arshad ahmad [email protected] 1 global 1 · localized individual risk (lira): the probability that an...

www.utm.my innovative ● entrepreneurial ● global 1 Arshad Ahmad

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● Risk to People ● Risk Matrix ● Risk Acceptance Criteria ● Voluntary Vs Involuntary Risks


A single death is a tragedy, a million deaths is a statistic.

Joseph Stalin


●  In the context of risk assessment, an indicator is a quantity that provides information about the level of risk

●  Risk indicator –  A parameter that is estimated based on risk analysis models and

by using generic and other available data. A risk indicator presents our knowledge and belief about a specific of the risk of a future activity or a future system operation

●  Safety performance indicator –  A parameter that is estimated based on experience data from a

specific installation or an activity. A risk performance indicator therefore tells us what has happened

●  Risk indicators are used to assess (prospective) risk, whereas safety performance indicators are used mainly for monitoring purposes

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●  Individual risk is the risk that an individual person is exposed to during a specific time period (usually, one year). Individual risk does not depend on the number of people who are exposed to the hazard.

●  Group risk is the risk experienced by a group of people. The group risk is a combination of individual risk levels and the number of people at risk, that is, the population being exposed.


●  Individual risk is the risk that an individual person is exposed to during a specific time period (usually, one year).

●  Individual risk is usually addressed in terms of a hypothetical or statistical person, who is an individual with some defined, fixed relationship to the hazard.

●  Individual risk does not depend on the number of people who are exposed to the hazard.

●  Individual risk: The frequency with which an individual may be expected to sustain a given level of harm from the realization of specified hazards (IChemE, 1992)


●  IRPAi = Pr(individual is killed due to hazards i during one year's exposure)

●  IRPAi may be estimated based on the number of fatalities observed in a specified time period for a specific group of individuals who have been exposed to the same hazards i,

IRPAi = Observed no. of fatallities due to hazards i

total no. of person- years exposed


“Federal traffic officer chief, SAC Mohd Fuad Abdul Latiff said there were 5138 deaths this year compared to 5357 during the same period last year.” (The Star, Tuesday, Oct 2014) IRPAi = 5138

30000000= 1.7127 x 10-4 fatalities per person per year

This means that in a group of 10000 people on average almost 2 person got killed in 2014 in Malaysia. This is an individual risk. NOTE: •  This is an average figure for Malaysia. A much higher value is

expected in peninsular Malaysia •  This number is the average value for a person at random, among

all inhabitants of Malaysia


Consider a person who is traveling by air between two cities n times a year. The frequency of accidents on this stretch has been estimated to be A. The IRPA for this activity is then

IRPAi = λ . Pr(the person on board of flight) . Pr (the person killed | the person is on board)


●  Localized individual risk (LIRA): The probability that an average unprotected person, permanently present at a specified location, is killed in a period of one year due to an accident at a hazardous installation (e.g., see Jonkman et al., 2003)

●  LIRA is also called individual risk (LSIR) and Individual risk index, and is used mainly for land-use planning.

LIRA i (x,y) = λi . Pr (fatality at (x,y) | Ai ) for i = 1,2,...,n

LIRA (x,y) = λi . Pr (fatality at (x,y) | Ai ) . a

i=1

n

∑

LIRA (x,y) = λi . Pr (fatality at (x,y) | Ai )

i=1

n

∑

LIRA for an individual event

The total LIRA at location (x,y) due to the hazardous installation

LIRA may also consider the proportion of time a the individual is actually present at location (x,y)


Hazardous Installation

1 x 10-4

1 x 10-5

1 x 10-6

Criteria for Land Use in Malaysia (LSIR) Industrial receptors < 1 x 10-5 Residential receptors < 1 x 10-6


Exposure Type Risk Level Hospitals, schools, child-care facilities, nursing homes Residential & places of continuous occupation (hotels/resorts) Commercial developments, including offices, retail centers, ware-houses with showrooms, restaurants and entertainment centers. Sporting complexes and active open space areas Industrial sites

Less than 5 x 10-7

Less than I x 10-6

Less than 5 x 10-6

Less than I x 10-5

Less than 5 x10-5


If a person dies at age t due to an accident, the RLE, is defined as RLEt=t0 - t where to denotes the mean life length of a randomly chosen person of the same age as the person killed, who has survived up to age t.

