Human Health Risk Assessment
Marian Olsen
U.S. EPA – ERRD
October 13, 2011
Presentation Overview
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Conceptual Site Model
Defining Risk Assessment
Conceptual Site Model
Superfund Risk Assessment Process
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Data Evaluation / Hazard Identification
Dose Response
Exposure Assessment
Risk Characterization
• Risk Assessment and Risk Management
Why Risk Assessment?
• EPA conducts risk assessment to characterize the
risks of cancer and non-cancer health effects posed
by the site.
• Risk Assessments provide a framework to
understand the:
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Nature and magnitude of the risk
Adversity of the risk
Confidence or reliability in estimates
Areas of uncertainty
Evidence supporting the decision.
Conceptual Site Model
• Who is exposed?
• What is the exposure media (i.e., sediment,
fish, surface water, etc.)?
• What activities bring them into contact with
the River (i.e., fishing, wading, swimming,
etc.)?
• What is the frequency and duration of the
exposures (i.e., # of days and # of years)?
• What are the potential health effects from this
exposure?
Conceptual Site Model
Human and Ecological: Sources, Pathways, and Receptors
BASELINE RISK ASSESSMENT
1. Data Collection and Evaluation
What contaminants exist and are of potential
concern?
2. Exposure Assessment
How might a receptor be exposed on or off site?
3. Toxicity Assessment
At what level of exposure are adverse effects
likely to occur?
4. Risk Characterization
What are the risks and uncertainties?
BASELINE RISK ASSESSMENT
Toxicity
Assessment
Data
Collection
Risk
Characterization
Data
Evaluation
Exposure
Assessment
Toxicity Assessment
• Toxicity Studies
– Animal Studies/Human Studies of workers exposed to
high levels of contaminants, etc.
• Weight of Evidence – Cancer
• Non-cancer health effects
• Toxicity Values
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Cancer Slope Factor
Inhalation Unit Risk
Oral Reference dose
Inhalation Reference Concentration
CANCER RISKS – Cancer Slope Factor
Risks expressed as risk per unit dose or concentration
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Increasing Effect
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8
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Increasing Dose
Non-Cancer Hazard
THRESHOLD
Dose (mg/kg-day)
Sources of Toxicity Information
• Hierarchy of Toxicity Information
– Memo dated 12/2003 (OSWER Directive 9285.7-53)
• Integrated Risk Information System
• Provisional Peer Reviewed Toxicity Values
• Other Sources
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ATSDR
CalEPA
Health Effects Assessment Summary Tables
NJDEP
• Superfund Technical Support Center
U.S. EPA Superfund Risk Assessment
Exposure
Risk
Toxicity
• Evaluated under current (baseline) and future
conditions
• Baseline conditions evaluated in the absence of
institutional or other controls
• Goal is health protection under reasonable
maximum exposures
EXPOSURE ESTIMATES
Central Tendency Exposure
OBSERVATIONS
Reasonable Maximum
Exposure
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TOTAL
EXPOSURE
EXPOSURE FACTORS
Intake = C x IR x EF x ED
BW x AT
EXPOSURE FACTOR
VALUE
Concentration in Fish (C)
Sampling Results
Ingestion Rate (IR)
Meals/year
Exposure Frequency (EF)
365 days/year,
Exposure Duration (ED)
Years
Bodyweight (BW)
70 kgs (adult)
AT (averaging time)
(depends on whether a carcinogen or a
non-carcinogen)
Summary of Important Exposure
Factors
Exposure Factor
Central Estimate
Reasonable
Maximum (RME)
Part of 17 Mile
Study
Part of 17 Mile
Study
Fish Ingestion
Consumption (grams/day)
Exposure Duration (years)
Contaminants Lost in Cooking (%)
Exposure to Water/Sediment
Adult/Child Recreation (Summer)
Adolescent Recreation (Summer)
Residence Duration (years)
OW Hierarchy of Fish Ingestion Rates
• Four preference hierarchy (OW Methodology
for Water Quality Criteria)
– use of local data;
– use of data reflecting similar geography/
population groups;
– use of data from national surveys; and
– use of EPA’s default intake rates.
(From EPA Office of Water Methodology for Deriving Water Quality
Criteria for the Protection of Human Health (2000))
Cooking Loss
• Reasonable Maximum Exposure
– No Cooking Loss
• Central Tendency Exposure
– Evaluation of literature based values
• Dioxins
• PCBs
• Other contaminants
Other Parameters
• Residence Time
• Bodyweight - defaults
– 70 kgs for adult (18 years and older)
– 15 kgs for child (1 to 6 years of age)
• Lifespan
– 70 years
BASELINE RISK ASSESSMENT
Toxicity
Assessment
Data
Collection
Risk
Characterization
Data
Evaluation
Exposure
Assessment
RISK CHARACTERIZATION
STEPS
1. Review exposure and toxicity data
2. Quantify risks for individual and
multiple chemicals
3. Combine risks across exposure
pathways
4. Evaluate and present uncertainties
5. Summarize risk assessment results
EVALUATE UNCERTAINTY
CATEGORIES OF UNCERTAINTY
RISK ASSESSMENT
SELECTION
OF
SUBSTANCES
EXPOSURE
ASSESSMENT
Source: U.S. EPA 1989, pages 8-17
TOXICITY
VALUES
MULTIPLE
PATHWAY
SUMMATION
Risk Assessment and Risk Management
Risk Management
Risk Assessment
Dose Response
Assessment
Hazard
Identification
Exposure
Assessment
Statutory, legal
considerations
Politics
Risk
Characterization
Available
Technology
Social
Factors
Risk
Management
Options
Economics
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Resources
• Risk Portal – www.epa.gov/risk
• National Center for Environmental Assessment including the
guidelines and Exposure Factors Handbook:
– www.epa.gov/ncea
• IRIS: www.epa.gov/iris
• Staff paper on Principles and Practices:
http://www.epa.gov/OSA/ratf.htm
• Office of the Science Advisor: http://www.epa.gov/OSA/
• Superfund Guidance:
http://www.epa.gov/oswer/riskassessment/risk_superfund.ht
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