Risk Assessment 1

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Don Clay

Back 1

Cumulative Carcinogenic Risk based on reasonable maximum exposure for current and future land use is less than 10e(-4), non-carcinogenic less than 1, action is not warranted unless there are adverse enviornmental impacts. If MCLs or non-zero MCLGs are exceeded, action warranted.

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ARAR

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Applicable or Relevant and Appropriate Requirements

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PCB

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PolyChlorinated Biphenyl

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COC

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Chemicals of Concern

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BRAC

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Base Realignment and Closure

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EBS

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Environmental Baseline Surveys

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RI

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Remedial Investigation -

Project scoping

Site characterization

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FS

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Feasibility Study -

Establishment of remedial action objectives

development and screening of alternatives

detailed analysis of alternatives

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COPC

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Chemicals of Potential Concern

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CERCLA

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Comprehensive Environmental Response, Compensation, and Liability Act of 1980

(Law)

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MCL

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Maximum Contaminaant Level

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NCP

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National Oil and Hazardous Substances Pollution Contingency Plan

(Regulation)

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RAGS (Part A)

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Risk Assessment Guidance for Superfund, Human Health Evaluation Manual:

Part of the human health evaluation, the baseline risk assessment (Part A) is an analysis of the potential adverse health effects (current or future) caused by hazardous substances releases from a site in the absence of any actions to control or mitigate these releases (assumption of no action)

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ATSDR

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Agency for Toxic Substances and Disease Registry

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RAGS Objectives

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Provide baseline risks

determine levels of chemicals that can remain

compare potential impacts of remedial alt

consistent method for evacuating and

documenting public health threats

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PRP

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Potentially Responsible Parties

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RPM

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Remedial Project Manager

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RI/FS Steps

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Baseline Risk Assessment

Refinement of preliminary remediation goals

Remedial alternatives risk evaluation

Characterizes the nature and extent of risks posed by uncontrolled hazardous waste sites and for developing and evaluating remedial options

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Project Scoping

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Conceptual model of site: sources of contamination, potential pathways of exposure, potential receptors

What data do we need?

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Site Characterization

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Collection and analysis of field data

development of baseline risk assessment for human health and environmental effects

treatability studies

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Baseline Risk Assessment

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Help determine whether additional response action is necessary

Modify preliminary remediation goals

Help support selection of the "no-action" remedial alternative

Document the magnitude of risk at a site, and the primary causes of that risk

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Risk Assessment Steps

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Data Collection and Evaluation

Exposure Assessment

Toxicity Assessment

Risk Characterization

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NPC Criteria

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1) Overall Protection of Human Health and the Environment

2) Compliance with applicable or relevant, and appropriate Requirements (ARAS)

3) Long-term effectiveness and permanence

4) Reduction of Toxicity, Mobility, or Volume through the use of treatment

5) Short-term effectiveness

6) Implementability

7) Cost

8) State Acceptance

9) Community Acceptance

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Baseline Risk Assessment Equation

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Risk = Concentration * [(IR*EF*ED)/(BW*AT)] * TF

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Data Collection

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Collect Existing Data

Address modeling parameter needs

Collect background data

Conduct Primary exposure assessment

Devise overall strategy for sampling

Examine QA/QC measures

ID special analytical needs

Take active role during work plan

development and data colleciton

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Purposeful Data Collection

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While the contamination may be of concern the sampling should not be purposefully conducted if it is meant to be defensible

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Data Collection vs Sampling

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Never use term data collection: instead use Sampling

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Sampling questions

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How many?

Where to sample?

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Data Evaluation

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Combined data available from site investigation

Evaluate Analytical Methods

Evaluate Quantitation Limits

Evaluate qualified and coded data

Evaluate Blanks

Evaluate tentatively identified compounds

Compare site data with backgrounds

Identify chemicals of potential concern

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Data Limits

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Sample Quantitation Limits (SQL) - Sample Specific

Contract Required Quantitation Limits (CRQL)-not sample specific

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Exposure Assessment

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Characterize physical setting

Identify potentially exposed populations

Identify potential exposure pathways

Estimate exposure concentrations

Estimate chemical intakes

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Site Conceptual Model

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CSM - all possible methods of exposure

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Calculating exposure point concentrations

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EPC

Direct soil, Groundwater, Sediment sampling: Calculate the 95% UCL

Model concentrations:

Fate and Transport modeling

Vapor Intrusion

Particulate emissions from soil

Surface water concentrations from Groundwater discharge

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Reasonable Maximum Exposure

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RME

RME combines upper-bound and mid-range exposure factors so that it is health protective and reasonable but not the worst case

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Toxicity Assessment

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Gathering quantitative and qualitative toxicity information for substances being evaluated

Identify exposure periods for which toxicity values are necessary

Determine toxicity values for non-carcinogenic effects

determine toxicity values for carcinogenic effects

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Two Classes of Toxicological Responses

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Non-carcinogenic: Systemic toxic effects in organs: Reference Dose (RfD, RfC) - will not produce any adverse effect

Carcinogenic: Tumor formation (Benign and malignant): Cancer Slope factor - potency of a chemical

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Risk Characterization

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Review outputs from toxicity and exposure assessments

Quantify risks from individual chemicals

Quantify risks from multiple chemicals

Combine risks across exposure pathways

Assess and present uncertainty

Consider site-specific human studies

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EPA Four Risk Estimates

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Current and Future:

Reasonable Maximum Exposed Individual (RME)

Central Tendency Exposure Individual (CTE)

