Components of a risk assessment

Many aspects of risk assessment are still of a qualitative nature, however, within the EU many models and procedures are now available or under development to allow a more quantitative risk assessment to be conducted. However, it has to be noted that even these quantitative risk assessments are typically conservative in nature and represent a realistic worst-case scenario through the lifecycle of a biocidal product, i.e. production, use and disposal. 

Under the BPD, no authorisation of a biocidal product will be granted unless a risk assessment is submitted and accepted by the Member State competent authority. Risk assessments are usually separated into three main sections as outlined in the introduction  

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Calculate the transport component of a risk assessment model... 

Perhaps the easiest definition of ecological risk assessment is the probability of an effect occurring to an ecological system. Note that the word "probability" is key here. Important components of a risk assessment are the estimations of hazard and exposure due to a stressor. 

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,... 

Thus, the distinction between the hazard (an inherent toxic property of a chemical that may or may not be manifested, depending on exposure potential) and risk (the consequences of being exposed to a hazardous chemical at a particular exposure level) is critical (Purchase, 2000). Each component of a risk assessment—hazard identification, dose-response evaluation, and exposure assessment—is essential for evaluating the potential risks associated with the use of a substance such as a nanomaterial. The components of a risk assessment are universal in their application for assessing the hazards and risks of chemicals or products for a variety of industries or environmental exposures, regardless of the types of chemicals of interest (such as solvents, fibers, particulates and nanomaterials). 

The chemical concentrations identified in the data evaluation component are combined with all of these exposure or intake assumptions into equations to estimate a dose in units of milligrams chemical per kilogram body weight per day. These are the same units in which toxicity data are reported, as discussed in chapter 7. For the gas station example, the results of this step would include chemical-specific dose estimates for all complete exposure pathways for each receptor. These dose estimates are combined with the toxicity values discussed below in the risk characterization component of a risk assessment. 

This is the component of a risk assessment where risks are estimated by combining exposure and toxicity information for the chemicals at a site. There is an important distinction between cancer and non-cancer chemicals in this step. These two types of effects are separately discussed below. 

The determination of the estimated levels of exposure is obviously a critical component of the risk assessment process. Both pesticide residue levels and food consumption estimates must be considered. Methods for determining exposure are frequently classified as deterministic and probabilistic methods (Winter, 2003). 

It is important that both the qualitative and quantitative characterization be clearly communicated to the risk manager. The qualitative characterization includes the quality of the database, along with strengths and weaknesses, for both health and exposure evaluations the relevance of the database to humans the assumptions and judgements that were made in the evaluation and the level of confidence in the overall characterization. The quantitative characterization also includes information on the range of effective exposure levels, dose-response estimates (including the uncertainty factors applied), and the population exposure estimates. Kimmel et al. (2006) reviewed many of the components of the risk characterization for reproductive and developmental effects and provided a comprehensive list of issues to be considered for each of the components of the risk assessment. 

As a first step in the risk assessment of chemicals, it is essential to have an insight into the magnitude and duration of exposure. Following the toxicological principle that dose determines the effect, one may assume that no exposure means no risk. In the case of chemical mixtures, a proper assessment of exposure assists in adequately interpreting the interacting effects of chemicals. So, exposure assessment is an essential component of any risk assessment study of mixtures, since it can be used to reduce uncertainty and provide data. 

Being able to predict the human health risk from exposure to airborne chemicals can be complex, requiring reliable analysis of human exposure. While the basic principles of risk assessment are applicable to various conditions of exposure, characterizing how an individual s health status can significantly influence the threshold for effects can be a most challenging component of the risk assessment process. One needs to consider the overall scientific weight-of-evidence to predict whether or not an individual may be uniquely susceptible to certain... 

A particularly important component of the risk assessment concerns the assumptions and data used to develop an estimate of human exposure - the human dose. Elements of the dosimetry problem were described in Chapter 2 and we do not intend to go into them in more detail here. Certain additional aspects of this issue should be brought out, however, because they critically affect the meaning that is to be attached to the risk estimates produced under the regulatory principles. 

A risk assessment will be conducted as part of inspection and activity planning in order to rninirnise health and safety risks. This assessment shall include, inter alia, an evaluation of environmental, structural, physical and chemical hazards as weU as radiation, endemic diseases and appropriate ways of managing them. Where this evaluation implies undue knowledge of issues protected by confidentiality restrictions, the relevant components of the risk assessment in terms of level and measures to be adopted shall be provided by the inspected State Party. Risk assessments will be updated during inspections as appropriate. Risk assessment procedures wdl be standardised throughout the OPCW. 

