Safety and health risk assessment is a combination of likelihood and severity of the hazard. Different definitions and statement has been used for likelihood and severity. This paper attempts to consolidate by expanding severity and likelihood codes or statements for a realistic safety and health risk assessments. Likelihood in expanded version includes probability, levels of controls, behaviour, culture and attitudes, likely of occurrence, exposure levels, morale, and number of people likely to be affected, and training. Severity in broader sense includes the degree of injury to people and property (which can also mean near miss).
Codes; Hazard; Risk Assessment; Safety; Health
The risk associated with any work activity depends on the severity of an accident or ill health that may occur, and the likelihood of its occurrence the safety and health risk associated with any work activity depends on the severity of an accident or ill health that may occur, and the likelihood of its occurrence .
Risk depends on all three factors: Hazard, vulnerability, and exposure. Risk is the estimated impact that a hazard would have on people, services, facilities, and structures in a community . It refers to the likelihood of a hazard event resulting in an adverse condition that causes injury or damage all safety and health risks at work can be controlled, and all accidents or ill health can be prevented. Safety and Health (S and H) risk management is a process by which the organization’s management assesses the risks, determines the control measures, and takes appropriate actions to reduce such risks. Anything that has the potential to cause harm is generally defined as hazard.
The combination of the likelihood of an occurrence of a hazardous event or exposure(s) and severity of injury or ill health that can be caused by the event or exposure(s) is termed as risk. Different models use different definitions for severity and likelihood, which are highlighted below .
Risk Assessment Code (RAC) a hazard number ranking system from 1 (the highest level of risk) to 5 (the lowest level of risk). Risk Assessment Matrix (RAM)–A tool used to assign RACs. Likelihood Code (A through D) indicating the probability or chance of an event actually occurring is shown in Table 1 .
|A||Frequent||Immediate danger to the health and safety of the public, staff, resources, or property; occurs frequently or continuously|
|B||Likely||Probably will occur in time if not corrected, or probably will occur one or more times during the life of the system|
|C||Occasional||Possible to occur in time if not corrected|
|D||Rarely||Unlikely to occur, may assume exposure will not occur|
Table 1: Likelihood code.
Consequence Code–Code (I through IV) indicating the severity of consequence resulting from exposure to a hazard is shown in Table 2 .
|I||Catastrophic||Imminent and immediate danger of death or permanent disability, chronic or irreversible illness, major property or resource damage.|
|II||Critical||Permanent partial disability, temporary total disability greater than 3 months, significant property or resource damage|
|III||Significant||Hospitalized minor injury, reversible illness, period of disability of 3 months or less, loss or restricted workday accident, compensable injury or illness, minor property or resource damage|
|IV||Minor||First aid or minor medical treatment. Presents minimal threat to human safety and health, property, or resources, but is still in violation of a standard|
Table 2: Severity code.
The SEP model defines Risk (R)=Severity × Probability × Exposure or R=S × P × E. Here a third dimension of Exposure is given. Following Table 3 summarises the SEP model .
|1||none or slight||Impossible or remote under normal conditions||None or below average|
|2||Minimal||Unlikely under normal conditions||Average|
|3||Significant||50/50 chance||Above average|
|4||Major||Greater than 50% chance||Great|
|5||Catastrophic||Very likely exposure||-|
Table 3: SEP model.
Other model considers possible harm to employees, contractors, members of the public, those using products and services and anyone else affected by the activity, such as neighbours other consideration is given for persons who could be affected in different groups, such as young or inexperienced workers, pregnant workers, workers with a disability, migrant workers or ageing workers .
As safety and health is beyond traditional risk, it is important to be aware that human failure is not random understanding why errors occur and the different factors which make them worse will help you develop more effective controls. There are two main types of human failure: Errors (Some errors are slips or lapses, often "actions that were not as planned" or unintended actions, other errors are mistakes or errors of judgement or decision-making where the "intended actions are wrong" i.e. where we do the wrong thing believing it to be right) and violations (non-compliances, circumventions, shortcuts and workarounds) differ from the above in that they are intentional but usually well-meaning failures where the person deliberately does not carry out the procedure correctly).
A violation is a deliberate deviation from a rule or procedure .
A three-dimensional method, utilizes the traditional likelihood (Y-axis) and severity (X-axis), while adding a new, third dimension, as the Z-axis, and referred to as the level of control . One of the step in risk assessment is to consider as who might be harmed and how, such as how your employees could be harmed by business activities or external factors .
