Review Sheet #3
Environmental Risk Assessment:
Applications to Hazardous Waste Sites
EV-595 Fall 1997
Readings:
Calculated Risks
Chapter 2 - Exposures- All
Chapter 3 - Into the Body - pp. 25 to 31
Chapter 4 - Assessing Risks - All
Risk Assessment Guidance for Superfund
Chapter 1 - Introduction - All
Chapter 2 - Statutes, Regulations, Guidance and Studies Relevant to Human Health Evaluation - All
Chapter 6 - Exposure Assessment - All
Guidelines for Exposure Assessment (Supplemental Reading)
Federal Register; Vol. 57; No. 104; pp. 22888 - 22938 (May 29, 1992)
Exposure Assessment:
* Three step process - Interrelated
* Step 2 - Identify Exposure Pathways
- Exposure Pathway Analysis
- Links contaminant sources, locations, and environmental releases with population activities and locations.
- Results in determination of significant pathways of human exposure.
- Leads to construction of Conceptual Site Model.
- Four Parts of Exposure Pathway
1) Source \
2) Transport Mechanism \ All must be present to have a complete pathway.
3) Exposure Point / If one missing have incomplete pathway.
4) Exposure Route /
* ALL POSSIBLE PATHWAYS SHOULD BE EVALUATED, NOT ALL NEED BE QUANTIFIED *
- Source of Contamination and Mechanism of Release
- CERCLA documentation
- Records
- Types of Release Mechanisms - Types of Receiving Media
- Volatilization - Air
- Dust generation - Surface water
- Surface runoff - Ground water
- Overland flow - Soil
- Seepage - Sediment
- Leaching - Biota
- Tracking
- Uptake (biota)
- Fate and Transport
- Five Chemical Fates
- Transported - Not all transport is bad
- Physically transformed \
- Chemically transformed > Not all transformations are good
- Biologically transformed /
- Accumulated - Not all accumulation is bad
- Flow charts can be used to examine fate and transport
- Questions for fate and transport
- Where are the principal mechanisms for change or removal?
- How does the chemical behave in environmental media?
- Does the chemical react with other compounds? What are the products of the reaction?
- Is there intermediate transfer? What are the mechanisms? What is the rate?
- How long is the chemical in each medium?
- Is there a steady-state concentration distribution?
- Parameters for Fate & Transport
- KOC - partitioning between organic carbon and water
- high = bind tighter to soil or sediment
- Kd - partitioning between specific soil type and water, unadjusted for KOC.
- high = bind tighter to soil or sediment
- KOW - partitioning between water and octanol
- high = more likely to partition to octanol (and bioaccumulate).
- Solubility - upper limit of concentration in water
- high = more goes into solution
- Henry’s Law Constant - partitioning between air and water
- high = more volatile
- Bioconcentration Factor (BCF) - partitioning between biota and external media
- high = more to living tissue
- Media-Specific Half-Life - relative measure of persistence
- high = more persistent
* NORMALLY DON’T HAVE ALL VALUES *
- Exposure Point - Where exposure occurs. Where the receptor actually or potentially contacts contaminated media.
- Exposure Route - How a chemical crosses the interface between the environment and you.
- Direct Routes - Ingestion, Dermal Contact, Inhalation
- Indirect Routes - Ingestion of biota.
* Building a Conceptual Site Model
- Types
- Cartoon - Public likes; not detailed enough for completing risk assessment
- Stem and Leaf - Public hates; provides detail needed to complete risk assessment
- Building a Stem and Leaf Conceptual Site Model
- Parts - Proceed through each part identifying connections.
- Source
- Release Mechanism
- Primary Media
- Transport Mechanism
- Secondary Media
- Exposure Routes
- Receptors
- Tools
- Simple List of media and routes
- ATSDR Tables
- ASTM Flow Chart
Last Revised: September 15, 1997
claubergm@mindspring.com -- 15-Sep-1997