment is a process where
information is analyzed to determine
if an environmental hazard might
cause harm to exposed persons and
ecosystems.
Paraphrased from “Risk Assessment in the Federal
Government” (National Research Council, 1983)
What Is Risk?
Definition: Probability of harm
or loss
Risk = Hazard x Exposure
NRC Risk Assessment Paradigm
Risk Assessment
Dose-Response
Assessment
Hazard
Identification
Statutory and Legal
Considerations
Public Health
Considerations
Risk
Characterization
Exposure
Assessment
Regulatory
Decisions
Control
Social
Options
Factors
Economic
Factors
Risk Management
National Research Council, 1983
Environmental Risk Analysis
Risk Assessment
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Nature of effects
Potency of agent
Exposure
Population at risk
– Average risk
– High-end risk
– Sensitive groups
• Uncertainties of science
• Uncertainties of analysis
Identify, Describe, Measure
Risk Management
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Social importance of risk
De minimis or acceptable risk
Reduce/not reduce risk
Stringency of reduction
Economics
Priority of concern
Legislative mandates
Legal issues
Risk perception
Evaluate, Decide, Implement
Comments Submitted to OMB
• In early 2003, an OMB FR Notice (Feb
3, 2003; 68 FR 5492-5527) asked for
comments on Federal Agencies’ risk
assessment practices
• Comments submitted were forwarded
to EPA to consider
General Nature of Comments
• EPA is being criticized for its risk assessment
practices
• Generally, the nature of these criticisms are:
• EPA must not intermingle policy judgments within the
scientific assessment of risk
• Risk assessments should not rely on conservative (“worst
case”) assumptions that distort outcomes and yield
estimates that grossly overstate risk
• Risk assessments should acknowledge the presence of
considerable uncertainty
EPA Risk Assessment
Task Force
• EPA senior managers requested a Task Force
examine EPA risk assessment practices; effort
under Office of the Science Advisor auspices
and has broad Agency representation
• Collect and analyze criticisms of our risk
assessment practices
• Determine fact from fiction
• Reassess our intent
• Consult with some expert group(s) regarding our
practices
EPA Risk Assessment
Task Force (cont.)
• Task Force reviewed criticisms and
grouped them according to common
themes (e.g., conservatism, use of worstcase scenarios, susceptibility, uncertainty)
• Published Staff Paper in March 2004 (on
OSA web site)
• FR Notice: March 25, 2004 (FR 69: 15326
– 15328); closed June 23, 2004
Document as Staff Paper
• Document is an EPA Staff Paper
• Presents the perspectives of EPA risk assessors
on how they understand risk assessment is
conducted at the Agency
• Also presents staff recommendations for EPA and
interested stakeholders to consider for how EPA
can move forward to strengthen and improve its
risk assessment practices
• Staff paper as it stands does not represent EPA
policy
Staff Paper Opens Dialogue
• Most important, the Staff Paper will serve as
a vehicle for opening a broad dialogue
among EPA staff, EPA managers, and
external parties about the practice of risk
assessment at EPA
• Paper represents the first step in a multistep process; FR notice asks for comments
on what issues/practices we need to focus
on for refinement/improvement
Risk Assessment at EPA
• EPA conducts risk assessment in order to
provide the best possible scientific
characterization of the risk in question,
based on a scientifically sound, rigorous
analysis of available information and
knowledge.
• Risk assessment informs decision makers
about the science implications of the risk
in question.
EPA Risk Assessment Approach
• Confidence in our risk assessments is
critical.
• Approach is to use to fullest extent site- and
chemical-specific data relevant to the
decision needed.
• Without such information, we use defaults to
ensure we cover the uncertainty of the
remaining data or lack of data.
EPA Risk Assessment Approach
(cont.)
• The data and information we use in
developing risk assessments has inherent
uncertainty and variability.
• Due to the general uncertainty and variability
of the data, information, and methodologies
EPA assesses, we tend to take a more health
and environmentally protective stance to
ensure we do not underestimate risk.
