Presentation on theme: "CE 510 Hazardous Waste Engineering"— Presentation transcript:
1 CE 510 Hazardous Waste Engineering Department of Civil EngineeringSouthern Illinois University CarbondaleInstructor: Jemil YesufDr. L.R. ChevalierLecture Series 9:Quantitative Toxicology
2 Course GoalsReview the history and impact of environmental laws in the United StatesUnderstand the terminology, nomenclature, and significance of properties of hazardous wastes and hazardous materialsDevelop strategies to find information of nomenclature, transport and behavior, and toxicity for hazardous compoundsElucidate procedures for describing, assessing, and sampling hazardous wastes at industrial facilities and contaminated sitesPredict the behavior of hazardous chemicals in surface impoundments, soils, groundwater and treatment systemsAssess the toxicity and risk associated with exposure to hazardous chemicalsApply scientific principles and process designs of hazardous wastes management, remediation and treatment
3 Generalized Concepts Classification of repeated exposure AcuteSubchronicChronicDistinction based on average life expectancyAcute (1 day)Subchronic (2 weeks-7 years)Chronic (> 7 years)Common example would be exposure to a lifetime of drinking water contaminated with trace levels of a hazardous waste
4 Generalized Concepts Mechanisms of Toxicity Oral, dermal, inhalationVariability in biological communitiesAnatomy, physiology, biochemistryBased on genetics as well as environment
5 Definitions LD50 Threshold Limit Values, TLV Lethal dose to 50% of populationUsed to quantify acute toxcityThreshold Limit Values, TLVUsed to quantify chronic exposure limitsMaximum Contaminant Level, MCLUsed to regulate drinking water under Safe Drinking Water Act
7 Quantification of Acute Toxcity, LD50 ApproachDivide population of animals into a number of subgroupsAdminister progressively higher dosages of the toxic substance to each groupAfter toxin is administered, the number of deaths within each group are recorded over a specified period
8 Quantification of Acute Toxcity, LD50 Here, x is the dose and f(x) is the number of lethal responses.These values of the average and standard deviation allow us to predict the normal distribution of the population. The equation is on the next slide.
9 Quantification of Acute Toxcity, LD50 The apex of the curve generated by this equation is LD50
10 Example Spreadsheet solution to Example 10.2 Dose (mg/kg) Death 5 4 10 5410915142016251130357406452501Spreadsheet solution to Example 10.2
13 Probit AnalysisMore useful, more common method of computing LD50 and other toxicological parametersStands for probability unitTransforms sigmoidal curves of dose-response relationships to straight linesProbits are simply deviations from the mean of a normal distribution with a standard deviation of 1 and a mean of 5. In theory, the relationships between probabilities and probit are derived from the cumulative distribution curve
15 Probit Analysis Excel command for Probit =NORMINV(Cell/100,5,1) See Table 10.4 p. 498
16 ExampleAn acute bioassay exposed mealworms to various concentrations of the organochlorine insecticide endosulfan. Apply a probit analysis to the following data to calculate the LD50 . A total of 20 mealworms were used to initiate each treatment. Cumulative mortality (No. Dead) is shown after 96 hr.
19 Threshold Limit Value, TLV Used to measure chronic industrial exposureChronic toxicity is difficult to quantifyLess is known about long-term effectsThree categories of TLVTime-weighted average, TLV-TWAAverage for 8-hr work day (40-hr week)Used to determine the exposure over along periods without adverse effects (equation on next slide)Short-term exposure limit, TLV-STELMaximum concentration for exposure for repeated periods of up to 15 minutesCeiling, TLV-CConcentration that cannot be exceeded at any time
20 TLA-TWA Ta = time of first exposure period (hrs) Ca = contaminant concentration during the first periodTb…Tn = succeeding time periods (hrs)Cb…Cn = contaminant concentrations during the succeeding time periods
21 TLV DataAmerican Conference of Governmental Industrial Hygienists, ACGIHResource for dataGaseous and particulate airborne chemicalsPhysical factorsHeatUltraviolet lightIonizing radiation
23 TLV DataIf more than one chemical is present (common at hazardous waste sites)Toxic effects are assumed to be additiven = number of hazardous chemicalsCi = concentration of chemical i
24 Example refer to example 10.4, p. 505 Determine the mixture TLV-TWA for a worker exposed to 40 ppm n-octane, 40 ppm benzene, 40 ppm toluene and 40 ppm PCE in the air of a RCRA solvent recycling operation. Are the concentrations of the chemicals exceeding the TLV-TWAmixture?
27 Summary of Important Points and Concepts Toxic effects are classified based on duration of exposure, the most common exposure periods are acute, subchronic and chronicThe lethal dose of 50% of the population (LD50) is the most common indicator of acute toxicity. The LD50 is used to evaluate potential toxicity during one-time exposures too high concentrations of contaminants, such as hazardous material spills.Determination of the LD50 is accomplished by dosing population sets of organisms with succeedingly higher concentrations of a toxic chemical. The sigmoidal cumulative response to the dosages given is usually transformed to probits as a basis for determining the LD50Threshold Limit Values (TLVs) were developed for exposures to individuals in the workplace. They are a policy-related parameter based on a no-effect threshold during an 8-hour daily exposure over a working lifetime