Cause Days Heart Disease 2100 Cancer 980 Stroke 520 Motor Vehicle Accidents 207 Accidents at home 95 Average jobs accidents 74 Drowning 41 Accidents to pedestrian 35

Source: Fischoff et al. (1981)


●  A lost-time injury (LTI) is an injury that prevents an employee from returning to work for at least one full shift. The frequency of LTis is often used as a safety performance indicator and is defined as

!!LTIF = no!of !LTI

no!of!hours !.!2.105


●  Lost Workdays Frequency. The LTIF does not weight the seriousness of the injury, so a fatal accident has the same effect on the LTIF as does a broken finger. The seriousness of an LTI may be measured by the number of workdays lost due to the LTI, and the lost workdays frequency, LWF, may alternatively be used as a safety performance indicator. The LWF* is defined as

!!LWF = no!of!loss!workdays!due!to!LTI!!no!of!hours!worked !.!2.105


Bird and Germain (1986) reports 1 serious or disabling injury 10 minor injuries 30 property damage accidents (all types) 600 incidents with no reported injury or damage (near misses)


●  Potential loss of life (PLL): The PLL is the expected number of fatalities within a specified population (or within a specified area A) per annum.

●  PLL for a Specified Population. Assume that all the members of a

population have the same individual risk per annum, IRPA. Let n denote the number of members of the population. The PLL is then determined by

●  PLL in Norway (example) !!PLLA = n.IRPA

!!PLLA = IRPA(x , y)m(x , y)dxdy

A∫∫

Type of Occupation PLL Agriculture Transport & Communication Construction Health & Social Services

9.4 7.2 6.4 1.6


●  Fatal accident rate (FAR): The expected number of fatalities in a defined population per I00 million hours of exposure.

●  Experienced FAR* !!FAR = expected!no!of!fatalities

no!of!hours!exposed!to!risk !.!108

!!FAR* = observed!no!of!fatalities

no!of!hours!exposed!to!risk !.!108


Type of Occupation FAR (Fatalities per 108 working hours)

Agriculture, forestry, fishing, and hunting Industry, manufacturing Building and construction Trade, restaurant, and hotel Transport, post, and telecommunication Banking and insurance Private and public services, defense, etc.

6.1 2.0 5.0 1.1 3.5 0.7 0.6

Experienced FAR (Nordic Country: 1980-1989)


Type of Occupation FAR (Fatalities per 108 working hours)

Factory Work (average) Construction (Average) Construction(high rise erector) Manufacturing (all) Oil & gas extraction Travel by car Travel by air (fixed wing) Travel by helicopter Rock climbing while on rock face)

4 5 70 I 15 30 40 500 4000

Experienced FAR (UK: 1980-1989) – Hambly (1992)


●  Group risk is the risk experienced by a group of people. When common citizens are exposed, the group risk is often called societal risk.

●  The group risk is a combination of individual risk levels and the number of people at risk, that is, the population being exposed.

●  Societal risk: The relationship between frequency and the number of people suffering from a specified level of harm in a given population from the realization of specific hazards (IChemE, 1992).


(HSE, 2001, Reducing Risks, Protecting People: HSE's Decision-Making Process )

Industry Sector Annual Risk Annual Risk

Fatalities to employees Fatalities to self-employed Mining and quarrying of energy producing materials Construction Extractive and utility supply industries Agriculture, hunting, forestry, and fishing (not sea fishing) Manufacture of basic metals and fabricated metal products Manufacturing industry Manufacture of electrical and optical equipment Service industry

1 in 125000 1 in 50000 1 in 9200 1 in 17000 1 in 20000 1 in 17200 1 in 34000 1 in 77000 1 in 500 000 1 in 333000

8.10-6

20.10-6

109.10-6

59.10-6

50.10-6

58.10-6 29.10-6

13.10-6

2.10-6 3.10-6


●  The FN curve may be used for at least three purposes: –  To show the historical record of accidents –  To depict the results of quantitative risk assessments –  To display criteria for judging the tolerability or acceptability of

outputs from quantitative risk assessments

Frequency of "excedance," meaning that F(n) denotes the frequency of accidents where the consequence is n or more fatalities.

!!F(n)= λ[N≥n] = λ.Pr(N ≥n)


Risk = Likelihood x Severity

Likelihood of Occurrence -  Frequency -  Probability

Severity of the Consequence -  Fatality, loss, illness, etc. -  Impact

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●  A risk matrix is a tabular illustration of the frequency and severity of hazardous events or accident scenarios. The risk matrix may be used to rank hazardous events according to their Significance, to screen out insignificant events, or to evaluate the need for risk reduction for each event (e.g., see HSE, 2001).

