Relative risks

Type of pollutant Weight % of volatile organic compounds contained In exhaust gas Relative risk factor... 

Each of the endoscopic imaging procedures is relatively risk free and painless when performed by competent and weU-trained individuals using a local anesthetic. Eetoscopy has the highest risk. There is a 10% increased probabiUty of premature deUvery and 10% higher fetal loss rate. 

Absolute and relative risks Major risk contributors Comparisons with other risks... 

Relative risk results show only the difference between the levels of safety of one or more cases of interest and a reference, or baseline, case. Relative risk estimates can be used (as can absolute estimates) to determine the most efficient way to improve safety at a facility. But, the use of relative risk estimates alone does little to help ensure that the most efficient way is safe enough unless one of the cases meets qualitative safety criteria (e.g., compliance with relevant codes, standards, and/or regulations consistency with current industry practice). 

The advantage of using relative risk results is that you can decide on the best way to improve safety at a facility without having to defend the absolute accuracy of the results. Relative results are also much less likely to be misinterpreted by people unfamiliar with QRA. The disadvantage of using relative results is that they, by definition, cannot give direct advice... 

TABLE 7. Converting Absolute Risk Estimates to Relative Risk Estimates... 

System Absolute Risk Estimate Relative Risk Estimate... 

Whenever possible, relative comparisons of risk should be made (Step 8). Comparing relative risk estimates for alternative strategies avoids many of the problems associated with interpreting and defending absolute estimates. Table 9 contains examples of typical conclusions you can reach using relative risk estimates. In some cases, however, absolute estimates may be required to satisfy your needs. Table 10 contains a list of examples of typical conclusions possible using absolute risk estimates. 

The work required to evaluate risk results will be a function of the objectives of the study. For relative risk studies, this evaluation is usually not very time-consuming. For absolute risk studies, in which many uncertainty and sensitivity cases may have been produced, the risk evaluation step may account for to 35% of the total effort of a large-scale QRA. Chapter 4 discusses the problems associated with interpreting risk results. 

Examples of Possible Conclusions Using Relative Risk Estimates 23 Examples of Possible Conclusions Using Absolute Risk Estimates 24... 

A number of vendors offer software based hazard assessment tools that help determine the magnitude of the hazards involved. With this software, calculations can be made to reflect the hazard for various failures. Some risk ranking software combines hazard assessment with probabilities of occurrence so that the relative risk levels can be assessed. 

MarshaU, J., A. Mundt, M. Hult, T. C. McKealvy, P. Myers, and J. Sawyer (1995). The Relative Risk of Pressurized and Refrigerated Storage for Six Chemicals." Process Safety Progress 14, 3 (July), 200-211. 

The primary motivation of PSAs is to assess the risk of the plant to the public. The immediate purpose of the RSS was to support the Price-Anderson hearings on liability insurance (i.e., assess the financial exposure of a nuclear power reactor operator) a purpose which, even today, is beyond PSA technology. However, PSA is sufficiently precise to provide relative risk comparisons of reactor designs and sites. These uses of PSA were presented at the Indian Point hearings, and in defense of Shoreham. The PSAs for the high-population-zone plants (Limerick, Zion, and Indian Point) were prepared to show that specific features of these plants compensate for the higher population density relative to plants studied in the RSS. 

QRA is generally resource intensive. FEIR, is much less although it uses the framework of QRA for screening and ranking systems by relative risk using order-of-magnitude estimates of the frequencies and consequences of events. It incorporates plant experience and industry data to estimate the potential for future losses. 

Train all personnel in the functioning and value of blowdown during an emergency. This may be achieved by safety specialists explaining the various hazards and relative risks of blowing down and failing to depressurize. 

Guidelines for Chemical Process Quantitative Risk Analysis (CPQRA Guidelines) builds on the earlier work to show the engineer how to make quantitative estimates of the risk of the hazards identified. The quantitative estimates can identify the major contributors to risk. They can also help to define the most effective ways to a safer process by indicating relative risk reduction from proposed alternate process safeguards and measures. 

In the case-control design, a group with a disease (cases) is compared with a selected group of nondiscased (control) individuals with respect to exposure. The relative risk in control studies can only be estimated as the incidence rate among exposed individuals and cannot be calculated. The estimator used is the odds ratio, which is the ratio of the odds of exposure among the cases to that among the controls. 

Category Systolic [mm Hg] I Diastolic [mm Hg] Stroke mortality relative risk... 

Ibuprofen is the most thoroughly researched 2-ary lpropionic acid. It is a relatively weak, non-selective inhibitor of COX. In epidemiological studies, ibuprofen compared to all other conventional NSAIDs, has the lowest relative risk of causing severe gastrointestinal side effects. Because of this, ibuprofen is the most frequently used OTC ( over the counter , sale available without prescription) analgesic. Ibuprofen is highly bound to plasma proteins and has a relatively short elimination half-life ( 2 h). It is mainly glucuronidated to inactive metabolites that are eliminated via the kidney. 

Odds Ratio (OR)—A means of measuring the association between an exposure (such as toxic substances and a disease or condition) which represents the best estimate of relative risk (risk as a ratio of the incidence among subjects exposed to a particular risk factor divided by the incidence among subjects who were not exposed to the risk factor). An odds ratio of greater than 1 is considered to indicate greater risk of disease in the exposed group compared to the unexposed. 

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