Risk Assessment Presentation

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Presented By:

Claire Marcussen

Senior Environmental

ConsultantJune 24, 2010

Use of Risk Assessment to

Support Cleanup at Superfund

Sites

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Overview*

• What is Risk Assessment?

• Uses

• Risk Assessment Process

• When are Risk Assessments Conducted?

• Determining when Cleanup/Controls are Needed

* Interject opinions on the Koppers Risk Assessment

and Feasibility Study

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What is Risk Assessment?

• A systematic approach to determine the human

health effect and environmental impacts associated

with actual or threatened releases:

– Chemicals

– Radionuclides

• A required component to support cleanup decisions

at Superfund sites

• Must follow regulatory protocols

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Uses

• To support cleanup decisions

• Identifies chemicals and media requiring cleanup

• Prioritizes areas for cleanup

• Allows owners/operators to make focused decisions

• Supports property transactions/due diligence

• Develop cleanup levels

• Aids in site re-use

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Types of Risk Assessments

• Deterministic (most common)

– Calculations straightforward; not resource intensive

– Use of point estimates to come up with a risk values

– Use of established default assumptions

– Easier to describe and communicate

• Probabilistic (uncommon)

– Much more complex approach

– Used when simpler methods do not clearly support need for action (so why did they use it??)

– Uses statistically derived distributions of exposure factors and toxicity values to calculate risks

– Provides more detailed understanding of variability of risks (i.e., identifies what factors impact risks most)

– Difficult to communicate in a transparent manner.

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Risk Assessment Process

Hazard IdentificationHazard Identification

Exposure AssessmentExposure Assessment Toxicity AssessmentToxicity Assessment

Risk CharacterizationRisk Characterization

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Hazard Identification

• Conceptual Site Model = Road map

– Describes the sources, release and transport pathways, human and ecological receptors

– Ensures risk evaluation is focused on the right issues

– Koppers: continue to discover new sources (drums?)

• Data Evaluation

– Identifies useable data

– Is data complete (e.g., data gaps?)

– Koppers: for years never sampled for dioxin (risk driver requiring more delineation)

• Chemical Screening Step

– Reduce list of chemicals to those likely to drive risks at site (focuses risk assessment)

Conceptual Site Model

Dust

Leaching to

Groundwater

Surface

soil

Groundwater

Discharge

Garden

Data Evaluation

• Ensure that relevant data are available:

– To evaluate current and future exposures (on/offsite)

– Direct contact to surface soils (e.g., current 0-6”; future

0-6 ft to address site rework)

– Inhalation exposure (e.g., dust concentrations or

modeled dust concentrations)

• Ensure analytical methods are adequate

– Sensitivity: Can detect levels below “safe” levels

– Complete: Include methods that can detect site-related

chemicals (e.g. PAHs, metals, dioxins)

Chemical Screening Step

• Standardized approach

• Compare maximum site concentration to a

conservative health-based screening value

– Florida’s Soil Cleanup Target Level (SCTL)

– EPA’s Regional Screening Level (RSL)

– Residential exposure assumptions

• 10-6 cancer risk level,

• Noncancer hazard of 0.1

• Contributions from Natural Background

• Koppers: used commercial screening levels!

Example Chemical Screening Step

YesNA0.015 mg/kg39 mg/kgPAHs

No34 mg/kg210 mg/kg100 mg/kgChromium

NA

170 mg/kg

14 mg/kg

Natural

Background

Yes4.5 ng/kg45 ng/kgDioxin

No150 mg/kg160 mg/kgCopper

Yes0.39 mg/kg25 mg/kgArsenic

COPC?Residential

Screening

Level

(RSL/SCTL)

MaximumChemical

NA = not applicable

Screening Levels versus Cleanup Levels

(Default Residential Level – Arsenic)

Site-specific

cleanup

goal/level

No further study

warranted

Response action

clearly

warranted

“Zero”

concentrationScreening

Level

Very high

concentrationResponse/

Cleanup level

0.39 mg/kg

(10-6 risk)

3.9 or 39 mg/kg

(10-5 - 10-4 risk)100 mg/kg

(2x10-3 risk)

14 mg/kg =

Background (3.5x10-5)

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Exposure Assessment

• Cornerstone - - “no exposure/contact = no risk”

• Components

– Identify Completed Exposure Pathways

– Estimate Exposure Concentrations

– Calculate Chemical Intake/Dose

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Exposure Pathways

• Completed Exposure Pathway

– Chemical source and chemical release(s)

– Receptor point

– Exposure route

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Exposure Point Concentration

• Daily concentration you are exposed to

• Must address current and future likely exposure

scenarios

– Future outdoor industrial worker (widespread exposure)

• Area-wide average exposure concentration

– Future commercial or residential development (localized

exposures)

• Source Area exposure concentrations

– Offsite residential/commercial areas (localized)

• Koppers diluted exposure concentrations assuming

all receptors are exposed to the entire site

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Exposure Point Concentration

• Exposure point concentration

– Maximum detection (for screening)

– Average concentration (most common for risk assess.)