Translating strength of controls into likelihood, the problem remains of associating likelihood with strength of potential controls. In system concept development and in early decisions about the development process (e.g., where to invest resources), an estimate of the potential strength of designed controls for the scenarios would be used to assess likelihood. Various strategies might be used to rank the strength of potential controls as shown in Table 4 .
|Ranking strength of controls||Description|
|1||The causal factor can be eliminated through design and high assurance|
|2||The occurrence of the causal factor can be reduced or controlled through system design|
|3||The causal factor can be detected and mitigated if it does occur through system design or through operational procedures|
|4||The only potential controls involve training and procedures.|
Table 4: Strength of controls.
A guide to severity rating described as shown in Table 5 .
|1||Catastrophic Death||Fatal diseases or multiple major injuries|
|2||Major||Serious injuries or life-threatening occupational diseases (includes amputations, major fractures, multiple injuries, occupational cancers, acute poisoning, disabilities and deafness).|
|3||Moderate||Injury or ill-health requiring medical treatment (includes lacerations, burns, sprains, minor fractures, dermatitis and work-related upper limb disorders)|
|4||Minor||Injury or ill-health requiring first-aid only (includes minor cuts and bruises, irritation, ill-health with temporary discomfort).|
Table 5: Severity rating.
A guide to Likelihood rating described as shown in Table 6 .
|1||Almost Certain||Continual or repeating experience|
|3||Occasional||Possible or known to occur|
|4||Remote||Not likely to occur under normal circumstances|
|5||Rare||Not expected to occur but still possible|
Table 6: Likelihood rating.
According to McGregor, theory X person assumes the work is inherently distasteful to most people, and they will attempt to avoid work whenever possible and theory Y presents an optimistic view of the employees’ nature and behaviour at work. Thus theory Y person is likely to cause an incident, while theory X person is more likely to cause incidents .
Work attitude not only affects how well people do their job, but it also affects how safe they are when doing it. Positive people usually perform better in the workplace because they maintain an open mind and consider the outcome of their behavior . Negative people, on the other hand, complain about everything, including having to practice safety. A negative work attitude can lead to unsafe work habits and accidents. Negative workplace behaviour, such as workplace bullying, is an important work-related psychosocial hazard with the potential to contribute to employee ill health.
There is a need to expand the statements used in severity and likelihood so as to make a comprehensive risk assessments.
Key objective of this paper is to have an inclusive definition for severity and likelihood for assessing safety and health risk.
3 step approach
Different models have varied definitions for severity and likelihood for a safety and health risk assessment. Following 3 steps are adopted for this model (Figure 1).
Figure 1: 3 step process for risk assessment.
Step 1: Summarizing the broad parameters used for severity and probability/likelihood are:
• Severity-Injuries to people and property damage.
• Likelihood or probability level of controls, likely to occur, behaviour/culture, exposure levels, morale, attitude and number of people likely to be affected, and training. Level of controls includes training, well written procedures, supervision and instructions
Step 2: Creating a severity and likelihood codes/rankings. For this exercise, 5 × 5 matrixes are adopted. This step is to have a severity and likelihood table. It identifies the broad definitions and statement that can be used for likelihood and severity respectively (Tables 7 and 8).
|Attributes||Rare (1)||Remote (2)||Occasional (3)||Frequent (4)||Almost Certain (5)|
|Statement||Not expected to occur but still possible, Impossible or remote under normal conditions||Not likely to occur under normal circumstances||Possible or known to occur, 50/50 chance||Common occurrence, Greater than 50% chance||Continual or repeating experience, Very likely chance|
|Level of existing controls||Great engineering controls and good supervision, instruction and training||Above average controls||Average controls with good supervision, instruction, training||The only potential controls involve training and procedures.||None or no controls The only potential controls having procedures|
|Morale||Extremely high||High morale||Moderate morale||Low morale||Very low morale|
|Culture||Excellent organisation culture||High positive organisation culture||Moderate positive organisation culture||Low or negative organisation culture||Very low organisation culture|
|Behaviour||100% theory Y personnel||>50% theory Y personnel||25-50% theory Y personnel||>50% theory X personnel||100% theory X personnel|
|Exposure how many people are likely to be exposed to the hazard?||One or small group||Many people||One or small group and specific groups vulnerable than others||Many and vulnerable groups such as people with mental stress/pre- existing medical condition||Many and specific groups more vulnerable people with disabilities, pregnant women|
|Casual factors||The causal factor can be eliminated through design and high assurance||The occurrence of the causal factor can be reduced or controlled through system design||The causal factor can be detected and mitigated if it does occur through system design||The causal factor is difficult to be detected||The causal factor cannot be detected|
|Probability of occurrence||Very rarely to occur||Possible to occur in time if not corrected||Possible to occur one or more times during the life of the system||Possible to occur many more times||Possible to occur frequently|
Note: (1), (2), (3), (4), (5) refers to risk matrix.
