Risk assessment likelihood

In the first chapter we wiU introduce the concept of functional safety and the need to express targets hy means of safety integrity levels. Functional safety will be placed in context, along with risk assessment, likelihood of fatality, and the cost of conformance. 

Hazard analysis (HAZAN) is a quantitative way of assessing the likelihood of failure. Other names associated with this technique are risk analysis, quantitative risk assessment (QRA), and probability risk assessment (PRA). Keltz [44] expressed the view that HAZAN is a selective technique while HAZOP can be readily applied to new design and major modification. Some limitations of HAZOP are its inability to detect every weakness in design such as in plant layout, or miss hazards due to leaks on lines that pass through or close to a unit but cany material that is not used on that unit. In any case, hazards should... 

Risk is often defined as the likelihood of a certain event times a measure of the severity of its consequences. Most risk assessment studies concentrate on estimating the likelihood of certain events. They often concern the release of chemicals, or accidents in engineering projects and the project outcome. In thi.s section, the subject of accidents is not covered. Risk assessment (RA), as a technique, has been adopted by various national governments, by EU, and by OECD.-... 

Risk Assessment A methodology for identifying the sources of risk in a system and for making predictions of the likelihood of systems failures. 

Risk Assessment - to identify the risk of an EHS accident associated with a particular EHS operation and, if required, determine the likelihood and consequences of the accidental release in order to develop a risk reduction plan that focuses on accident prevention... 

There are many definitions of the word risk. It is a combination of uncertainty and damage a ratio of Itazards to safeguards a triplet combination of event, probability, and consequences or even a measure of economic loss or human injury in terms of both the incident likelihood and tlie magnitude of the loss or injuiy (AICliE, 1989). People face all kinds of risks eveiyday, some voluntarily and otliers involuntarily. Tlierefore, risk plays a very important role in today s world. Studies on cancer caused a turning point in tlie world of risk because it opened tlie eyes of risk scientists and healtli professionals to tlie world of risk assessments. 

Since 1970 tlie field of healtli risk assessment Itas received widespread attention witliin both tlie scientific and regulatoiy committees. It has also attracted tlie attention of the public. Properly conducted risk assessments have received fairly broad acceptance, in part because they put into perspective the terms to. ic, Itazard, and risk. Toxicity is an inlierent property of all substances. It states tliat all chemical and physical agents can produce adverse healtli effects at some dose or under specific exposure conditions. In contrast, exposure to a chemical tliat lias tlie capacity to produce a particular type of adverse effect, represents a health hazard. Risk, however, is tlie probability or likelihood tliat an adverse outcome will occur in a person or a group tliat is exposed to a particular concentration or dose of the hazardous agent. Tlierefore, risk can be generally a function of exposure and dose. Consequently, healtli risk assessment is defined as tlie process or procedure used to estimate tlie likelihood that... 

The term risk assessment is not only used to describe the likelihood of an ad crse response to a chemical or physical agent, but it has also been used to describe the likelihood of any unwanted event. This subject is treated in more detail in tlie next Part. These include risks such as explosions or injuries in tlie workplace natural catastrophes injury or deatli due to various voluntary activities such as skiing, sky diving, flying, and bimgee Jumping diseases deatli due to natural causes and many others. ... 

A risk estimate indicates Uie likelihood of occurrence of the different types of health or enviroinnental effects in exposed populations. Risk assessment should include both liuimn health and environmental evaluations (i.c., impacts on ecosystems). Ecological impacts include actual or potential effects on plants and animals (other than domesticated species). The number produced from the risk characleriznlion, representing the probability of adi crse... 

Human health risk assessment estimates the likelihood of health problems occurring if no cleanup action were ttikcn at the site. To cstiimite the baseline risk at a site, the following four-step process should be taken to detennine Uie possible human risk which will then detennine what sort of corrective action should be employed ... 

Health risk assessment is defined as Uie process or procedure used to estimate Uie likelihood that humans or ecological systems will be adversely affected by a chemical or physical agent under a specific set of conditions. 

Risk iuialysis of accidents serves a dual purpose. It estimates tlie probability tliat iui accident will occur and also assesses the severity of the consequences of an accident. Consequences may include dmnage to tlie surrounding enviromnent, financial loss, injury to life and/or deatli. This Part of the book (Part IV) is primarily concerned witli tlie metliods used to identify liazards and causes and consequences of accidents. Issues dealing witli healtli risks have been explored in die previous Part (III). Risk assessment of accidents provides an effective way to help ensure eidier diat a mishap will not occur or reduces the likelihood of an accident. The result of die risk assessment also allows concerned parties to take precautions to prevent an accident before it happens. 

Risk assessment, an obvious precursor to risk management, first identifies a hazard and then qtrantifies the likelihood of occurrence (hazard assessment) and the impact (expostrre assessment) associated with each hazard event. 

In environmental risk assessment, the objective is to establish the likelihood of a chemical (or chemicals) expressing toxicity in the natural environment. Assessment is based on a comparison of ecotoxicity data from laboratory tests with estimated or measured exposure in the field. The question of effects at the level of population that may be the consequence of such toxicity is not addressed. This issue will now be discussed. 

