Introduction to Environmental rd Engineering and Science 3

Introduction to Environmental rd Engineering and Science (3 ed. ) Chapter 4. Risk Assessment Introduction to Environmental Engineering and Science: THIRD EDITION Gilbert M. Masters and Wendell P. Ela 0 -13 -601837 -8

Risk Assessment: National Academy of Science (1983) Introduction to Environmental Engineering and Science: THIRD EDITION Gilbert M. Masters and Wendell P. Ela 0 -13 -601837 -8

Risk Assessment 1. Hazardous identification: the process of determining whether or not a particular chemical is causally linked to particular health effects, such as cancer or birth defects. 2. Dose-response assessment: the process of characterizing the relationship between the dose of an agent administered or received and the incidence if an adverse health effect. Introduction to Environmental Engineering and Science: THIRD EDITION Gilbert M. Masters and Wendell P. Ela 0 -13 -601837 -8

Risk Assessment 3. Exposure assessment: determining the size and nature of the population that has been exposed to the toxicant under consideration and the length of time and toxicant concentration to which they have been exposed. 4. Risk characterization: the integration of the foregoing three steps, which results in an estimate of the magnitude of the publichealth problem. Introduction to Environmental Engineering and Science: THIRD EDITION Gilbert M. Masters and Wendell P. Ela 0 -13 -601837 -8

Nomenclature for toxic effects Introduction to Environmental Engineering and Science: THIRD EDITION Gilbert M. Masters and Wendell P. Ela 0 -13 -601837 -8

Fate of chemical toxicants in the body Introduction to Environmental Engineering and Science: THIRD EDITION Gilbert M. Masters and Wendell P. Ela 0 -13 -601837 -8

Hazardous Identification • Acute toxicity: effects that are caused within a short period of time after a single exposure to the chemical ↔ chronic toxicity • LD 50: dose that will kill 50% of a population • Mutagenesis: genotoxic, carcinogens teratogens (Figure 4. 5) • Carcinogenesis: initiation and promotion (Table 4. 7) Introduction to Environmental Engineering and Science: THIRD EDITION Gilbert M. Masters and Wendell P. Ela 0 -13 -601837 -8

Introduction to Environmental Engineering and Science: THIRD EDITION Gilbert M. Masters and Wendell P. Ela 0 -13 -601837 -8

Dose-response morality curves for acute toxicity Introduction to Environmental Engineering and Science: THIRD EDITION Gilbert M. Masters and Wendell P. Ela 0 -13 -601837 -8

Possible consequence of a mutagenic event Introduction to Environmental Engineering and Science: THIRD EDITION Gilbert M. Masters and Wendell P. Ela 0 -13 -601837 -8

Toxicity Testing in Animals 1. Ames mutagenicity assay (short-term test) 2. Intermediate testing (several months) 3. Chronic carcinogenesis bioassay - Two species of rodents (mica and rates) - At least 50 males/50 females for each dose - At least two doses + no-dose control (exposure 6 weeks of age to 24 months) Introduction to Environmental Engineering and Science: THIRD EDITION Gilbert M. Masters and Wendell P. Ela 0 -13 -601837 -8

Carcinogens: By U. S. EPA • Group A: human carcinogen • Group B: probable human carcinogen • Group C: possible human carcinogen • Group D: not classified • Group E: evidence of noncarcinogenicity Introduction to Environmental Engineering and Science: THIRD EDITION Gilbert M. Masters and Wendell P. Ela 0 -13 -601837 -8

Human Studies 1. Relative risk (>1 ? ) 2. Attributable risk (>0 ? ) 3. Odds ratio (>1 ? ) (Example 4. 1) Introduction to Environmental Engineering and Science: THIRD EDITION Gilbert M. Masters and Wendell P. Ela 0 -13 -601837 -8

Introduction to Environmental Engineering and Science: THIRD EDITION Gilbert M. Masters and Wendell P. Ela 0 -13 -601837 -8

Dose-Response Assessment • Dose-response curves: the results of chronic toxicity; the organism is subject to a prolonged exposure over a considerable fraction of its life • X-axis: dose (mg/kg-day); the average milligrams of substance per kilogram of body weight per day Introduction to Environmental Engineering and Science: THIRD EDITION Gilbert M. Masters and Wendell P. Ela 0 -13 -601837 -8

Hypothetical dose-response curves Introduction to Environmental Engineering and Science: THIRD EDITION Gilbert M. Masters and Wendell P. Ela 0 -13 -601837 -8

Two methods of fitting for doseresponse curves Introduction to Environmental Engineering and Science: THIRD EDITION Gilbert M. Masters and Wendell P. Ela 0 -13 -601837 -8

Potency Factor (PF) for Carcinogens • Incremental lifetime cancer risk = CDI×PF • CDI: chronic daily intake = average daily dose/body weight (4. 13) • Incremental lifetime cancer risk = an upperbound estimate of the actual risk (Table 4. 9, PF oral/inhalation) (Example 4. 2) Introduction to Environmental Engineering and Science: THIRD EDITION Gilbert M. Masters and Wendell P. Ela 0 -13 -601837 -8

Introduction to Environmental Engineering and Science: THIRD EDITION Gilbert M. Masters and Wendell P. Ela 0 -13 -601837 -8

Drinking Water Equivalent Level (DWEL) • To estimate the concentration of a contaminant in drinking water that would result in a politically acceptable risk level = 10 -6 • DWEL = the concentration that will produce that risk assumption: 70 kg, 2 -L of water /day (Example 4. 3) Introduction to Environmental Engineering and Science: THIRD EDITION Gilbert M. Masters and Wendell P. Ela 0 -13 -601837 -8

Introduction to Environmental Engineering and Science: THIRD EDITION Gilbert M. Masters and Wendell P. Ela 0 -13 -601837 -8

Rf. D (ADI), NOAEL, LOAEL, & threshold Introduction to Environmental Engineering and Science: THIRD EDITION Gilbert M. Masters and Wendell P. Ela 0 -13 -601837 -8

Rf. D, Hazard Index • Rf. D = NOAEL / (uncertainty factor) uncertainty factor = 10 -1000 • Hazard quotient = average daily dose during exposure period (mg/kg-day) / Rf. D • Hazard Index = Sum of the hazard quotients (>1, potential risk) Introduction to Environmental Engineering and Science: THIRD EDITION Gilbert M. Masters and Wendell P. Ela 0 -13 -601837 -8

Exposure Pathways Introduction to Environmental Engineering and Science: THIRD EDITION Gilbert M. Masters and Wendell P. Ela 0 -13 -601837 -8

Bioconcentration Factors (BCFs) Contaminant Degradation • Concentration in fish = concentration in water × BCF (Table 4. 12) (Example 4. 7) • Half-life (t 1/2) t 1/2 = ln 2/k = 0. 693/k Introduction to Environmental Engineering and Science: THIRD EDITION Gilbert M. Masters and Wendell P. Ela 0 -13 -601837 -8

Introduction to Environmental Engineering and Science: THIRD EDITION Gilbert M. Masters and Wendell P. Ela 0 -13 -601837 -8

Introduction to Environmental Engineering and Science: THIRD EDITION Gilbert M. Masters and Wendell P. Ela 0 -13 -601837 -8