1. Risk CHARACTERIZATION
Topic 6
Risk CHARACTERIZATION

2. overview Risk characterization
Average daily dose (ADD) and Lifetime average daily dose (LADD)
Vapor intrusion
Hazard index (hi) and Lifetime incremental cancer risk(licr)
Uncertainties
Review pea process
Review for midterm #2 (in-class or on-line?)

3. Risk characterization
Final step of a risk assessment
Integrates information from previous steps
Calculation of quantitative estimates of probability of an adverse health effect in a receptor
Chemicals causing Non-cancer health effects are presented as a hazard index
Carcinogenic chemical health effects are presented as a lifetime incremental cancer risk and compared to a one in a million cancer risk
Include and explain uncertainties in the assessment

4. SOIL RISK AND HAZARD INDEX
Contaminated soil is evaluated by comparing the maximum soil concentration of a chemical to its generic screening level to derive the cancer risk and/or hazard posed by that concentration
Cancer risk calculated is a summation of the incidental soil ingestion exposure for a child and an adult, and the dermal exposure for a child and an adult
Hazard is calculated for the first 6 years of childhood.
If the Hazard index (HI) is not exceeded for the child, it will not be exceeded for any other age.
equations do not include exposure from ingestion of homegrown fruits and vegetables, or products from animal (e.g., meat, milk, eggs) that feed on vegetation grown on contaminated soil

7. SOIL TO AIR CONCENTRAITON CONVERSION

10. EXAMPLE #1 – 1,4 DIOXANE LADD / ADD
Soil is contaminated with 1,4 - dioxane. Maximum soil concentration detected C = 100 mg/kg. What are the child oral, dermal, and inhalation ADD’s and lifetime LADD’s estimates?
EPA IRIS values for 1,4-dioxane are:
RfD oral = 3 x 10-2 mg/kg/day (also used for dermal)
RfC inhal = 3 x 10-2 mg/m3
Cancer slope oral = 1x10-1 mg/kg/day (also used for dermal)
Cancer Inhalation Unit Risk = 5 x 10-6 ug/m3

11. EXAMPLE #2 – STYRENE ADD only
Soil is contaminated with styrene. Maximum soil concentration detected C = 500 mg/kg. What are the child oral, dermal, and inhalation ADD estimates.
EPA IRIS values for Styrene are:
RfD oral = 0.2 mg/kg/day (also used for dermal)
RfC inhal = 1 mg/m3

12. EXAMPLE #3 – BROMOFORM LADD only
Soil is contaminated with bromoform. Maximum soil concentration detected C = 990 mg/kg. What are the lifetime oral, dermal, and inhalation LADD estimates.
EPA IRIS values for Styrene are:
Oral SF = 7.9 x 10-3 mg/kg/day (also used for dermal)
Inhalation SF = 1.1 x10-6 ug/m3

13. WATER RISK AND HAZARD INDEX
maximum groundwater concentration of a chemical is compared to tap water RSL.
Voc’s vs non-voc’s:
Only ingestion and dermal exposures are used in calculating Hi’s and cancer risk for non- voc’s
Voc’s include all ingestion, dermal and inhalation exposure pathways
Lifetime risk is calculated is a summation of ingestion exposure, inhalation of VOCs released from water used indoors, inhalation of vapors migrating indoors from groundwater, and dermal exposure, for child and adult.
Hazard index is calculated is a summation of ingestion exposure, dermal exposure, inhalation of VOCs released from water used indoors, and inhalation of vapors migrating indoors from groundwater for children
These equations do not include exposure from ingestion of aquatic organisms
THE Chemical- specific permeability coefficient (Kp values) used in water equations may be found in the Estimation Programs Interface (EPI) Suite DEVELOPED BY US EPA.

