1. International Open Nomiracle workshop, June 2006

Application of multi criteria methods in scenario selection

Peter B SørensenApplication of multi-criteria methods in scenario selection

What is a “scenario” in this context ?What is a “criteria” in this context ?Why is the work prior to the application of multi-criteria methods critical ?The best way from the problem towards the answerThe hidden uncertainty of risk assessment

1. International Open Nomiracle workshop, June 2006Peter B SørensenApplication of multi criteria methods in scenario selection

Definition of a scenario

Risk problem boundary includes the elements: Target The target that may be subject to harmful effects. The environmental target can be defined as a single organism,

a group of organisms or a specific eco-system. Condition for exposure The condition of exposure covers all the aspects other that the substance that has an influence on the exposure level. This include mixtures.Substances to be considered The space of substance needs to be clarified. Is the problem about a special group of chemicals based on their usage like e.g. pesticides or a chemical class like organophosphates or a single component?Other stressors To what extend will other stressors like temperature, UV radiation etc. be included as a part of the risk problem?

The risk scenario quantifies all elements within the risk problem boundary

Statement 1 There are not resources for risk assessment of all possible realistic risk scenarios so the most relevant scenario for risk assessment has to be identified before the risk level can be quantified.

Statement 2 A complete and thus certain identification of the most relevant risk scenario for risk assessment needs a prediction of risk levels for all possible scenarios.

Thus, it is impossible to find the most relevant risk scenario with compete certainty.

There is a danger that the most relevant scenario for risk assessment becomes hidden and thus risk assessment takes places on sub-optimal conditions

Violating precaution and probabilistic approaches in general

1. International Open Nomiracle workshop, June 2006Peter B SørensenApplication of multi criteria methods in scenario selection

The dilemma in complex risk assessment

1. International Open Nomiracle workshop, June 2006Peter B SørensenApplication of multi criteria methods in scenario selection

The system model consists of the following sub models:

• Model for problem specification (Problem Specification Model, PSM). Predicts a set of sub-problems that all has relevanse for the risk

estimation.

• Model for scenario composition (Scenario Composition Model, SCM). Predicts the set of sub-problems that are assumed mostly to govern the

scenario.

• Model for criteria compilation (Criteria Model, CM). Compiles the set of sub-problems into a set of criteria.

• Model for scenario selection (Scenario Selection Model, SSM). Predicts the highest risk scenarios based on the criteria values.

We need a system model for risk scenario design !!

1. International Open Nomiracle workshop, June 2006Peter B SørensenApplication of multi criteria methods in scenario selection

Problem Specification Model, PSM

Main problem

Sub problem 1 Sub problem 2

Sub problem 1.1 Sub problem 1.2 Sub problem 1.2 Sub problem 2.1 Sub problem 2.2 Sub problem 2.2

Not recognized but relevant sub problem:“Not recognized ignorance” type of uncertainty

Qualitative model

Human health

Effects when exposed Exposure level

Release Fate Body entranceChronic Acute Allergy

1. International Open Nomiracle workshop, June 2006Peter B SørensenApplication of multi criteria methods in scenario selection

Scenario Composition Model

Main problem

Sub problem 1 Sub problem 2

Sub problem 1.1 Sub problem 1.2 Sub problem 1.2 Sub problem 2.1 Sub problem 2.2

“Recognized ignorance” type of uncertainty

Increasing roughness

Ordinal model: More important/Lesser important

Human health

Effects when exposed Exposure level

Release FateChronic Acute Allergy

1. International Open Nomiracle workshop, June 2006Peter B SørensenApplication of multi criteria methods in scenario selection

Criteria Model

Ordinal model for each sub problem

Risk conditions Risk criteria

Estim

ation by em

pirical data and/or m

odels

Sub problem 1.1 Criteria 1: high/low value=high/low risk

Sub problem 1.2 Criteria 2: high/low value=high/low risk

Sub problem 2 Criteria 3: high/low value=high/low risk

Estimation uncertainty: condition “=“ Criterion

Chronic

Acute

Exposure level

R48: yes/no = high/low risk level

R23: yes/no = high/low risk level

Production volume (tons)high/low = high/low risk level

Human health

Criteria 1: high/low value=high/low risk

Criteria 2: high/low value=high/low risk

Criteria 3: high/low value=high/low risk

Highest risk scenarios

1. International Open Nomiracle workshop, June 2006Peter B SørensenApplication of multi criteria methods in scenario selection

Scenario Selection Model

Ordinal model for risk level

Multi-criteria modelR48: yes/no = high/low risk level

R23: yes/no = high/low risk level

Production volume (tons)high/low = high/low risk level

Benzenestoddard solventtoluene2-butoxyethanol---

Risk level

Value uncertaintyMulti-attribute uncertainty

1. International Open Nomiracle workshop, June 2006Peter B SørensenApplication of multi criteria methods in scenario selection

Probability for :X1>X4=0,66X1>X2=0,33

maximal multi-attribute uncertainty:

All possible multi-criteria models will select one and only one of the three linear extensions.

Scenarios Criteria Addition Multiplication

X1 2 7 2+7=9 2·7=14X2 3 5 3+5=8 3·5=15X3 7 7 7+7=14 7·7=49X4 3 4 3+4=7 3·4=12

X3

X2 X1

X4

X3

X2

X1

X

X3

X1

X2

X4

X3

X4

X2

X1

All possible rankings(Linear extensions)

The partial order(Hasse diagram)

4

Two multi-criteria models

Multi-attribute uncertainty

1. International Open Nomiracle workshop, June 2006Peter B SørensenApplication of multi criteria methods in scenario selection

Id 101Methyloxirane

Cas no. 75-56-9

Multi-attribute uncertainty

10 criteria case

1. International Open Nomiracle workshop, June 2006Peter B SørensenApplication of multi criteria methods in scenario selection

Statistical Learning Theory: Never solve a problem at an unnecessaryhigh complexity level as an intermediate step !!!

Conclude so much as possible before you are moving to a more detailed level

Increasing complexity

Problem Specification Model

Scenario Composition Model

Criteria Model

Scenario Selection Model

Risk level quantification

Increasing uncertainty

Only factor of uncertainty in “probabilistic risk assessment”

Main task in risk mapping