As probabilistic exposure and risk assessment methods are developed and become more frequently used for environmental fate and effects assessment, OPP increasingly needs distributions of environmental fate values rather than single point estimates, and quantitation of error and uncertainty in measurements. Probabilistic models currently being developed by the OPP require distributions of environmental fate and effects parameters either by measurement, extrapolation or a combination of the two. The models predictions will allow regulators to base decisions on the likelihood and magnitude of exposure and effects for a range of conditions which vary both spatially and temporally, rather than in a specific environment under static conditions. This increased need for basic data on environmental fate may increase data collection and drive development of less costly and more precise analytical methods. 

It is advisable, then, in a tiered approach to concentrate first on crops and activities (scenarios) that are considered to be relevant with respect to the expected level of exposure and to exclude those not relevant. Second, whether or not the toxicological properties of the product may lead to general restrictions on re-entry should be investigated. If both the likelihood of reentry and the hazard due to the toxicity of the compound cannot generally be neglected, a risk assessment over several steps should be carried out. The assessment may be based on surrogate data and "worst-case" assumptions at first and then refined, if necessary. One possible approach to a tiered evaluation procedure is presented in Figure 1. 

Table 3 describes the main parts of an environmental risk assessment (ERA) that are based on the two major elements characterisation of exposure and characterisation of effects [27, 51]. ERA uses a combination of exposure and effects data as a basis for assessing the likelihood and severity of adverse effects (risks) and feeds this into the decision-making process for managing risks. The process of assessing risk ranges from the simple calculation of hazard ratios to complex utilisation of probabilistic methods based on models and/or measured data sets. Setting of thresholds such as EQS and quality norms (QN) [27] relies primarily on... 

Risk assessment Risk (R) assessment is the process of determining the likelihood of an adversary (T) successfully exploiting vulnerability (V) and the resulting degree of consequences (C) on an asset. A risk assessment provides the basis for rank-ordering risks and thus establishing priorities for the application of countermeasures. 

Risk Assessment The scientific process of evaluating the toxic properties of a chemical and the conditions of human exposure to it, in order to ascertain the likelihood that exposed humans will be adversely affected, and to characterize the nature of the effects they may experience. It may contain some or all of the following four steps hazard identification, dose-response assessment, exposure assessment, and risk characterization. 

For acute toxicity, corrosivity and skin and eye irritation, values for the NOEL (or NOAEL or LOAEL) are not derived. Therefore, the only option is to determine whether the substance has an inherent capacity to cause such effects and to make a qualitative risk assessment to evaluate the likelihood of an adverse effect occurring in use. 

Risk assessment for any given environmental compartment is a comparison of the PEC with the PNEC, i.e., the PEC PNEC ratio. If this ratio is below 1, there is no immediate concern. If the ratio is above 1, the assessor decides on the basis of its value and other relevant factors what conclusions apply. If it has not been possible to derive a PEC/PNEC ratio, the risk assessment is a qualitative evaluation of the likelihood that an adverse effect will occur. 

Risks have so far been presented in quantitative terms, with a discussion of some of the conditions that would have to be true if the risk were to be considered accurate. Additional commentary on the likelihood that these conditions are correct, and the likely effect on risk (to increase or decrease it) were any not to be, is a critical part of the risk characterization. Step 4 in the risk assessment framework. 

The approach used in an FHA is to assume ignition of releases. In reality, not all releases result in afire. The likelihood of ignition can be addressed in the quantitative risk assessment process. However, in an FHA it is important to identify if ignition sources are present for the fire scenarios to occur. In some instances, fire scenarios can be eliminated from analysis because of the lack of a credible ignition source. 

In some cases, after completing the consequence portion of the analysis, the impact of the consequences is deemed so severe that the company may decide to provide fire protection that will provide mitigation without completing the likelihood analysis. It is important to take the time to analyze the consequences (conduct an FHA) and determine if reasonable mitigation measures can be applied before continuing with the fire risk assessment. Credit for additional mitigation measures can be taken in the fire risk assessment. 

In a first screening step of the exposure assessment, the likelihood of an exposure of the three populations (workers, consumers, and man indirectly via the environment) to the substance under consideration has to be evaluated. If in the screening step it is indicated that exposure to one or more of the human populations does not occur or when the expected exposure is so low that it can be neglected further in the risk characterization phase, no further assessment is needed and the conclusion can be mentioned in the risk assessment report. 

Ecological risk assessment The process that evaluates the likelihood that adverse ecological effects of differing magnitudes may occur or are occurring as a result of exposure to one or more stressors. 

The PAF indicates the likelihood that adverse ecological effects will occur as a result of TBT exposure in a particular area. This value can be interpreted as the probability that a randomly selected exposure concentration will exceed species sensitivity. The probabilistic risk assessment was performed on the clustered data for harbours and for open waters, as well as for each harbour and open water separately. Only water systems for which exposure concentrations were measured at two or more locations were selected (all open waters and 19 out of 30 harbours). 

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