Risk estimation 275-7 matrix

In establishing the risk estimation matrix according to Table 22.4, the following two anchorage points defining the acceptance limits have been applied ... 

Steps 4 and 5 are not straightforward activities, especially when it comes to long-term effects, i.e. the development of occupational diseases. For accidental exposures to acute toxic/corrosive chemicals, the risk-estimation matrix of Table 22.5 can be used. A similar matrix for use with other chemical exposure assessments is shown in Table 23.2. The application of it involves a number of crucial decisions concerning ... 

Even if a correlation is below the conventional level of significance, consideration should be given to whether it might alter the risk estimate, and it may be prudent to include it. When measnred or estimated correlations are nsed to specify dependencies in Monte Carlo models, it is important to check that the matrix of correlations satisfies mathematical constraints (Table 2.3). 

Using the consequence and likelihood categories, risk matrix, and risk evaluation criteria, the team reviewed three release scenarios (small, medium, and large) for the segments identified for each of the chemical movements. The result of the semi-quantitative risk estimation for this facility s hazardous material transportation operation is detailed in Table 4.12. From this results table, the following are determined ... 

Accurate assessment of human health risks associated with oral exposure to metals requires knowledge of the fraction of the dose absorbed into the blood. This information is important for As-contaminated environmental media, such as soil and mine waste, because metal contaminants exist in a variety of soluble and insoluble forms and may be contained within particles of inert matrix, such as rock or slag. Physicochemical properties such as these influence the enteric absorption fraction (bioavailability) of ingested metals. Therefore, site-speciflc data on metal bioavailability in the environmental media of concern will increase the accuracy and decrease the uncertainty in human health risk estimates. 

As far as methods for risk assessment at workplace are concerned. Risk Assessment Matrix method is the most popnlar one. Risk estimation entails evaluating both the severity and frequency of hazardous events. 

Risk estimation refers to putting the frequency and consequence components together, either through a formula such as Risk = frequency X consequence, or by placing the hazardous event on a scatter graph or matrix of frequency versus consequence. 

A risk assessment matrix is used to estimate the potential consequences of an adverse outcome based on a combination of what is perceived as the potential severity and the probability of exposure to the hazard being evaluated. 

The Standard provides guidance and examples of methods of undertaking risk estimation. These methods include risk matrix, risk graph, numerical scoring, and hybrid approaches. Figure 9.3 shows the general elements of risk associated with a particular hazardous situation. 

THE RISK ESTIMATION USING THE MATRIX TYPE RISK MODEL... 

Figure 11. (below) Proposal for a Farmer Matrix for comparing accumulated risk estimates. 

The Risk Assessment Matrix (RAM) is coimnonly used to map the various risks associated with a system under stu. As indicated in Fig. 2 the matrix shows a scale for increasing likehhood of a particular event and the other scale shows the severity of the consequence for that particular event. The yellow area of the matrix, as low as reasonably practical (ALARP) to indicate the level used as the limit for which risks should be mitigated. Each company should define the ALARP region in their RAM. Qualitative values from A to E are assigned for likehhood (equivalent numerical values from 0 to 5 are also used to estimate a risk index value). For Tambaredjo, the risks indices numbered in Table 2 are shown in Fig. 2. Risks 1 to 3 require further considerations. 

Table 22A Matrix for risk estimation for a workplace with about 100 employees...

Table 23.2 Matrix for risk estimation for exposure to chemical agents...

To comply with item 6, operators have to identify the major hazards they face, estimate the frequency and consequences of each risk, combine the frequency and the consequences in some kind of risk-ranking matrix, and finally set some criteria for determining which are the high-priority risks. Some operators chose to identify the risks by the outcomes, such as a derailment or a collision, while other operators chose to identify the root cause of the risk, such as brake failures, defective vehicles or track-circuit failures. 

A risk assessment matrix is placed on the risk card to allow evaluation of the estimates of what is the perceived potential event severity and the frequency of exposure to a hazard. A brief list of guidelines and questions are placed on the card to guide the assessment and discussions. 

Data from chemical characterization were used to estimate possible adverse effects on humans and the environmental receptors. Following previously published works [11, 19], a hypothetic scenario was set up to assess the risk posed by these non-conventional matrix an accidental leachate release into ground-water resulting in 1 100 and 1 1,000 dilutions of the leachate compounds, which have been subjected to dilution as the leachate mixes with the groundwater (Fig. 3). 

In the United States as well as in Europe, the use of matrix extrapolation techniques for estimating the bioavailability of toxicants is officially encouraged. An example is the Ohio EPA (1996) recommendation to use hardness-corrected water quality criteria for heavy metals. The EUSES (Jager 2003) computer program of the European Union for predicting the risk of new compounds to be released into the environment corrects for partitioning processes in the calculation for all types of effects. 

Answers to these questions provide preliminary insight into the variables for which extrapolation can be considered most urgent, due to an estimated numerical influence on the assessment results. For example, matrix and media extrapolation might be identified as the most important modifying factor, and the risk assessment might fully focus on this factor in the lowest tier. Information on issues for which no extrapolation will be applied need to be kept in the dossier, for reporting which factors have been considered and what numerical influence (magnitude and direction) is expected. 

Ranking The qualitative estimation of risk from severity and likelihood levels, in order to provide a prioritizing of risk based it s magnitude (refer to corporate risk matrix for ranking based on severity and likelihood levels). 

Sequential extraction procedures include successive sample treatment with a series of extractants selected on the basis of their ability to dissolve analytes bound to different components of the matrix. The use of sequential extraction procedures simulating natural phenomena, (e.g., acid rain), can deliver detailed information about the origin, mode of occurrence, physiological availability, and mobilization of trace elements. It is also possible to estimate toxicological risk ensuing from the presence of different forms of metals and various phases containing those metals. A... 

The solubility of organic compounds in selected solvents may be estimated from the like dissolves like rule of thumb. Whilst this approach is adequate, it is at best only qualitative and does not take into account the matrix and other effects present. Cocktails of solvents of different polarity can be prepared to give the same polarity as solvents which have or may be withdrawn from use for health and safety reasons. However, the presence of water in the sample can affect the polarity of the solvent and ultimately the extract. Soils can be oven dried up to 35°C with the significant risk of loss of volatiles or chemically dried (for instance, using magnesium sulfate monohydrate) to avoid volatile loss (see Chapter 8). 

Development and Use of Matrix Population Models for Estimation of Toxicant Effects in Ecological Risk Assessment... 

In this chapter, an overview of the development and use of matrix population models for estimation of toxicant effects is presented. Matrix models are one of the modeling approaches that can be used to determine whether populations of organisms will remain the same, increase, or decline, and thus have great potential for use in ecological risk assessment. 

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