Accepted Risk-Based Safety Systems

INTERNATIONALLY ACCEPTED RISK-BASED SAFETY SYSTEMS 

There are numerous prominent international safety systems currently in use throughout the world. They include, inter alia  

National Occupational Safety Association (NOSA) Five-Star Safety System Safety Projects International (SPI) Five-Star Health and Safety Management System 

British Safety Council s Five-Star Health and Safety Audit System International Loss Control Institute s International Safety Rating System (ISRS) International Organization for Standardization (ISO) (environment, quality, etc.) 

British Standards Institute (BSI) Occupational Health and Safety Assessment Series (OHSAS) 

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INTERNATIONALLY ACCEPTED RISK-BASED SAFETY SYSTEMS... 

I was offered the opportunity to address the mine management during my visit, and a suitable seminar was arranged. The company s managing director also attended the seminar. After a short presentation and much discussion, the mine accepted the radical principles of the Five-Star Safety System, and for the first time in almost 70 years embarked on a risk-based, management-led, audit-based safety system. 

Let us comment on the case where a safety specification is not available. Generally speaking, the lawgiver demands that the hazards and risks of the system are acceptable for all stakeholders. He requires that new systems should use state-of-practice technologies for achieving acceptable risks. Based on these principles often safety requirements are specified in standards. If standards are not available, necessary risk reduction measures can be derived from system analysis and quantitative or quahtative hazard and risk analysis (see e.g. lEC 61508). The hazard and risk analysis should consider all potential hazards, for instance, all stakeholders brainstorm on the basis of sufficient system knowledge. 

A safety argument must explain how the available evidence supports the overall claim of acceptable safety. Best practice, risk-based, safety arguments decompose this claim into arguments that justify the acceptability of the risk posed by identified system hazards. For each hazard, the argument states what adequately addressed means for that hazard and then identifies the evidence supporting the conclusion. This structure explains the purpose of each piece of evidence. 

Based on these differences, the use of RfDs for hazardous chemicals that induce deterministic effects to define acceptable exposures of the public often may be considerably more conservative (provide a substantially larger margin of safety) than the dose limits for radiation induced deterministic effects. The likely degree of conservatism embodied in RfDs has important implications for establishing limits on allowable exposures to substances causing deterministic effects for the purpose of developing a risk-based waste classification system. Dose limits for deterministic effects for radiation should not be important in classifying waste (see Section 3.2.2.1). 

In many respects, the foundations and framework of the proposed risk-based hazardous waste classification system and the recommended approaches to implementation are intended to be neutral in regard to the degree of conservatism in protecting public health. With respect to calculations of risk or dose in the numerator of the risk index, important examples include (1) the recommendation that best estimates (MLEs) of probability coefficients for stochastic responses should be used for all substances that cause stochastic responses in classifying waste, rather than upper bounds (UCLs) as normally used in risk assessments for chemicals that induce stochastic effects, and (2) the recommended approach to estimating threshold doses of substances that induce deterministic effects in humans based on lower confidence limits of benchmark doses obtained from studies in humans or animals. Similarly, NCRP believes that the allowable (negligible or acceptable) risks or doses in the denominator of the risk index should be consistent with values used in health protection of the public in other routine exposure situations. NCRP does not believe that the allowable risks or doses assumed for purposes of waste classification should include margins of safety that are not applied in other situations. 

The design of safety systems supported by PSA provides efficient designs at a lower cost than those based solely on engineering criteria, guaranteeing a priori an adequate level of safety with a predetermined risk acceptance. It is also a useful tool for appropriate location of isolation valves. 

To be in a position to anticipate hazards, one must be involved in the design process. To effectively participate in the design process, the safety professional must be skilled in hazard analysis and risk assessment techniques. Influencing the design process and using hazard analysis and risk assessment techniques to achieve acceptable risk levels are the bases upon which system safety is built. 

In this paper methods are critically reviewed, developed and explored on how to deal with this problem and how to include them in a risk analysis of coastal-and fluvial floods. An investigation of accepted risks in the coastal and fluvial flood-prone areas is made to answer the question if safe is safe enough and to define the acceptable risk levels. A risk-based approach in defining optimal safety levels of water defence system is developed. Application is made to define the optimal safety standmd for a case of coastal flood defences in Nam Dinh province, Vietnam. 

Systemic Socio-Technical Causation Model for Hazards-Related Incidents At least 25 incident causation models are referenced in safety literature. They present a great diversity of thinking. None of those models have achieved anything close to universal acceptance. Yet, safety professionals are obligated to have the advice they give be effective as clients take action to avoid, eliminate, or control hazards and to achieve acceptable risk levels. That advice must be based on a sound and studied thought process that takes into consideration the reality of the sources of hazards. This author builds a case in support of what he proposes for a systemic sociotechnical causation model for hazards-related incidents. 

Replacing the term tolerable risk with acceptable risk in BS OHS AS 18001 by an organization as influential as the British Standards Institution is noteworthy. In some parts of the world, because of requirements in contract bid situations, companies are required to show that their safety management systems are certified. BS OHSAS 18001 is often the base of such certification. This modification made by the British Standards Institution indicates that the goal to be achieved is acceptable risk levels. 

Good management practice requires that safety professionals who are to make or arrange for risk-based system audits obtain acceptance from personnel to whom counsel is given of a definition of an audit and what an audit is to accomplish. Several writers have published such definitions and outlined what information the audit should provide. Their views are helpful. 

SwS is a special aspect, and subset, of system safety it is also sometimes referred to as SwSS. The scope and coverage of SwS includes computer software, firmware, and programmable logic arrays. SwS is primarily concerned with application software developed as part of a system development program. However, due to the permeating nature of software, SwS must also consider operating systems, compilers, software tools, and reused software, including any form of COTS software that is utilized in the system. In the case of SwS, actual hazard risk cannot be calculated thus, acceptable risk is nebulous and is based on a diverse SwS process. 

So, although the goal-based approach provides a designer with acceptable levels of safety which need to be accomplished in the design (as in Chapter 8), the user of the system will need to conduct further assessments (as in Chapter 9) to consider how the system is put into operational use and what risks said use will hold. 

Toxicologists tend to focus their attention primarily on c.xtrapolations from cancer bioassays. However, tlicrc is also a need to evaluate the risks of lower doses to see how they affect the various organs and systems in the body. Many scientific papers focused on tlic use of a safety factor or uncertainty factor approach, since all adverse effects other than cancer and mutation-based dcvclopmcnUil effects are believed to have a tlu cshold i.e., a dose below which no adverse effect should occur. Several researchers have discussed various approaches to setting acceptable daily intakes or exposure limits for developmental and reproductive toxicants. It is Uiought Uiat an acceptable limit of exposure could be determined using cancer models, but today tliey arc considered inappropriate because of tlircsholds. ... 

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