18. WHAT IS VAPOR INTRUSION?
ACCOUNTS FOR VOLITILE ORGANIC Cs in indoor air THAT may be present as the result of volatilization of compounds intruding indoors from sub-surface soil
The inhalation of indoor air contaminated by vapors coming from soil is the overriding exposure pathway for VOCs
attenuation factor = ratio of indoor air concentration to subsurface concentration, is used as a measure of the decrease in concentration that occurs during vapor migration
Not a factor for outdoor exposures

20. SOIL VAPOR CONCENTRATION DERIVED FROM GROUNDWATER CONCENTRATION (VOC’S ONLY)

21. INDOOR AIR CONCENTRATION DERIVED FROM SOIL VAPOR CONCENTRATION (VOC’S ONLY)

22. Water example #1
groundwater is contaminated with inorganic arsenic. Maximum concentration detected C = 4 mg/l. What are the child oral, dermal, and inhalation ADD’s and lifetime LADD’s estimates?
EPA IRIS values for inorganic arsenic are:
RfD oral = 3 x 10-4 mg/kg/day (also used for dermal)
Drinking water unit risk = 5 x 10-5 per ug/l (also used for dermal)
Permeability coefficient (Kp) = 1x10-3 cm/hr

23. Water example #2
groundwater is contaminated with 1,4 - dioxane. Maximum concentration detected C = 2 mg/l. What are the child oral, dermal, and inhalation ADD’s and lifetime LADD’s estimates?
EPA IRIS values for 1,4-dioxane are:
RfD oral = 3 x 10-2 mg/kg/day (also used for dermal)
RfC inhal = 3 x 10-2 mg/m3
Drinking water unit risk = 2.9 x 10-6 per ug/l (also used for dermal)
Cancer Inhalation Unit Risk = 5 x 10-6 per ug/m3
Residential screening level = 0.49 ug/l
Henry’s coefficient = 4.8 x 10-6
Permeability coefficient (Kp) = 3.4 x 10-4 cm/hr

24. Without default values
Any value can be used in the hazard and cancer risk equations, you just need to justify why
Example:
Calculate the hazard index for malathion in open soil at a maximum concentration of 200 mg/kg.
Use these values in the equation:
C=200mg/kg af = 1 mg/cm2
Ir=200mg/day sa= 2900 cm2/day
Ef=365 days/yr abs= 0.75
Ed=12 years
bw=15 kg
At= 12yrs x 356days/yr = 4380 days

25. Uncertainty analysis
Detailed explanation of the systematic and random errors of a measurement or estimate
Analytical process to provide information regarding the uncertainty in the risk assessment (which they all have)
Purpose is transparency
Give information about the uncertainty/ variability
Analyst has the responsibility to be clear about assumptions made

26. Qualitative vs quantitative
Uncertainty can be qualitative or quantitative.
Qualitative uncertainty may be due to a lack of knowledge about the factors that affect exposure
quantitative uncertainty may come from the use of non-precise measurement methods which lead to over- or under- estimation of risk
Uncertainty can be introduced when defining exposure assumptions, identifying individual parameters (i.e., data), making model predictions, or formulating judgments of the risk assessment.

27. Types of uncertainties
Compare risks for upper and lower confidence limits to calculate excess risks
Plausibility analysis = Compare your assessed risk to national rates
Safety factor uncertainty
Chemical concentrations in environmental media can be approximated using assumptions (more uncertainty) or described using measured data (less uncertainty).
In a screening risk assessment, focuses mainly on site specific conditions that significantly contribute to uncertainties

28. Qualitative uncertainty
Site conditions / Description errors
Professional judgment errors
Incomplete analysis
Measurement or sampling errors
Model uncertainty (parameter uncertainty, selection of incorrect model)

29. Quantitative Uncertainty
quantitative/ deterministic uncertainty= numeric, point-estimate of assumptions; usually represented as percentage increase of risk
Max concentration of 500 mg/kg vs average concentration of 200 mg/kg
500 – 200 = 300
300 / 500 = 0.60
increases hazard by 60%
Assuming 365 days instead of 350 days of exposure increased risk by 5%
= 15
15 / 500 = 0.04
Increased risk by 4%
Estimated risk increase = 160% x 104% = 166%

30. The pea report 1. Introduction to issue 2. Background research history
3. Conceptual site models
4. Data collection / sampling and data evaluation
5. Human health screening risk assessment
-calculations
-uncertainties
6. Opinion / conclusions / recommendations for site

31. REVIEW Average daily dose (ADD) and Lifetime average daily dose (LADD)
Vapor intrusion
Hazard index (hi) and Lifetime incremental cancer risk(licr)
Uncertainties
Review pea process
*Review for midterm #2

32. Questions?