2: Conventional Risk Analysis outline established terms and methods in risk analysis show how different risks and technologies compare survey basis key regulatory concepts in risk management explain how risk analysis addresses subjectivity and information review strong points and set out key questions for next week
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2: Conventional Risk Analysis
outline established terms and methods in risk analysis
show how different risks and technologies compare
survey basis key regulatory concepts in risk management
explain how risk analysis addresses subjectivity and information
review strong points and set out key questions for next week
Some Working Definitions
A hazard is a property or situation that in particular circumstances
could lead to harm.
In economics, hazard can imply positive benefit as well as negative harm.
A probability is a numerical expression (between 0 and 1) of chance,
reflecting the likelihood that benefit or harm may arise from a hazard.
A condition of risk exists when a probability is assigned to the specific
forms or levels of harm resulting from a particular defined hazard.
(eg: nuclear reactor, chemical drum, ladder)
(eg: 50:50 chance, p = 0.5; 5 % chance, p = 0.05; 1/1000 chance, p = 0.001)
Risk therefore involves combined consideration of both the magnitude
and the likelihood of harm that may arise from a hazard.
Risk is usually expressed in terms of some measure of the duration,
extent, frequency or intensity of exposure to the hazard in question.
(eg: per affected actor; per unit time, per unit output, per instance, etc…)
The Key Idea in Risk Assessment
RISK = magnitude of harm x probability of harm
unit of exposure
nuclear power: 10,000 deaths x 0.01 % chance
every GW.year
= 1 death / GW.y
eg (hypothetically):
offshore wind: 1 death x 0.5 % chance
every 5 MW.year
= 1 death / GW.y
or (for a given unit of exposure): risk = probability x magnitude
A condition of uncertainty exists where there is no robust basis for
assigning probabilities to at least some of the relevant forms of harm.
Detailed Stages in Risk Analysis
HAZARD
IDENTIFICATION
HAZARD
CHARACTERISATION
RISK EVALUATION
RISK
MANAGEMENT
RISK
COMMUNICATION
INSTRUMENTS
AND MEASURES
PUBLIC AND
STAKEHOLDERS
‘OBJECTIVE’
SCIENCE
RISK
ESTIMATION
POLICY
CONSIDERATIONS
identify all possible relevant
sources of harm
establish relationship between
dose and response
quantify magnitudes and
probabilities of harm
EXPOSURE
ASSESSMENT
identify targets, quantify levels
and frequency of exposure
determine significance of risk
and weigh against benefits
Detailed Stages in Risk Analysis
HAZARD
IDENTIFICATION
HAZARD
CHARACTERISATION
RISK EVALUATION
RISK
MANAGEMENT
RISK
COMMUNICATION
INSTRUMENTS
AND MEASURES
PUBLIC AND
STAKEHOLDERS
‘OBJECTIVE’
SCIENCE
RISK
ESTIMATION
POLICY
CONSIDERATIONS
EXPOSURE
ASSESSMENT
RISK
ASSESSMENT
Detailed Stages in Risk Analysis
HAZARD
IDENTIFICATION
HAZARD
CHARACTERISATION
RISK EVALUATION
RISK
MANAGEMENT
RISK
COMMUNICATION
INSTRUMENTS
AND MEASURES
PUBLIC AND
STAKEHOLDERS
‘OBJECTIVE’
SCIENCE
RISK
ESTIMATION
POLICY
CONSIDERATIONS
EXPOSURE
ASSESSMENT
RISK
ASSESSMENT
HAZARD
IDENTIFICATION
Hazard Identification
Identify all possible relevant sources of harm, eg:
in chemicals regulation: carcinogenicity neurotoxicity
mutagenicity asthmagenicity
reproductive toxicity endocrine disruption
in occupational safety: flammability explosiveness
corrosiveness biohazard
radioactivity fissionability
in agricultural biotech: pathogenicity antibiotic resistance
weed tolerance novel allergenicity
horizontal transfer vertical transfer
nontarget effects co-existence effects
in engineering: cost over-run structural failure
construction injuries public safety
Detailed Stages in Risk Analysis
HAZARD
IDENTIFICATION
RISK EVALUATION
RISK
MANAGEMENT
RISK
COMMUNICATION
INSTRUMENTS
AND MEASURES
PUBLIC AND
STAKEHOLDERS
‘OBJECTIVE’
SCIENCE
RISK
ESTIMATION
POLICY
CONSIDERATIONS
EXPOSURE
ASSESSMENT
RISK
ASSESSMENT
HAZARD
IDENTIFICATION
HAZARD
CHARACTERISATION
HAZARD
CHARACTERISATION
Hazard Characterisation
?
No observed adverse effect level (NOAEL)
MAGNITUDE
OF HARM
(response)
eg:
Frequency of death
Monetary cost
Ecological impact
EXPOSURE TO HAZARD
(dose)
eg: Levels of emissions
Ambient concentrations
Frequency of activity
KEY REGULATORY CONCEPTS
Lowest observed adverse effect level (LOAEL)
The concept of dose - response
Some simple relationships between hazard and harm
MAGNITUDE
OF HARM
EXPOSURE TO HAZARD
Dose Response Curves
LINEAR
eg: ionising
radiation
THRESHOLD
eg: assumption for
many natural toxins
S-CURVE
eg: heavy metals
and kidney damage
Exposures and dose–response relationships can be stochastic or deterministic
Exposure assessment then determines probabilities of different exposures
Detailed Stages in Risk Analysis
HAZARD
IDENTIFICATION
RISK EVALUATION
RISK
MANAGEMENT
RISK
COMMUNICATION
INSTRUMENTS
AND MEASURES
PUBLIC AND
STAKEHOLDERS
‘OBJECTIVE’
SCIENCE
RISK
ESTIMATION
POLICY
CONSIDERATIONS
EXPOSURE
ASSESSMENT
RISK
ASSESSMENT
HAZARD
IDENTIFICATION
HAZARD
CHARACTERISATION
EXPOSURE
ASSESSMENT
Exposure Assessment
Some simple probability distributions for different levels of exposure
PROBABILITY
LEVEL OF EXPOSURE
NORMAL
eg: where
exposures random
with uniform mode
TYPICAL
eg: exposures
usually asymmetric
with ‘long tail’
POWER LAW
eg: where exposures
are complex and
diverse
Risk estimation can then determine probabilities of different levels of harm
log
log
Detailed Stages in Risk Analysis
HAZARD
IDENTIFICATION
RISK EVALUATION
RISK
MANAGEMENT
RISK
COMMUNICATION
INSTRUMENTS
AND MEASURES
PUBLIC AND
STAKEHOLDERS
‘OBJECTIVE’
SCIENCE
RISK
ESTIMATION
POLICY
CONSIDERATIONS
EXPOSURE
ASSESSMENT
RISK
ASSESSMENT
HAZARD
IDENTIFICATION
HAZARD
CHARACTERISATION
RISK
ESTIMATION
Risk Estimation
Some illustrative annual probabilities of death
Cause Basis Annual Probability
Members of the public population
All accidents (England, Wales,1992) 1 / 4,030
Road accidents (GB, 1995) 1 / 15,700
Gas accidents (GB, 1986-95) 1 / 1,350,000
Accidents at work all employees
Not self employed (GB, 1995-6) 1 / 100,000
Self employed (GB, 1995-6) 1 / 62,500
Quarries (GB, 1983-92) 1 / 5,500
Typical regulatory limits
For workers 1 / 1,000
For the general public 1 / 10,000
Live near hazardous facility 1 / 1,000,000
Risk Estimation
Comparing probabilities of different activities and events