Department of Civil Engineering
Southern Illinois University Carbondale
Instructor: Jemil Yesuf
Dr. L.R. Chevalier
Lecture Series 10:
Hazardous Waste Risk Assessment

 Review the history and impact of environmental laws in the
United States
 Understand the terminology, nomenclature, and significance of properties of hazardous wastes and hazardous materials
 Develop strategies to find information of nomenclature, transport and behavior, and toxicity for hazardous compounds
 Elucidate procedures for describing, assessing, and sampling hazardous wastes at industrial facilities and contaminated sites
 Predict the behavior of hazardous chemicals in surface impoundments, soils, groundwater and treatment systems
 Assess the toxicity and risk associated with exposure to hazardous chemicals
 Apply scientific principles and process designs of hazardous wastes management, remediation and treatment

 The ultimate goal is to provide a quantitative basis for making decisions involving

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 hazardous waste treatment
Remediation
Disposal options
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Waste minimization
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Siting new facilities (incinerators, Landfill)
 Is a key part of CERCLA and SARA
 See page 519 for two extremes of risk

 Chance of encountering the potential adverse effects of human and ecological exposures to environmental hazards
 Put simply;
RISK = TOXICITY x EXPOSURE
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Toxicity = contaminant’s ability to cause adversity
Exposure = The route to receptors and the concentration of the contaminant

4 Steps for Risk Assessment (EPA)
 Hazardous Identification
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What chemicals exist at the site and are of potential concern?
 Exposure assessment
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How might a receptor be exposed on or off site?
 Toxicity Assessment

At what level of exposure are adverse effects likely to occur? – Receptor analysis
 Risk Characterization

What are the risks and uncertainties at the site? – e.g. one in hundred, or one in one million

Data Collection and Evaluation
Exposure Assessment Toxicity Assessment
Risk
Characterization

 What human receptors are near your site?
 Are residential properties close by?
 Is site access restricted?
 What contaminants are present?
 Is there a threat or demonstrated release?
 What media have been impacted?
 What data are available?

 Identify and estimate concentrations of chemicals potentially affecting human health or ecological receptors
 Characterize the site in terms of:

Physical characteristics
 Soil characteristics, surface water location, groundwater (flow depth), meteorology
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
Exposed populations

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Human activities and land use (recreation, residential/industrial/commercial)
Proximity to release
Potential future uses

 Identify exposure pathways
 Develop a conceptual site model
 Determine amount of exposure for each pathway using monitoring data or fate and transport models
 Analyze concentrations, frequency and duration of contaminant exposure to population groups
 Consider characteristics of affected population groups - age of individuals, age, unique exposure considerations, other factors

 Compare dose of contaminant with incidence of adverse human health effect to ascertain relationship (quantitative toxicology)
 Determine whether exposure to certain chemicals results in adverse health effects
 Evaluate available toxicity information

Databases - IRIS (EPA)
 Identify data gaps
 Investigate human health problems near the site

 Combine information gathered in the
Exposure Assessment and Toxicity
Assessment
 Quantify risks to human health from individual chemicals and exposure pathways
 Sum risks for various exposure scenarios

Evaluate cancer risk, non-cancer hazard separately (Eqns. 11.8 and 11.9 Textbook)
 Describe all assumptions, areas of uncertainty

 RCRA and CERCLA requires EPA to remediate uncontrolled hazardous waste sites in a way that protect both human health and the
ENVIRONMENT.
 National Contingency Plan requires that the four steps be used for risk assessment to characterize the current and potential threats to both public health and the
ENVIRONMENT.

 Reduction in population size
 Change in community structure
 Changes in ecosystem structure and function

 Source characterization
 Lack of available data
 Exposure assessment models and methods
 Toxicology data

 Risk assessment – unbiased scientific approach to assessing risk
 Risk management – incorporates the results of risk assessment, factors in societal values, legal mandates, other considerations
 Risk communication is a critical piece of each of these

The process of weighing policy alternatives and selecting the most appropriate regulatory action by integrating the results of risk assessment with engineering data in addition to social, economic, and political concerns to reach a decision.

 Human response to risk is not always rational
 Level of risk play little role in acceptability to public
 Emotional response often makes it difficult to communicate risk
 People apply personal values when evaluating risk

 Voluntary vs. Involuntary
 Familiar vs. Unfamiliar
 Visibility of Threat
 Catastrophic vs. Non-catastrophic
 Natural vs. Man-made
 Affects Adults vs. Children
 Trusted vs. Untrusted Communicator
 Equal vs. Unequal Benefits

 Accept and involve the public as a legitimate partner
 Plan and carefully evaluate communication efforts
 Identify audience, understand problems, pretest message
 Listen to public’s specific concerns
 Be honest, frank and open

 Coordinate and collaborate with other credible sources
 Meet needs of media
 Speak clearly and with compassion