What is Tolerable Risk?
Introduction
It is often stated that, when conducting risk assessments, that suitable and sufficient controls should be implemented to ensure that the residual risk is reduced to a tolerable level so work can be carried out without serious consequences. In this article we are trying to explain what is meant by tolerable risk in so far as it refers to safety and health issues at a worksite.
Discussion
It should be noted that tolerable risk is defined as being risk that is bearable in a specific context based on the current values of society. It follows that, over time, protective measures may have led to an acceptance of the residual risk (resulting from identified hazards) that may need to be reviewed to determine if residual risk levels are at tolerable levels. This is because tolerability is not a static entity.
Some organizations use a cost benefit analysis to justify when a risk is tolerable, there is a flaw in this process. Utilitarianism thinking closely align with cost-benefit analysis where most of the cost-benefit analyses gives the initiator the costs and benefits, and not the costs and benefits to everybody. In addition, it will be a brave person that will put a monetary cost to an employee’s life.
In a graphic adapted from a publication by Richard J.T. Klein about acceptable, tolerable, and intolerable risks in relation to adaptation limits repeated below one can see the two limits he defined.
When determining these limits, it should be noted that the area of tolerability as defined in this graphic is not fixed or linear but can vary from site to site as well as over time at a site. This variability makes the determination of tolerability even more complex.
Legislative standards establish minimum levels of performance that is not fixed on a consequential outcome, often leaving some level of risk. If the residual risk is high (relative to the affected site’s risk tolerance) after applying controls established by legislation, the affected site may have to implement controls beyond the requirements of the legislation to further decrease the probability and/or resulting severity of an adverse occurrence. Some laws have general duty clauses such as “take every precaution reasonable in the circumstances for the protection of a worker” to address these types of gaps. It is not always possible for employers to write safety procedure for every job task that may take place in a workplace.
Therefore, site specific occupational health and safety standards in essence establish minimum tolerable risk for the subject activity or exposure as defined by the specific employer. If a hazard is controlled in accordance with the appropriate employer’s standard, then the risk of the adverse event or outcome should be to the level deemed tolerable by the specific employer.
The introduction of the notion that only "significant risk" should be treated, further increased the difficulty to understand risk assessment.
Traditionally, significance is seen to be statistically based, however, the Inspectorate deemed it impractical and unnecessary to establish significance of risk by means of statistical trending methods. As there is already effective legislation in place, accident statistics will not show the full potential of the hazard but will only reflect what has happened in the past and the result of the residual risk combined with the accidents resulting from non-compliance. Accident statistics are only an indication of the gaps in existing legislation. It is for this reason that another approach is required.
Several authors have identified different means of establishing significance. They are, however in agreement that three criteria must be satisfied before a causal association can be inferred between exposure and health or safety related incidence.
These criteria can be summarised as follows:
There is no identified bias that could explain the association.
The possibility of confounding has been considered and ruled out as explaining the association.
The association is unlikely to be due to chance.
It should be noted that in general, legislation does not require statistical significance between a hazard and a specific type of accident before the hazard could be deemed to be a significant hazard. This could be triggered by any one of several things, including social outcries and emotional impacts by a single accident.
Guidelines
To this end the following guidelines have been developed in respect of determining the causal relationships.
A causal interpretation is enhanced for accidents to the extent that they meet the criteria described below. None of the criteria is conclusive by itself and the only criterion that is essential is the passing relationship.
Passing relationship:
The occurrence of accidents requires certain critical elements to be present, and while some of the critical elements may have been absent before and after the occurrence of the accident, the existence of such critical elements is generally acknowledged. Thus, the accident must occur within a timeframe when all the critical elements were present. This feature must be present if causality is to be considered.
Consistency:
Associations occur in several independent investigations of similar exposure in different populations, or associations occur consistently for different subgroups in the same investigation. This feature usually constitutes strong evidence for a causal interpretation when the same bias or confounding is not also duplicated across the investigations.
Magnitude of the association:
A causal relationship is more credible when the risk estimate is large and precise (narrow confidence intervals).
Hazard gradient:
The risk ratio (i.e. the ratio of the risk of disease or death among the exposed to the risk of the unexposed) increases with increasing exposure. A strong response relationship across several categories of exposure, and duration is supportive for causality given that confounding is unlikely to be correlated with exposure. The absence of a hazard response relationship, however, is not by itself evidence against a causal relationship.
Specificity of the association:
The likelihood of a causal interpretation is increased if an exposure to a specific hazard produces a specific effect or if a given effect results from a unique exposure.
Plausibility:
The association makes sense in terms of existing knowledge. Information is considered from historic accident statistics, incidents reported and the relationship analysis of the influence that the hazard had on events in the past.
Coherence:
The cause-and-effect interpretation is in logical agreement with what is known about the hazard as well as the controls in place to alleviate the risk, i.e., the entire body of knowledge about the hazard.
Most occupational risks are well documented and the potential for disasters have long been a well-known fact. If the above criteria are utilised the confusion to determine significant risks should be largely eliminated.
Conclusion
Based on the above discussion it should be clear to the reader that determining tolerability is not an easy task that can be left to individuals to manage when conducting their tasks. It is considered important and complex enough for each site to have the board of director risk committee’s signoff on what is deems to be tolerable safety risk.
The COVID-19 pandemic has proven this, many organizations have been caught off guard without continuity plans and did not think that the impact from the spread of virus was going to shut down the world economy.
It would be prudent for employers to revisit its risk tolerance to see if changes in their work activities could increase the livelihood of a consequence to occur and re-evaluate based on changes, benchmarking with external incidents and complement your team with subject matter experts and risk management professionals. Once this is done, you should mandate them to ask, and answer the question whether your organizations have adequate safeguards that will keep your risks from becoming intolerable risks and business resilience plans that can be implemented to keep risk from increasing to the point of intolerability.
Should you need assistance with any of the aspects discussed in this article, please do not hesitate to contact the authors directly.
Please feel free to contact us at: drcmarx@gmail.com or roger.belair@onsitehse.com
If you would like to read our previous articles, the please click on the following link:
Risk-Based-Decision-Making: https://www.linkedin.com/pulse/importance-risk-based-decision-making-safety-risk-management-marx/
Hazard Identification Risk Assessment Process: https://www.linkedin.com/pulse/hazard-identification-risk-assessment-hira-process-carl-marx/
Identifying Hazards: https://www.linkedin.com/pulse/identifying-hazards-carl-marx
Risk Response Categories to Consider: https://www.linkedin.com/pulse/risk-response-categories-consider-carl-marx/
