esm223_04_Lecture_Notes_smallsize

esm223_04_Lecture_Notes_smallsize - Winter 2008, Norm Brown...

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ESM 223 Lecture 4 – Risk Analysis and Hazardous Waste Sites Winter 2008, Norm Brown Administrative Reminders: All lecture notes and other digital documents: http://waterresourcescience.com Office Hours BH4408 - by appointment Email : nnbrown@gmail.com Course Texts : Watts; Reader Program • Crop Type • Rotation Frequency • Subwatershed • Tiling/Drainage Program Field Testing UWCD Pesticide Sampling • Organophosphate –More recent use –Relatively short half-lives –Reaches waterways by short-circuit • Chlorinated –Legacy usage –Relatively long half-lives –Moves with organic material in sediment
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Nutrient BMPs • Eliminate prescribed applications • Don’t apply when leaching can occur • Tighten irrigation practices to reduce runoff and excessive leaching – match to crop water demand • Capture storm runoff • Conduct regular maintenance of irrigation system 6 Toxicity Assessment • Objective: quantitatively determine the potential for adverse health effects as a result of exposure to the contaminants – Hazard assessment: determine if exposure causes an increase in the incidence of an adverse health effect (e.g. cancer, birth defects) – Dose-response assessment: quantitative evaluation of toxicity and characterization of the dose-response relationship Toxicity Assessment 8 Toxicity Assessment • Threshold vs. Non-threshold – Some pollutants require an exposure above a threshold level or dose during a continuous exposure episode to cause toxic effects Percent of Organisms Responding
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Toxicity Assessment Toxicity Assessment See Table 10.2 in Watts for specific LD 50 values 11 Toxicity Assessment • Carcinogenic vs. Non-carcinogenic • NOTE: Carcinogens may also provoke other toxic effects (i.e. may also have non-carcinogenic risk) – EPA categories for carcinogens: • A Known human carcinogen • B1 Limited human evidence • B2 Sufficient evidence in animals, but insufficient in humans • C Possible human carcinogen • D Not classifiable as human carcinogen • E No evidence of carcinogenicity 12 Toxicity Assessment: Non-carcinogens • Reference Dose (RfD) – Maximum amount of a chemical that an organism can absorb without experiencing chronic health effects – Provides estimate of continuous daily exposure for the general population (including sensitive groups) without an appreciable deleterious effect – Units are [mg/kg body weight - day] • Acceptable Daily Intakes (ADI) – Experimentally determined from “Lowest Observable Adverse Effect Level” (LOAEL)
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13 Toxicity Assessment: Non-carcinogens • Sample calculation of RfD: – A study is made with 250 rats that determines that there is “No Observable Adverse Effect” (NOAEL) at 5 mg/kg-day – The RfD is calculated as follows: – Uncertainty factor (UF): • Use a factor of 10 for extrapolating from valid experiments to prolonged exposure of healthy humans, accounting for sensitivity. (10H) RfD NOAEL UF x MF = 14 Toxicity Assessment: Non-carcinogens – Use another factor of 10 when extrapolating
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esm223_04_Lecture_Notes_smallsize - Winter 2008, Norm Brown...

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