Logical process risk assessment

Fault tree analysis is based on a graphical, logical description of the failure mechanisms of a system. Before construction of a fault tree can begin, a specific definition of the top event is required for example the release of propylene from a refrigeration system. A detailed understanding of the operation of the system, its component parts, and the role of operators and possible human errors is required. Refer to Guidelines for Hazard Evaluation (CCPS, 1992) and Guidelines for Chemical Process Quantitative Risk Assessment (CCPS, 2000). 

Description of process/environment Quality-related critical parameters Purpose and objectives of the system Major benefits of the system Special requirements Specific training needs System operating strategy Related GMP compliance/regulations Physical and logical boundaries System GMP risk assessment System validation rationale Life-cycle documentation Assumptions and prerequisites Limitations and exclusions Quality-related critical parameters/data Standard operating procedures System requirement specification Supplier and system history... 

The immediate future in risk assessment will focus on the difficult but necessary task of integrating experimental data from all levels into the risk assessment process. A continuing challenge to toxicologists engaged in hazard or risk assessment is that of risk from chemical mixtures. Neither human beings nor ecosystems are exposed to chemicals one at a time, yet logic dictates that the initial assessment of toxicity start with individual chemicals. The resolution of this problem will require considerable work at all levels, in vivo and in vitro, into the implications of chemical interactions for the expression to toxicity, particularly chronic toxicity. 

Ecological risk assessments evaluate ecological effects caused by human activities such as draining of wetlands or release of chemicals. The term "stressor" is used here to describe any chemical, physical, or biological entity that can induce adverse effects on individuals, populations, communities, or ecosystems. Thus, the ecological risk assessment process must be flexible while providing a logical and scientific structure to accommodate a broad array of stressors. 

While risk assessment in the context of protecting public health has been performed for many years, it is the 1983 U.S. National Academy of Sciences Report (Committee on the Institutional Means for Assessment of Risks to Public Health Commission on Life Sciences National Research Council 1983) that has served as the tenet for practicing risk assessors (see Chapter 1). Risk assessment was defined as the characterization of the potential adverse health effects of human exposures to environmental hazards. The predictive aspect of risk assessment was set by the use of the word potential. A fundamental expectation of the risk assessment process was that it should attempt to accm-ately predict adverse effects before there is evidence of disease in the population. Thus, risk assessment goes beyond the mere description of epidemiological and clinical case-control studies. In that report, the committee defined logical components of a risk assessment which still serve as guiding principles today. They were and are (a) hazard assessment or the qualitative determination that a stressor poses a hazard as evidence by causal evidence of an ill effect,... 

When the products formed by metabolic processes are toxico-logically insignificant and, when this is a known fact, the findings may be valuable in assessing pesticide risk. Contrarily, a number of pesticides yield metabolites known to be highly toxic and these materials may be taken into account in the risk assessment process. Too many times, however, the isolation and identification of pesticide metabolites tell us very little about risks that may be associated with the use of a particular chemical because the information can not be related to in vivo toxicological significance. 

This International Standard addresses the application of safety instrumented systems for the Process Industries. It also deals with the interface between safety instrumented systems and other safety systems in requiring that a process hazard and risk assessment be carried out. The safety instrumented system includes sensors, logic solvers and final elements. 

Procedures set forth establish that, in the risk assessment process, both the expected severity of consequences of an incident resulting from a hazard s potential being reahzed and the probabihty of its occurrence be evaluated. In a logical sequence, the guidehne indicates that after the hazard analysis and risk assessment are concluded, decisions are to be made about whether the risk is acceptable or whether further mitigation is necessary. 

Risk assessments need to be canried out by experienced and competent people who are knowledgeable about the hazards of the substances, the equipment and the operations being reviewed. It is a subjective process which cannot normally be validated mathematically, and is essentially practical. Those involved in the assessment need to think logically and laterally, look beyond the obvious and have good interactive skills to tease out crucial information. 

Risk assessments for a small unit or department can be carried out by one person but for larger and more complex areas it may be appropriate to involve a small team of people, e.g. safety adviser, area engineer, production team leader, and an operator. To ensure that all facets that could be affected by the hazards are considered a risk assessment should follow a series of logical steps based on a thought-out strategy. A generic risk assessment process will ... 

Wholeness of the logical fact net, that is the safety case, is being assured by adherence to the Change Safety Analysis, Risk Assessment and Management process for its development. In ad tion, the fact net must be transparent tlnoughout its own life cycle, involving all the necessary competences in its development and review. 

After the hazard assessment has been conducted and the data has been collected, it should be organized in a logical outline that will estimate the potential for employee injury The organized data will help to decide the type of hazard(s) involved, the level of risk, and the seriousness of potential injury The appropriate levels of PPE are then selected based on the hazard determination and the availability of PPE. The user should be properly fitted for the specified PPE, and the employer should make sure that it is comfortable to wear. Hazard reassessments should be conducted as necessary based on the introduction of new or revised processes, equipment, and accident experience, to ensure the continued suitability of selection of the proper PPE. 

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