– Area-weighting (not commonly used)

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

0.5 acre

XX

XX5 acres

X

X

X

X

X

X

X

X

X

X

X

Residential

Exposure

Areas

Commercial/Industrial

Exposure Areas

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Chemical Intake

• Amount of chemical that enters the body

– Behavioral factors: frequency and duration of exposure

– Physical factors: body weight, skin surface area,

ingestion/inhalation/dermal contact rates

– Biological factors: bioavailability, absorption

– Koppers RA: used nonstandard absorption factors which

lowers risk and HI; ignored future residential use

• Intake (mg/kg/day) = Csoil x Contact Rate x ED x EF

BW x AT

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Chemical Intake

• Default Exposure Assumptions*

6

350

0.2

2800

10

200

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Residential

Child

250350Exposure Frequency (days/yr)

3300 (2373)5700Skin Surface Area (cm)

17 (20)20Inhalation rate (m3/day)

2524Exposure Duration (years)

0.20.07Soil adherence factor

(mg/cm2)

50/100100Soil Ingestion rate (mg/day)

70 (71.5)70Body weight (kg)

Industrial/

Commercial

Residential

Adult

Exposure Factor

*Probabilistic risk assessment uses a range of values; Koppers evaluated recreational and

worker exposure and not future residential risk

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Toxicity Assessment

• Use EPA and FDEP approved toxicity values to evaluate cancer and noncancer health effects

• Rely on chronic (long- term) exposures over time– Chronic = Lower doses cause long-term health effects

– Acute = Higher doses cause short-term health effects

• Cleanup for chronic effects is more stringent and is protective of acute effects

• EPA and FDEP Toxicity values have undergone peer review

• Koppers: used nonstandard toxicity values in the PRA (tend to be much lower than standard values)

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Toxicity Assessment

• Noncancer = reference doses; chronic target organ effect

– Many different “safe” dose levels based on different organs

– Use lowest “safe” dose to ensure protection for all effects

• Cancer = cancer slope factors*

– Many slope factors based on different types of cancer

– Use the most stringent slope factor to cover all types

• Special cases

– Toxicity equivalency factors (TEFs)-- polycyclic aromatic

hydrocarbons (PAHs) and dioxins

* Carcinogens must also be evaluated for noncancer effects as well.

Toxicity Assessment

• Toxicity Equivalency: Some chemicals are

members of the same family and exhibit similar

toxicological effects; however, they differ in the

degree of toxicity

– Applies to PAHs and Dioxins

– TEF applied to adjust the measured concentrations of

individual PAHs and dioxins as a fraction of the toxicity

of benzo(a)pyrene for PAHs and 2378-TCDD for

dioxins.

– TEF x soil concentration =

toxicity equivalent concentration (TEQ)

Kopper’s Toxicity Assessment

• Deterministic used EPA established CSF value for dioxin

• PRA used a range of toxicity factors (lowers risk/HI)

• PRA ran a second dioxin risk calculation without the EPA

dioxin CSF reducing risk by factor of 60

• EPA has a noncancer RfD value for dioxin; Koppers did not

evaluate noncancer effects to dioxin.

5E-04

2E-03

Risk

Commercial

Residential

Receptor

Group

12892004.5 (72)

9200

Site-wide

Exposure

Weighted

Conc. (ppt)

1118 (850)

HIEPA Regional

Screening Levels

(ppt)*

(HI=1/Risk=1E-06)

* EPA May 2010 Regional Screening Level Table (value in parentheses

is noncancer based).

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Exposure ToxicityRisk

Risk Characterization

Evaluate two effects:

Cancer Risks versus Noncancer Hazards

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Carcinogenic Risk

• Carcinogens = cancer risk

• Cancer risk = cancer slope factor x dose

– Probability of an individual developing cancer over

a lifetime

– Expressed as 1 in one million, 0.000001, or 10-6

– Risks from each chemical are additive to arrive at a

total site risk for each exposure scenario

Risk chem1 + Risk chem2 + Risk chem3

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Why Use Risk Numbers to Identify

Problems?

• Superfund and State regulations require to clean up

sites to levels that do not contribute “significantly”

above the risk that occurs from all other causes of

cancer in the general population.

• American Cancer Society indicates that 1 in 2 men

and 1 and 3 women will develop some type of

cancer in their lifetime based on studies in the

general population*

* www.cancer.org/docroot/PRO/content/PRO_1_1_Cancer_Statistics_2009_Presentation.asp

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Why Use Risk Numbers?

• EPA Regulation requires managing site risk within a range

10-6 to 10-4

• FDEP manages site risk > 1 x 10-6 *

• General population risk is 5 x10-1 and 3 x10-1 for men and

women.

