Review Sheet #4
Environmental Risk Assessment:
Applications to Hazardous Waste Sites
EV-595 Fall 1997
Readings (old):
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)
Readings (New):
Risk Assessment Guidance for Superfund: Volume I - Human Health Evaluation Manual
(Part B, Development of Preliminary Remediation Goals) - All
Exposure Assessment:
* Three step process - Interrelated
Step 3 - Quantitation of Exposure
Last of three steps of exposure assessment
Results in calculation of estimates of dose
- Daily Intake
- Daily Adsorbed Dose
Definition of Dose (for risk assessment)
- The amount of material contacted (or absorbed) per unit body weight during a unit time.
Note:
General form of exposure equation:
where:
- I ----- Intake - amount of substance at exchange boundary or
Absorbed dose - amount of substance entering "bloodstream."
- C ----- Representative concentration in medium.
- CR ---- Contact Rate - amount of contaminated medium contacted per unit time or event.
- EFD --- Exposure Frequency and Duration - how long and how often exposure occurs
- BW ---- Body Weight - average body weight during term of exposure.
- AT ---- Averaging Time - period over which exposure is averaged.
Two parts of equation
- C (chemical-specific portion) and Bracketed (Exposure factor)
"Exposure factor" made-up of "exposure parameters" (e.g., CR, EFD, BW, AT).
Example - Ingestion of Drinking Water
where:
- Intake - Dose [mg/(kg × day)]
- Cw --- Concentration in water (mg/liter)
- IR ---- Amount of water drank per day (liters/day) *
- EF ---- Frequency of exposure (days/year) *
- ED ---- Duration of exposure (years) *
- BW --- Average body weight during exposure (kg) *
- AT ---- Averaging time (days) *
* these are the Exposure Parameters
Last Revised: September 28, 1997
claubergm@mindspring.com -- 28-Sep-1997