Intro to Risk Assessment

Risk Assessment Paradigm

What is risk?

the probability that a substance/situation will produce harm under specified conditions (probability that the event occurs AND consequences of event)

Exceedance probability vs risk

What are three uses/objectives for risk assessment?

1. ID hazards

2. Analyze/interpret risk

3. Determine/implement control measures

OR

1. meet regulation

2. meet cleanup criteria

3. meet the expected risk

Environmental risk assessment

process of making a quantitative estimate of human health risks resulting from release or potential release of contaminants to the environment

Problem statement

ask some type of question to lead to a scientific inquiry and hypothesis, can implicitly or explicitly mandate assumptions/methods

System description

qualitative and quantitative info about physical processes in system (timescale, geo and physical configuration), provides key info for risk calculation component

4 steps of environmental risk assessment calculation procedure with description

1. Release assessment (S_dot - contaminant emission rate) - ID of contaminants and quantitative estimation of release probabilities and rates

2. Transport assessment (C) - ID of pathways and estimation of contaminant concentration

3. Exposure assessment (D) - ID exposed populations and exposure routes and calc of rate/duration of exposure

4. Consequence assessment (risk) - adverse aesthetic, ecological, and human effects

Transport pathway vs exposure route

how contaminant moves through environment vs how contaminant moves through body

Aleatory uncertainty

related to chance

Epistemic uncertainty

related to knowledge

Assessment endpoint

valuable ecological or system characteristics you want to protect; all the way down to risk → more uncertainty

Measurement endpoint

measurable biological or physical indicators directly linked to those assessment endpoints that tell you if risk is present/changing; case study, stop and compare concentrations/values to literature

Conceptual model

abstraction of various physical, chemical, and biological processes that affect the behavior of the contaminant in the system

Mathematical model

mathematical representation of conceptual model which permits the calculation of assessment measures

Computational model

math model converted to this, usually identical to math model, calc of assessment involves substituting risk parameters into closed-form analytical expressions using rudimentary computational tool like calculator/spreadsheet

Verification

process of assuring that the math model is accurately translated into the computational model

Calibration

adjustment of risk parameters so that predictions of model match observations

Validation

comparison of predictions of computational model to actual field measurements

What are the appropriate units for radiological and chemical contaminant concentrations in air, soil, food, and water?

mass/time, activity/time