Risk CHARACTERIZATION Topic 6 Risk CHARACTERIZATION

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?)

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

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

SOIL TO AIR CONCENTRAITON CONVERSION

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

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

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

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.

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

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

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

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

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

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

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

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.

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

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

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% 365 - 350 = 15 15 / 500 = 0.04 Increased risk by 4% Estimated risk increase = 160% x 104% = 166%

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

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

Questions?