• Ideally we would like 0 risk but not realistic

• EPA/FDEP Goal ��do not let site risks contribute significantly

above general population risks

Higher riskLower risk

10-6 10-5 10-4

* Unless background is above cleanup level

FDEP Target

EPA Target

10-1

Noncancer Hazards

• Noncarcinogens = noncancer hazard quotient (HQ)

– Ratio of site chemical intake/safe dose

– mg/kg/day site = Hazard quotient (HQ)

mg/kg/day safe dose

– HQchem1+HQchem2+HQchem3 = total HI

– FDEP and EPA threshold = 1.0

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Summarizing Risks/HIs

• To prioritize what areas require cleanup at large sites, risks and HIs should be segregated by:

– Exposure Areas onsite and offsite

– Exposure population (residential, commercial, etc.)

• Should identify chemicals driving risk and hazards onsite and offsite– Chemicals contribution > 10-6 risk

– Chemicals contributing > 1 HI

• Koppers: did not break site down into smaller areas for risk assessment

– Assumed entire site was the exposure area

– They only segregated ditch area

Koppers Deterministic Risk/HIs Summary

Dioxin, arsenic, PAH9E-050.04Recreational Older

Child

Dioxin2E-050.02Utility Worker (0-6 ft)

Dioxin1E-050.3Construction Worker

(0-6 ft)

Dioxin, arsenic, PAH3E-04 (4E-05)0.09Indoor Worker

Dioxin, arsenic, PAH5E-04 (8E-05)0.2Outdoor Worker

Dioxin

Dioxin and arsenic

2E-05

4E-06

0.01

0.02

Onsite Trespasser-Soil

Onsite Trespasser-Ditch

Chemicals of

Concern

Risk*+HIScenario

*Residential onsite risks would be greater than the receptor risk with most

frequent exposure (e.g., worker risks); thus, site-wide residential risks would

>1E-04 which is above FDEP and EPA thresholds.

+Parentheses = PRA risk result

Koppers Risk/HIs Summary

• Koppers did not evaluate future residential, worker, or recreational risks to 0-6 feet soils – Typically done for sites expected to be redeveloped

– Exposure concentrations higher in 0-6 ft for arsenic, PAHs, and PCP; dioxin similar

– Risks/HIs will be slightly higher using 0-6 ft for these scenarios.

• Even without calculating residential risk, since worker risk unacceptable so would residential risks (e.g., higher frequency and longer duration)

• Subsurface soils concentrations are higher or the same, so surface soil risk conclusions would also apply to subsurface soil.

When Risk Assessments Occur

Feasibility Study

Remedial Design/

Implementation

Detailed

Analysis of

Alternatives

Remedial

Action

Objectives

Remedial

Investigation

(RI)

Baseline Risk

Assessment *

Refine

Preliminary

Cleanup goals

based on risk

and legal levels

Risk evaluation

of remedial

alternatives

Evaluate:

Residual risk

Demonstrate

attainment

5-year review

* Note that the baseline conditions have changed since the RI,

as the site is no longer an active industrial facility. Thus, a risk

assessment has been recently revisited and submitted again

with the FS. Needs careful review!

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When are Cleanup/Controls Needed?

• Cancer Risks > Threshold (varies EPA vs FDEP)

– Risk > 10-4 generally require cleanup or controls (EPA)

– Risk < 10-6 generally do not require cleanup (FDEP)

– Risk > 10-6 and <10-4 case-by-case basis (EPA and

FDEP)

• Case- by- Case (target 10-6, 10-5, or 10-4)

– Contribution from natural background or other sources

not related to the site

• FDEP and EPA will not cleanup below background

– Environmental Setting (industrial versus residential)

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When are Cleanup/Controls Needed?

• Noncancer HI > 1.0

– Thresholds are consistent across EPA and States

– Can be no action if background metals are higher than

noncancer-based screening level

• Uncertainties

– Risks are only as good as the data

– Importance of delineating contamination (lack of data

does not mean “no risk”)

Developing Cleanup Levels

• Typically conducted as part of the FS

– Considers background levels

• FDEP and EPA will not cleanup below background

• Arsenic frequently is cleaned up to background levels and not the 1E-06 level in Florida and other States

– Considers noncancer effects (e.g., make sure final cancer risk-based level is also protective of noncancer effects)

– Considers cumulative exposure to all site chemicals of concern

Developing Cleanup Levels

• Koppers FS did not calculate cleanup levels for surface soil COCs (dioxin, arsenic, PAHs, PCP)– Need risk or HI-based cleanup goals for remedies to

achieve; to know how much soil needs to be cleaned up

• Koppers Risk Assessment did not calculate risks to 0-6 ft soil for site-redevelopment (e.g., soils reworked for site re-use)– Exposure Concentrations are higher for arsenic,

pentachlorophenol and much higher for PAHs; dioxins similar to surface soil concentrations

– Risks for subsurface soils would also be unacceptable for the same scenarios as surface soil.

– Need health-based cleanup goals for subsurface soil

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Questions?

Education

Risk Assessment Presentation