Look At Issue for Air Toxics
• Exposure assumption: use of 70
year exposure for HAPS (the
“porch potato”)
HAPs Exposure Assessment:
Conservative Issue
Are they too conservative? Closer look at
“Porch Potato” example for air toxics:
• Clean Air Act – specifically identify risk
to individual most exposed (IME) as a
critical decision variable for Hazardous
Air Pollutants (HAPs)
• Agency Benzene action specifies
Agency consider risks for lifetime
exposure, e.g., 70 years (54 FR
38044, 1989)
“Porch Potato”
Risk Assessment Approach
1
• For screening purposes, usually use 70 years as
lifetime exposure; if not pass screen, perform more
refined assessment
• Refined assessment presents range of risk
estimates using a distribution of exposure periods
(which includes IME & 70 years) and models of
exposures where people actually live
• Risk assessment portrays what is known about the
range of plausible risks, even though there are
always limited data
“Porch Potato”
Risk Assessment Approach
2
• Also, need to take into account that people
are not stationary for 70 years, 24 hours/day,
seven days/week, i.e., they are generally
mobile
• Need to present differences in indoor
exposures vs. outdoor exposures
• Range of risk estimates try to account for
these variables, but cannot account for all
aspects
“Porch Potato”
Risk Assessment Approach
3
• It should be noted that many people spend a
majority of time at home – annual average
concentration at home is indicative of
exposure concentration
• Long-term average indoor and outdoor
concentrations are nearly equivalent for
many outdoor pollutants (although not all)
• People have been known to live in one
location for much of or their entire lives
“Porch Potato”
Risk Management
• Risk managers consider the range of risk
estimates presented and decide which is the
basis for acceptable risk
• When the decision is based on the 70 year
lifetime exposure, it is a policy choice based
on legal and policy constraints (usually
considering the IME and using the Benzene
action to support the 70 years exposure)
EPA Risk Assessment
Recommendations
1
• Encourage the development of the specific
data necessary to more accurately assess
potential risks, including mode of action data.
• When we don’t have the specific data, we
must continually look for opportunities to
increase our certainty and confidence in the
defaults and assumptions we use, i.e.,
encourage the derivation of more dataderived defaults.
EPA Risk Assessment
Recommendations
2
• Focus on better communication of the data,
assumptions and defaults used in our risk
assessments, including how we deal with
uncertainty.
• A major method to help address uncertainty
is use of probabilistic analysis. We use it
now for exposure, but we now need to
explore the feasibility of probabilistic analysis
for all phases of risk assessment.
EPA Risk Assessment
Recommendations
• Transparency in risk assessment and risk
management practices is crucial
• Continued use of planning and scoping before
and during a risk assessment – need this
dialogue between risk assessors and risk
managers
• Encourage work on a decision making
framework
3
Other Risk Assessment Concerns
• Cumulative effects on infants and children of
pesticide residues and other substances that
have a common mechanism of toxicity
• Need to address cumulative effects of
multiple stressors vs. single chemical risk
assessments
• Need to characterize risk to infants, children,
pregnant women, the elderly, or other
populations that are identified as likely to be
at greater risk
Reach Out Efforts
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Staff Paper placed on EPA web site
Formal notice and comment via the FR
Direct meetings with interested stakeholders
Workshops with EPA’s Science Advisory
Board (and other groups, e.g., BOSC, NAS)
on promising areas for further development
of risk assessment practices
• Symposia at professional societies
Reach Out Efforts (cont.)
• Society of Toxicology (SOT): proposal for a CCT
(Contemporary Concepts in Toxicology) workshop
on probabilistic approaches for all phases of risk
assessment.
• Society for Risk Analysis (SRA): proposal for a
symposium at annual meeting on issue of
compounding defaults (“conservatism”) in risk
assessment.
• Society of Environmental Toxicology and Chemistry
(SETAC): discuss the organism-level vs populationlevel assessment issue at annual meeting.
Office of the Science Advisor
Web Site
www.epa.gov/osa
Also contains SPC materials
The End
Thank you very much