CLAIMS JUDICIAL PROCEEDINGS Like- lihood Seve- rity Risk Like- lihood Seve- rity Risk Like- lihood Seve- rity Risk Like- lihood Seve- rity Risk H1 0.1 2 0.2 I1 0 2 0 C1 0 2 0 J1 0 2 0 H2 0.2 3 0.6 I2 1 3 3 C2 1 3 3 J2 0 3 0 H3 0.05 50 2.5 I3 0 50 0 C3 0 50 0 J3 0 50 0 H4 0.3 2 0.6 I4 2 2 4 C4 1 2 2 J4 1 2 2 H5 0.65 13 8.45 I5 0 13 0 C5 0 13 0 J5 0 13 0 H6 0.025 260 6.5 I6 0 260 0 C6 0 260 0 J6 0 260 0 H7 0.001 1500 1.5 I7 0 1500 0 C7 0 1500 0 J7 0 1500 0 H8 0.45 0.5 0.23 I8 0 0.5 0 C8 0 0.5 0 J8 0 0.5 0 H9 0.01 6 0.06 I9 0 6 0 C9 0 6 0 J9 0 6 0 H10 0.5 60 30 I10 1 45 45 C10 1 45 45 J10 1 45 45 H11 0.005 100 0.5 I11 0 100 0 C11 0 100 0 J11 0 100 0 : : : : Hi 0.003 1 0 Ij 0 0 0 Cj 0 0 0 Jj 0 0 0 ∑Hi 51.1 ∑Ij 52 ∑Cj 50 ∑Jj 47 Event Horizon
<<<<<<Pre-Event Control / Post - Event Management >>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Concept Hazard Register
The above table suggests why such an approach could be considered. Over any period of time, most hazards will not result in incidents and of the incidents that do occur only a few will give rise to claims. Most of the costs will manifest in those claims that make it to court. This ought to be a small subset of the set of all hazards and incidents. However, there are obviously other dimensions to managing risk like this. Unless one is clairvoyant it is not possible to know which hazards definitely will lead to court cases and which ones will not. So only if a company was both naive and immoral would it attempt to manage risk by trying to identify and manage only those hazards which it thought might lead to incidents that could end up giving rise to prosecution or a common law claim.
6.2 Individual Risk Criteria
If a single severity of outcome is being considered then very often probability criteria can be used as the basis to benchmark risk. Many countries in the world maintain databases on causes of death to their citizens. These can be analysed. A typical result is shown on the following page.
These tables are basically a statement of what a particular community seems to have historically accepted as ‘reasonable’. That is, what we as a society are willing to live with. Nuclear authorities usually undertake such studies. They are very interested in where nuclear risk is perceived to lie. The numbers for the NSW figures were prepared by ANSTO (Australian Nuclear Science and Technology Organisation).
From such lists various authorities suggest acceptable frequencies of death for individuals in critical exposed groups. These numbers are in chances per million per year. That is, the chances, on
average, of being struck and killed by lightning in NSW is one in ten million per year or alternatively, for an individual, once in every ten million years.
Voluntary Risks (average to those who take the risk)
Chances of fatality per million person years Smoking (20 cigarettes/day)
1. all effects 2. all cancers 3. lung cancers
Drinking alcohol (average for all drinkers) - all effects
- alcoholism and alcoholic cirrhosis Swimming
Playing rugby football Owning firearms 5000 2000 1000 380 115 50 30 30
Transportation Risks (average to travellers) Travelling by motor vehicle
Travelling by train
Travelling by aeroplane accidents
145 30 10
Risks averaged over the whole population Cancers from all causes
total lung
Air pollution from burning coal to generate electricity Being at home-accidents at home
Accident falls
Pedestrians being struck by motor vehicles Homicide
Accidental Poisoning • total
• venomous animals and plants Fires and accidental burns
Electrocution (non-industrial) Falling objects
Therapeutic use of drugs
Cataclysmic storms and storm floods Lightning Strikes Meteorite strikes 1800 380 0.07-300 110 60 35 20 18 0.1 10 3 3 2 0.2 0.1 0.001 Risks to Individuals in New South Wales
Such data can also be represented in a triangle type diagram, sometimes referred to as "the dagger diagram".
The two key levels seem to lie around road death statistics and the chances of being struck by lightning. In simple terms, it seems that if we believe something is more dangerous than driving a car then the risk is unacceptable (about one chance in 10,000 per year), but that if it about as likely as being struck by lightning (about one chance in 10 million per year), then it is probably so low that we don't expect anyone to do anything about it. In the range between these two figures cost benefit studies to reduce the risk to as low as reasonably practicable is appropriate
Negligible risk Intolerable; risk cannot be justified except in
extraordinary circumstances
Acceptable
Limit for WA EPA
Objective for NSW DoP Risk Categories I II III IV V
Car Accident Death Rate Typical Quantification
Values
Lightning Strike Death Rate Objective for Vic VWA Levels of Risk Acceptability
Trivial risk Undesirable; tolerable only if reduction is impractical or if cost is grossly disproportionate to the improvement gained
Tolerable if the cost of reduction would exceed the improvement gained 10 per year-7 10 per year-6 10 per year-5 10 per year-4 Broadly Acceptable
Risk Levels for Individuals in a Critically Exposed Group Diagram (without quantification) appears in IEC 61508 as figure B1
Many organisations are now emphasising the risk criteria of tolerance rather than acceptance. To tolerate risk means that risk is not regarded as negligible, meaning that it can be ignored. Rather, it must be kept under review and reduced still further to the negligible level if and when this becomes practical. The key element is the process by which it is demonstrated that all practicable measures have been taken to reduce risk levels to a minimum.