The risk assessment is a primary component of the risk management process. The objective of a risk assessment is to identify risks to organizational assets and propose an achievable level of protection that is commensurate with the level of risk, without exceeding that level of risk so that it will be cost effective. Risk is a function of the values of threat, vulnerability, and collateral damage via loss occurrence. The objective of risk management is to create a level of protection that mitigates vulnerabilities to threats and their potential consequences, thereby reducing risk to an acceptable level. Ideally, all risk would be eliminated. However, in practicality the elimination of risk is not feasible (Department of Homeland Security, 2008). 

Figure 2.71 shows an example SCF thread for the brake function in an automobile system. It was determined from FHA of this hypothetical system that the brake function was safety-critical, because if the braking function failed when needed it could lead to a loss of life mishap. All of the systems (or subsystems) in the brake function are identified in this thread and they in turn become safety-critical. Further HA can now be performed on these critical components and a risk assessment performed. Derived design safety requirements can be generated for each element as necessary to mitigate unacceptable risk. This thread can be used to understand the HCFs and their interrelationships within the thread. 

Start by doing a risk assessment and identify those things on which continuity of business depends power, water, labor, materials, components, services, etc. Determine what could cause a termination of supply and estimate the probability of occurrence. For those with a relatively high probability (1 in 100) find ways to reduce the probability. For those with lower probability (1 in 10000) determine the action needed to minimize the effect. The FMEA technique works for this as well as for products and processes. 

In essence, the earlier components of this overall assessment process are mainly deterministic in character (albeit with some probabilistic elements), whereas the later stages are mainly probabilistic. Not all elements of the process are quantifiable (with any degree of confidence), however and the socicii-political-cultural context of any downstream decision-making process may be intensely uncertain. Such uncertainties make the process of risk communication and debate a complex and sometimes unpredictable undertaking. It is essential therefore that those elements of the risk management process that cein be objectively einalysed and evaluated (either qualitatively or quantitatively, as appropriate) are so assessed. 

A CSR is a risk assessment, following the general provisions of Annex I of the proposed REACH Regulation, with extra guidance in Annex IB for substances that are components of preparations. These general principles correspond with the current EU practice for notified new substances and priority existing substances, as described more fully in Section 14. The ECA will develop software to help registrants prepare the CSR. It is essential to have input from downstream users to prepare the risk assessment for the CSR, which... 

The science policy components of risk assessment have led to what have come to be called default assumptions. A default is a specific, automatically applied choice, from among several that are available (in this case it might be, for example, a model for extrapolating animal dose-response data to humans), when such a choice is needed to complete some undertaking (e.g., a risk assessment). We turn in the next chapter to the conduct of risk assessment and the ways in which default assumptions are used under current regulatory guidelines. We might say we have arrived at the central subject of this book. 

When epidemiological studies form the basis for the risk assessment of a single chemical or even complex mixtures, such as various combustion emissions, it may be stated that in those cases the effects of combined action of chemicals have been incorporated. Examples can, for instance, be found in the updated WHO Air Quality guidelines (WHO 2000). Thus, the guideline value for, e.g., ozone was derived from epidemiological studies of persons exposed to ozone as part of the total mixture of chemicals in polluted ambient air. In addition, the risk estimate for exposure to polycyclic aromatic hydrocarbons was derived from studies on coke-oven workers heavily exposed to benzo[fl]pyrene as a component of a mixture of PAH and possibly many other chemicals at the workplace. Therefore, in some instances the derivation of a tolerable intake for a single compound can be based on studies where the compound was part of a complex chemical mixture. 

To help address these issues, we define a new component for use in conceptual models the units of analysis. These are the lowest levels of biological, spatial, and temporal scale used in the quantitative part of the risk assessment (e.g., individual iterations in a simulation model). They also define the biological, spatial, and temporal units of the measures that will be needed as inputs to the assessment model. 

The risk, competitiveness conservation data summary module organizes data from the risk, competitiveness, and conservation components of a CTSA together with data from the process safety assessment, market information, and international information modules to 1) identify the tradeoff issues associated with any one substitute and 2) compare the tradeoff issues across substitutes. 

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