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Description Category Environmental, Safety and Health Result Criteria

Catastrophic I Death, permanent total disability Loss of exceeding $1M Irreversible severe environmental damage that violates law or regulation

Critical II Permanent partial disability, injuries or occupational illness that may result in hospitalization of at least 3 personnel Loss exceeding $200K but less than $1M Reversible environmental damage causing a violation of law or regulation

Marginal III Injury or occupational illness resulting in one or more loss of workdays Loss exceeding $10K but less than $200K Mitigatible environmental damage without violation of law or regulation where restoration activities can be accomplished

Negligible IV Injury or illness not resulting in a lost work day Loss exceeding $2K but less than $10K Minimal environmental damage not violating law or regulation

Source: MIL-STD-882D


Description Level Specific Individual Item Fleet or Inventory

Frequent A Likely to occur than 10-1 in that life Continuously experienced

Probable B Will occur several times in the life on an item, with probability of occurrence less than 10-2 but greater than 10-3 in that life

Will occur frequently

Occasional C Likely to occur some time in the life of an item, with a probability of occurrence less than 10-2 but greater than 10-3 in that life

Will occur several times

Remote D Unlikely but possible to occur in the life of an item with a probability of occurrence less than 10-3 but greater than 10-6 in that life

Unlikely but can be reasonably expected to occur

Improbable E So unlikely, it can be assumed occurrence may not be experienced, with a probability of occurrence less than 10-6

Unlikely but possible

Source: MIL-STD-882D


MIL-STD-882E

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TABLE I. Severity categories

SEVERITY CATEGORIES

Description Severity Category Mishap Result Criteria

Catastrophic 1 Could result in one or more of the following: death, permanent total disability, irreversible significant environmental impact, or monetary loss equal to or exceeding $10M.

Critical 2 Could result in one or more of the following: permanent partial disability,injuries or occupational illness that may result in hospitalization of at least three personnel, reversible significant environmental impact, or monetary loss equal to or exceeding $1M but less than $10M.

Marginal 3 Could result in one or more of the following: injury or occupational illness resulting in one or more lost work day(s), reversible moderate environmental impact, or monetary loss equal to or exceeding $100K but less than $1M.

Negligible 4 Could result in one or more of the following: injury or occupational illness not resulting in a lost work day, minimal environmental impact, or monetary loss less than $100K.

b. To determine the appropriate probability level as defined in Table II for a given

hazard at a given point in time, assess the likelihood of occurrence of a mishap. Probability level F is used to document cases where the hazard is no longer present. No amount of doctrine, training, warning, caution, or Personal Protective Equipment (PPE) can move a mishap probability to level F.

TABLE II. Probability levels

PROBABILITY LEVELS

Description Level Specific Individual Item Fleet or Inventory

Frequent A Likely to occur often in the life of an item. Continuously experienced.

Probable B Will occur several times in the life of an item. Will occur frequently.

Occasional C Likely to occur sometime in the life of an item. Will occur several times.

Remote D Unlikely, but possible to occur in the life of an item. Unlikely, but can reasonably be expected to occur.

Improbable E So unlikely, it can be assumed occurrence may not be experienced in the life of an item. Unlikely to occur, but possible.

Eliminated F Incapable of occurence. This level is used when potential hazards are identified and later eliminated.

Incapable of occurence. This level is used when potential hazards are identified and later eliminated.

(1) When available, the use of appropriate and representative quantitative data that

defines frequency or rate of occurrence for the hazard, is generally preferable to qualitative analysis. The Improbable level is generally considered to be less than one in a million. See Appendix A for an example of quantitative probability levels.


Qualitative Safety Consequence Criteria 4 Onsite or offsite: Poten.al for mul.ple life-‐threatening injuries or fatali.es.