The Victorian WorkCover Authority, the NSW Department of Planning and the Western Australian Environmental Protection Authority (EPA) have defined individual risk levels. Other Australian States tend to utilise one or other of these criteria when assessing individual and/or societal risk. A summary of criteria used in Australia and New Zealand is described in Chapter 13, Process Industry.
For example, the NSW Department of Planning has published an advisory paper "Risk Criteria for Land Use Safety Planning" (June 1992) that outlines the criteria by which the acceptability of risks associated with potentially hazardous developments will be assessed.
The table below summaries the criteria for the individual fatality risk for new installations.
Risk Level Land Use
0.5 x 10-6 pa Hospitals, schools, child care facilities, old age housing 1.0 x 10-6 pa Residential, hotels, motels, tourist resorts
5 x 10-6 pa Commercial developments including retail centres, offices and entertainment centres
10 x 10-6 pa Sporting complexes and active open spaces 50 x 10-6 pa Industrial
Individual Fatality Risk-New Installations 6.3 Societal Risk Criteria
As the severity of the event increases, we appear to become more risk averse. Particularly, once the death threshold is passed, it appears the community has a much greater aversion to multiple fatality incidents. Authors such as Wiggins (1984) in the USA have noted that the dollars Congress spends per life saved for a coalmine disaster or aircraft collision is much higher than the dollars spent to save a life on the road.
In many countries this seems to amount to a one hundred-fold decrease in the likelihood of the event for a ten-fold increase in the severity of the consequence measured in fatalities. This is shown in the Netherlands criteria below. Societal risk analysis combines the consequence and likelihood information with population information. This is presented as a F-N plot, which indicates the cumulative frequency (F) of killing 'n' or more people (N).
Netherland Unacceptable Limit Netherland Acceptable Limit 1 10 100 1000 10 10 10 10 10-3 -4 -5 -6 -7 -8 10 Number of Fatalities (N) Frequency of N or more fatalities per year ALARP (As low as reasonbly practicable)
Societal Risk Criteria
For example, societal risk criteria for public safety relating to hazardous industries have not been formally established and publicised in Victoria. There is currently a set of draft criteria issued by the Victorian WorkCover Authority (VWA), which is used by Government Authorities involved in Land Use Planning. This criterion was used as part of the Technica Ltd, “Risk Sensitivity Analysis for the Altona Petrochemical Complex and Environs”, October 1997.
The document establishes criteria for societal risk in the form of a log-log F-N plot that results in two parallel lines defining three zones:
a) above the acceptable limit the societal risk level is not tolerable
b) between the acceptable and negligible limits the societal risk level is acceptable but if the
perceived benefits gained by the activity are not high enough, some risk reducing measures may be required. Risk should be "as low as reasonably practicable" (ALARP).
c) below the negligible limit, the societal risk level is acceptable, regardless of the perceived value of the activity. 1 10 100 1000 10 10 10 10 10-2 -3 -4 -5 -6 -7 10 Risk Unacceptable Risk Acceptable but remedial measures desirable Risk Negligible Number of Fatalities (N) Frequency of N or more fatalities per year
Victorian Societal Risk Criteria 6.4 Environmental Risk Criteria
Unlike OH&S risk assessment in which all evaluations have a common denominator, namely “human exposure”, environmental risk assessment has a much broader and complex scope with a substantial increase in the number of uncertainty characteristics.
6.4.1 Wright's Criteria
Wright (1993) describes several factors which need to be recognised. * ecosystems are complex, open and dynamic
* the time-scale to cause measurable impact or recovery from impacts may be longer than human life
* persistent materials which are bio-available, and have the potential to bio-accumulate should be avoided, discharge will cause irreversible net change
* the relative scale of the environmental impact must be considered in all environmental dimensions (spatial, temporal etc)
* the ecosystem has inherent or built-in variability and recoverability * cause and effect relationships are often difficult to measure * interdependency exists between different eco-sub-systems
There is also the problem of synergistic effects. This means, for example, that two chemicals which are individually inert in the environment, interact to cause damage.
Wright also suggests that it is possible to calculate the likelihood and size of accidental or intermittent releases and then make a judgement on what the consequences of such releases would be. The table of consequences is shown below:
Consequence Type
Description
Catastrophic Irreversible alteration to one or more eco-systems or several component levels. Effects can be transmitted, can accumulate.
Loss of sustainability of most resources. Life cycle of species impaired. No recovery. Area affected 100 km2
Very Serious Alteration to one or more eco-systems or component levels, but not irreversible. Effects can be transmitted, can accumulate. Loss of sustainability of selected resources. Recovery in 50 years. Area affected 50 km2.
Serious Alternation/disturbance of a component of an eco-system. Effects not transmitted, not accumulating or impairment. Loss of resources but sustainability unaffected. Recovery in 10 years.
Moderate Temporary alteration or disturbance beyond natural viability. Effects confined < 5000 m2, not accumulating. Resources temporarily affected. Recovery < 5 years.
Not detectable Alteration or disturbance within natural viability. Effects not transmitted, not accumulating. Resources not impaired.
Environmental Consequences In the context of a risk diagram: