Risks acceptable

Fewtrell and Bartram (2(X)1) provide some parameters for acceptable risk determination. They include the following  

All of these parameters pose problems. For example, if the cost of reducing the risk is greater than the costs saved, then, rather than declaring this to be the acceptable level of risk, it may be more responsible simply not to carry out that particular activity. Similarly, saying that the money could be better spent elsewhere may simply indicate that a bigger budget is needed, not that a level of acceptable risk has been defined. 

Formal Safety Assessments (FSAs) are built around the concept of acceptable risk. For example, the decision as to whether a firewall should be installed between two sections of the platform will depend on the associated risk, i.e., the nature of the hazard (spreading fire, the consequence of the fire, and the 

Many companies use a value of 0.001—1 fatality every 1000 years. This is known as the IRPA, or Individual Risk per Annum. A more complex term is PLL, or Potential Loss of Life. It combines IRPA with the number of people present to come up with a forecast as to how often a fatality would occur at that facility. 

For example, the designers of an offshore platform have to decide on the length of time that the temporary refuge will survive in the event of an explosion followed by a continuous fire. If the design team settles on a time period of say 30 minutes, then they have implicitly made a decision as to the level of acceptable risk. 

A majority of safety professionals accept the premise that absolute safety, a zero risk state, is not attainable. But, some safety practitioners profess that only a risk-free environment is acceptable. