Suggested Risk Matrix

A No further action or safety studies required. Individual personnel judgement required for 

B Document process safety studies, hazard and risk reducing measures. Consider feasibility 

C Document process safety studies, evaluate feasibility of additional risk reducing features and 

E Additional process safety studies and risk reducing measures are mandatory to achieve lower 

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Many standards, including lEC 61S08, suggest the familiar risk matrix approach, such as in Table 1, for deciding whether risks are tolerable or not. The Roman numerals I to IV represent risk classes, where risk class I is intolerable and IV is acceptable. Although lEC 61508 is clear that this is an example only, we have observed many projects which have attempted to apply this matrix directly without question. 

The use of risk matrix has been depicted in Fig. 1/3.3.3-1 through a simple example of single risk target pertinent to one cement plant. In this example, it is seen that for the same cause there could be two different risk levels as shown by differences in hatch lines. In the example, the same likelihood has been considered for both the cases. Since the risk level is medium, it is accepted with suggestion of installing additional devices to reduce the risk level. 

Tiering is often applied in risk assessment in order to reduce expenditures in time, money, and labor when the assessment requires only simple and possibly conservative output. Table 5.3 provides a suggested tiered approach in mixture extrapolation and is further described in the bulleted list below. The tiering is based on the way that mixture mechanisms are addressed in the approach. It is assumed that issues such as matrix and media extrapolation have been addressed according to the methods described in the pertinent chapters. 

Long-term animal studies of dermal exposure to crude oil can be used to set a no observed adverse effect level (NOAEL) that can be used to predict safe human exposure levels for both dermal and systemic effects. A reference dose of 0.04 mg kg day has been suggested for exposures to crude oil. The individual aliphatic and aromatic fractions of crude oil have also been evaluated for toxicity and sufficient information exists to set references doses for these fractions. An understanding of the exposure to the individual fractions is necessary to use this process. The use of the reference dose for either crude oil as a whole or the individual fractions is preferable to evaluating only the toxic constituents in crude oil. This latter strategy is commonly employed in risk assessment however it ignores the hydrocarbon matrix within which these toxic chemicals are found. This hydrocarbon matrix affects the exposure to... 

Markers of systemic inflammation (e.g., C-reactive protein [CRP] and interleukin-6 [IL-6]) have been proposed to be nontradi-tional risk factors for cardiovascular disease in patients with type 2 diabetes mellitus. Matrix metalloproteinase-9 (MMP-9) has been implicated in the pathogenesis of atherosclerotic plaque rupture, which raises the possibility of the use of MMP-9 levels as a marker for future MI or UA. In vitro and animal studies suggest that thiazolidinediones can reduce the expression of these markers. Rosiglitazone reduces serum levels of MMP-9 and the proinflammatory marker CRP in patients with type 2 diabetes, which indicates potentially beneficial effects on overall cardiovascular risk. The management of UA and NSTEMI is covered in detail in Chap. 16. 

The major rationale for the cleanup of sites contaminated with TCDD is that the contamination by this highly toxic compound presents a major risk to human health. Risk is made up of the inherent hazard of the compound and the extent of exposure to the compound. Operationally, it has been assumed that most of the TCDD that can be detected by chemical analysis is available to cause toxicity. There has been little evidence until recently regarding the validity of this assumption. Several studies (discussed below) have suggested that the entire amount of TCDD that can be detected in a soil sample may not be completely bioavailable. Rather, some portion of the TCDD may be too tightly sorbed to the matrix to be released in biological systems. Further, the presence of other chemicals in the matrix may interfere with gastric uptake of TCDD or with the receptor mediated toxicity of TCDD. 

The risk for a land-based geologic repository is that a combination of more or less unpredictable circumstances could lead to rupture of the protective barriers around the waste matrix, followed by dissolution and transport of the most hazardous products by water to a place where it can enter into the food chain. Therefore a clay layer (e.g. bentonite) between the canister and the rock wall is suggested, partly to act as a mechanical buffer, so that even considerable slippage caused by earthquakes would have little effect on the mechanical integrity of the canister and partly to reduce water flow around the canister. 

Table 14.6 is a Hazard/Risk Assessment Matrix that also includes suggested action levels. It is an adaptation of one of two examples... 

Hayes and Khosla (1992) suggested that PA may be neutral in normocholesterolaemic subjects if the diet contains little cholesterol and linoleic acid intake is adequate. Fattore and Fanelli (2013) reviewed the scientific literature on the evidence of the relationship between palm oil and adverse effeets on hmnan health and concluded that there is no elear evidence of a negative role of PA on health and much less of native palm oil, whieh is a eomplex alimentary matrix, in whieh PA is only one of its components. However, more reeent lipid research on the topie seems to have reconsidered the negative role of dietary SFAs as a risk factor for cardiovascular diseases. For instance, lamic acid and myristic acid have a greater total cholesterol-raising effect than PA, whereas stearic acid has a neutral effeet on the concentration of total serum eholesterol, including no apparent impact on either LDL or HDL (Daley etal, 2010). 

A quantitative risk assessment attempts to quantify the risk level in terms of the likelihood of an incident and its subsequent severity. Clearly the higher the likelihood and severity, the higher the risk will be. The likelihood depends on such factors as the control measures in place, the frequency of exposure to the hazard and the category of person exposed to the hazard. The severity will depend on the magnitude of the hazard (e.g. voltage, toxicity etc.). HSE suggest in HSG(65) a simple 3x3 matrix to determine risk levels. 

The World Health Organization (2004) has suggested, as an example, a simple risk scoring matrix, as shown in Figure 6.1 ... 

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