Environment: Uncontained release with poten.al for major environmental impact Property: Plant damage value in excess of $100 million

3 Onsite or offsite: Poten.al for a single life-‐threatening injury or fatality. Environment: Uncontained release with poten.al for moderate environmental impact Property: Plant damage value in the range of $10-‐100 million

2 Onsite or offsite: Poten.al for an injury requiring a physician's care. Environmental: Uncontained release with poten.al for minor environmental impact Property: Plant damage value in the range of $1-‐10 million

1 Onsite: Poten.al restricted to injuries requiring no more than first aid. Offsite: Odor or noise complaint Environment: Contained release with local impact Property: Plant damage value in the range of $0.1 to 1 million


Qualitative Criteria / Typical Scenario

4 • Initiating event or failure

• Hose leaks/ruptures 3 • One level of protection

• Piping leaks 2 • Two levels of protection

• Full-bore failures of small process lines or fittings

1 • Three levels of protection • Tank/process vessel failures


Consequence Frequency

1 2 3 4

4 IV II I I

3 IV III II I 2 IV IV III II 1 IV IV IV III

Source: CCPS Guidelines for Hazard Evaluation Procedures, Second Edition

I Unacceptable (Should be mitigated with engineering and/or administrative controls to a risk ranking of III or less within a specified period e.g. 6 months) II Undesirable (Should be mitigated with engineering and/or administrative controls to a risk ranking of III or less within a specified period e.g.12 months) III Acceptable with control (Should be verified that procedures or controls are in place IV Acceptable As Is


Risk Mitigation •  Risk Level A : Risk mitigation required to risk level C or D •  Risk Level B : Risk mitigation required to risk level C or D •  Risk Level C : Risk mitigation to risk level D is optional •  Risk Level D : No further risk mitigation required


● Risk acceptance criteria: Criteria used as a basis for decisions about acceptable risk.

● Example of simple Risk Acceptance Criteria: –  All avoidable risks should be avoided. –  Risks should be reduced wherever practicable. –  The effects of events should be contained within the

site boundary. –  Further development should not pose any

incremental risk. ● Acceptable risk: Risk that is accepted in a given

context based on the current values of society and in the enterprise.


●  Risk acceptance is basically a question of the benefits you hope to receive from accepting a risk.

●  Some people seem to accept a very high risk voluntarily if the benefit they receive is very high to them.

●  An industrial worker may, for example, accept the risk from the plant that employs her because this activity provides her income.

●  Her neighbor, on the other hand, may find that the group (societal) risk from the same plant is totally unacceptable, as she receives no direct benefit from its operations.

●  Who, then is the legitimate decision-maker?


●  Tolerability refers to the willingness to live with a risk so as to secure some certain benefits and in the confidence that it will be properly controlled.

●  To tolerate a risk means that we do not regard it as negligible or something we might ignore, but rather as something we need to keep under review and reduce still further if and as we can.

●  For a risk to be acceptable ●  on the other hand means that for purposes of life or

work, we are prepared to take it pretty well as it is.


●  Unacceptable level of risk: unacceptable except in extraordinary circumstances (such as wartime), whatever their benefits. Activities causing such risk would be prohibited, or would have to reduce the risk whatever the cost.

●  Tolerable level of risk: tolerated in order to secure certain benefits. In this region, the risk is kept as low as reasonably practicable (ALARP), by adopting reduction measures unless their burden (in terms of cost, effort, or time) is grossly disproportionate to the reduction of risk they offer.

●  Broadly acceptable level of risk: the risk level is generally regarded as insignificant. Further actions to reduce the risk are not normally required.


INTOLERABLE LEVEL (Risk cannot be justified on any ground)

TOLERABLE only if risk reduction is impracticable or if its cost is grossly disproportionate to the improvement gained

TOLERABLE if cost of reduction would exceed the improvement gained

BROADLY ACCEPTABLE REGION

THE ALARP REGION (Risk is undertaken if benefited

is desired)

1 X 10-6 per year (residential) 1 X 10-5 per year (industrial)

1 X 10-3 per year (workers)

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“Reasonably practicable is a narrower term than “physically possible” and implies that a computation must be made in which the quantum of risk is placed in one scale and the sacrifice, whether in money, time or trouble, involved in the measures necessary to avert the risk is placed in the other; and that, if it be shown that there is a gross disproportion between them, the risk being insignificant in relation to the sacrifice, the person upon whom the duty is laid discharges the burden of proving that compliance was not reasonably practicable”

Edward Vs National Coal Board [1949] (British Court)

Risk Sacrifice (time, money, trouble)


● LSIR is used as a measure of individual risk

–  This means that the risk is not influenced by population

● Residential receptors: 1 x 10-6 fatalities per year

●  Industrial Receptors: 1 x 10-5 fatalities per year

● Voluntary risks:: 1 x 10-3 fatalities per year

1 x 10-3 1 x 10-6

1 x 10-5 Residential area

Proposed refinery

Industrial area


●  ALARA is an acronym for "as low as reasonably achievable", which is the risk acceptability framework in the Netherlands.