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Default vs Site-Specific

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Part A encourages the use of site-specific data so that risks can be evaluated on a case-by-case basis

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Risk Management Decisions

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Are risks above EPA's Acceptable Level:

Yes: Remediate (1E-4 Cancer Risk and 1.0 Hazard Index)

No: "No Further Action"

Do Concentrations Exceed ARARs? (Clean Drinking Water Act)

Yes: Remediate (exceed MCL)

No: "No Further Action"

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Data Evaluation:

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9 steps:

1) Gather all data available from sire investigation and sort by medium

2) Evaluate the analytical methods used

3) Evaluate the quality of the data with respect to sample quantitation limits (SQL)

4) Evaluate the quality of the data with respect to qualifiers and codes

5) Evaluate the quality of the data with respect to blanks

6) Evaluate tentatively identified compounds

7) Compare potential site related contamination with background

8) Develop a set of data for sure in the risk assessment

9) If appropriate, further limit the number of chemicals to be carried through the risk assessment

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GC/MS

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Gas Chromatography and Mass Spectroscopy (Peaks = different Chemicals)

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Non-detects in data

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Use 1/2 the SQL as a proxy value when chemical may be present but below detection limits

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High non-detect data

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If Exposure Point Concentrations exceed Maximum detect value, eliminate the high non-detect data

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Data Qualifiers

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J = Value is estimated

B = Blank

U = Non-detect

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Laboratory Contaminants

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Common laboratory chemicals: Ten Times Rule:

Consider the chemical non-detect if the maximum concentration is less than 10 times the maximum blank concentration

Non-common laboratory chemicals: five times rule:

Consider the chemical non-detect if the concentration is less than 5 times the maximum blank concentration

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Common Laboratory chemicals

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Acetone

2 Butanone

Methylene Chloride

Toluene

Phthalate Esters

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EPA steps for reducing number of chemicals

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1) Eliminate Lab Chemicals

2) Eliminate infrequently detected chemicals

3) Eliminate Essential Nutrients

4) Eliminate Background chemicals

5) Eliminate chemicals that pose "De Minimis" risk (Trivial, minor)

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Infrequently detected chemicals

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Chemicals detected less than five percent may be eliminated (minimum samples needed = 20)

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Essential Elements

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Calcium, Phosphorus, Magnesium, Iron, Zinc, Iodine, Copper, Manganese, Flouride, Sodium, Chromium III, Potassium, Chloride

Need to use Upper Intake Level (UL) - highest daily dose not to be exceeded

Estimated Average Requirements (EARS) = 50% healthy individuals (not good)

Recommended Dietary Allowances (RDA) = protects 97.5% healthy individuals

Minimum Daily Requirement (MDR)

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Exposure Point Concentration

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EPC = 95% Confidence Limit on the Arithmetic mean (95UCL)

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Collecting Samples

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Purpose is to calculate the Exposure Points Concentrations (EPC) for each Chemical of Concern (COC) for each Exposure Pathway to precisely estimate chemical Dose and Human Health Risk

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Environmental Medium to sample

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Surficial Soil = 0-6" below surface

Subsurficial Soil = 6" - 10'

Sediments

Surface Water (Rivers, Lakes)

Ground Water (Maximum Contaminant Levels for chemicals and Vapor Intrusion)

Air

Biota (Fish, Game)

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How Many samples

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Three methods:

Pre-specific Variance

Pre-specific Margin of Error

Pre-specific Relative Error

Rule of Thumb: 20 samples for soil and sediment

5-10 for Groundwater

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Uncertainty vs Variability

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Site Variability:

Cannot be reduced by further sampling

Uncertainty:

Can be reduced by further sampling

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Where to take samples

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Purpose:

Define Nature and Extent of Contamination

Goal of Remedial Investigation (RI)

Estimate Human exposure to chemicals

Goal of Risk Assessment

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Samplings Approaches:

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Risk Assessment vs Hot spot:

Random vs Clustered

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Injection Equation

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Intake (mg/kg-day) = (CS*IR*CF*FI*EF*ED)/ (BW*AT)

CS = Chemical Concentration in Soil (mg/kg)

IR = Ingestion Rate (mg soil/day)

CF = Conversion Factor (10-6 kg/mg)

FI = Fraction Ingested

EF = Exposure Frequency (days/year)

ED = Exposure Duration (years)

BW = Body Weight (kg)

AT = Averaging Time (period over which exposure is averaged - days)

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FI

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Based on Area of Contamination

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OSHA

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Occupational Safety And Health Administration

Regulatory

Uses Permissible Exposure Limit (PELs) - based on 8 hour time weighted average (TWA)

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Parts Per Million

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ppm: 1 ppm = 1,000 ppb = 1,000,000 ppt

1 milligram/kilogram (mg/kg)

1 milligram/liter (mg/l)

1 microgram/gram (ug/g)

0.0001%

Analogies:

1 inch in 16 miles

1 minute in two years

1 second in 11.5 days

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Parts Per Billion

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ppb:

1 microgram/kilogram (ug/kg)

1 microgram/liter (ug/l)

1 nanogram/gram (ng/g)

Analogies:

1 sheet in a roll of toilet paper from NY to London

1 second in 32 years

1 pound/120 million gallons

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Parts Per Trillion

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ppt:

1 nanogram/kilogram (ng/kg)

1 nanogram/liter (ng/l)

1 picogram/gram (pg/g)

Analogies:

1 square inch in 250 square miles

1 second in nearly 32,000 yeasr