Table 7: Likelihood statements.
|Attributes||None or slight (1)||Minimal (2)||Significant (3)||Major/Critical (4)||Catastrophe (5)|
|Statement||Negligible injury||Mild injury which can be treated in house||Treatment by external such as hospital||Treatment requiring hospitalization||Fatality|
|Property Damage||No property damage||Mild property, or resources||Moderate property or resource damage||Significant property or resource damage||Major property or resource damage|
|Injury||Negligible injury||First aid or minor medical treatment. Presents minimal threat to human safety and health,||Hospitalized minor injury, reversible illness, period of disability of 3 months or less, loss or restricted workday accident, compensable injury or illness. Injury or ill- health requiring medical treatment (includes lacerations, burns, sprains, minor fractures, dermatitis and work- related upper limb disorders)||Permanent partial disability, temporary total disability greater than 3 months. Serious injuries or life- threatening occupational diseases (includes amputations, major fractures, multiple injuries, occupational cancers, acute poisoning, disabilities and deafness).||Imminent and immediate danger of death or permanent disability, chronic or irreversible illness. Fatal diseases or multiple major injuries|
|Reputation||No impact||Temporary impact to reputation||Mild reputation damage, still can be managed through public relations||Moderate impact to business||Serious impact, potentially leading to closure|
Note: (1), (2), (3), (4), (5) refers to risk matrix.
Table 8: Severity statements.
Step 3: Evaluate risk using the matrix (in numbers and words) are shown in Tables 9 and 10.
|Likelihood Severity||Rare (1)||Remote (2)||Occasional (3)||Frequent (4)||Almost Certain (5)|
Note: (1), (2), (3), (4), (5) refers to risk matrix.
Table 9: Example of a common 5 × 5 risk matrix with a mix of numeric and descriptive ratings .
|Likelihood Severity||Rare (1)||Unlikely (2)||Possible (3)||Likely (4)||Almost Certain (5)|
Note: (1), (2), (3), (4), (5), (A), (B), (C), (D), (E) refers to risk matrix.
Table 10: Example of a common 5 × 5 risk matrix with a mix of words and descriptive ratings .
Mathematically, Risk can be expressed as f (R)=f (L, S) …....……. (1)
Where R is Risk, L and S are Likelihood and Severity.
Expanding equation 1, we get
R=L × S ……………….. (2)
Risk is directly proportional to the product of likelihood and severity.
When risk has to be controlled or reduced, it should be noted that L and/or S has to be reduced. Traditional approaches to risk controls include the hierarchy of controls as shown below in Figure 2.
Figure 2: Hierarchy of controls.
Elimination and substitution, while most effective at reducing hazards, also tend to be the most difficult to implement in an existing process . Well-designed engineering controls can be highly effective in protecting workers and will typically be independent of worker interactions to provide this high level of protection. For an existing process, major changes in equipment and procedures may be required to eliminate or substitute for a hazard. These are examples of reducing severity. Administrative controls and PPE are frequently used with existing processes where hazards are not particularly well controlled. Administrative controls and PPE programs may be relatively inexpensive to establish but, over the long term, can be very costly to sustain. These methods for protecting workers have also proven to be less effective than other measures, requiring significant effort by the affected workers.
These are examples of reducing likelihood. Once the risk reduction strategy is identified, say to reduce L or S, Tables 7 and 8 may be used to determine, as which suitable control measures are reasonable and practical that can be applied.
When computing likelihood or severity statements/code, it should be evaluated against all possible attributes. In situations, where one of the attributes falls in different codes, highest code should be taken. For example, if morale of staff is very high, but there are no controls, likelihood should be taken as almost certain (5). Similarly, for severity.
There may be other attributes such as duration of exposure, which can be decided by the team conducting the risk assessments. This model is based on 5 × 5 matrix of risk assessment. Should anyone wish to use other matrix such as 3 × 3, statements or codes mentioned in Tables 7 and 8 have to be modified.
Any organisation’s responsibility is to ensure risk is eliminated or controlled to as reasonable as practical. The key to risk assessment is evaluating severity and likelihood of the hazard to occur. Having an inclusive definition for severity and likelihood, risk assessment will be more realistic and accurate. This model can be used when impact to environment is to be considered. This expanded definition can be used for other types of matrix.
Citation: Venkataraman N (2021) Safety and Health Risk Assessment Expanding Severity and Likelihood Codes. J Ergonomics. S5:001.
Received: 05-Oct-2021 Published: 26-Oct-2021, DOI: 10.35248/2165-7556.21.s5.001
Copyright: © 2021 Venkataraman N. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.