●  The ALARA principle is conceptually similar to ALARP, but does not include any region of broad acceptability.

●  Until 1993, the region of negligible risk was part of the Dutch policy. Subsequently, it has been abandoned on the grounds that all risks should be reduced as long as it is reasonable (Bottelberghs, 2000).

●  ALARA has, however, gained a somewhat different interpretation in practice.

●  According to Ale (2005), it is common practice in the Netherlands to focus on complying with the upper limit rather than evaluating the reasonable practicality of further action.

●  The unacceptable region in ALARA is, on the other hand, generally stricter than the one in ALARP, and the risk levels usually end up in the same range.


●  GAMAB is an acronym of the French expression globalement au moins aussi hon, which means "globally at least as good."

●  The principle assumes that an acceptable solution already exists and that any new development should be at least as good as the existing solutions.

●  The expression globalement (in total) is important here, because it provides room for trade-offs. An individual aspect may therefore be worsened if it is overcompensated by an improvement elsewhere.

●  The GAMAB principle has been used in decision-making related to transportation systems in France, where new systems are required to offer a total risk level that is globally as low as that of any existing equivalent system.


●  MEM is an acronym for minimum endogenous mortality, which is a German principle that uses the probability of dying of natural causes as a reference level for risk acceptability.

●  The principle requires that new or modified technological systems must not cause a significant increase in the IRPA of any person (Schabe, 2001).

●  MEM is based on the fact that death rates vary with age and the assumption that a portion of each death rate is caused by technological systems (Nordland, 2001).


●  In this life, there is no such thing as zero risk, there is always some risks associated with any activity

● At level should we tolerate these risks ?

● Two types of Risks

•  Voluntary Risks

•  e.g. driving or riding in an automobile, and working in an industrial facility.

•  Involuntary Risks

•  e.g. exposure to lighting, disease, typhoons and persons in residential or recreational areas near the industrial facilities.


Voluntary Risks

Involuntary Risks

10,000

1,000

100

10

10

5,000

2,000

800

170

50

10

3

Smoking 1 pack of cigarettes per day Riding a motorcycle

Fighting a fire

Driving a car

Pedestrian hit by a car Taking X Ray for diagnosis

Death by Lightning or tornadoes


Voluntary Risks Involuntary Risks

Activity

Risk fatalities (death) per

person per yr (x106)

Activity

Risk fatalities (death) per

person per yr (x106)

Smoking (20 cigarettes/day) Motor cycling Car racing Car driving Rock climbing Football

5000

2000 1200 170 40 20

Influenza Leukemia Run over by road vehicle (UK) Run over by road vehicle (USA) Floods (USA) Storms (USA) Lightning (USA) Falling aircraft (USA) Falling aircraft (UK)

200 80 60

50

2.2 0.8 0.1 0.1

0.02

50


●  Societal risks (Ball and Floyd, 1998) discusses societal risk and different reg- ulatory practices for establishing FN criterion lines.

●  Acceptahle Risk (Fischhoff et aI., 1981) is a pioneering book on risk acceptability, which evaluates three principal approaches to acceptable risk problems: expert judgment, bootstrapping (accepting what has been accepted in the past), and formal analysis.

●  Reducing Risks, Protecting People: HSE's Decision-Making Process ●  (HSE, 200 Ib) presents the ALARP framework in the decision-making context of the UK HSE. ●  The Tolerability ofRiskfrom Nuclear Power Stations (HSE, 1992) explains the principal thinking

behind HSE's approach to risk acceptability. ●  Foundations and fallacies of risk acceptance criteria (Johansen, 201Oa) was written in parallel

with this book and offers more principal discussions on the use of risk acceptance criteria. ●  Risk and emergency preparedness analysis (NORSOK z-o13, 2010) provides a nice overview of

the pros and cons of various risk indicators. ●  Risk evaluation criteria (Skjong et aI., 2007) presents a comprehenSive review of risk indicators

and evaluation criteria in the marine industry. ●  OffshoreRiskAssessment: Principles,ModelingandApplicationofQRAStud- ies (Vinnem, 2007)

discusses trends and risk indicators for harm to people and the environment in offshore industries.

arshad ahmad [email protected] 1 global 1 · localized individual risk (lira): the probability that an...

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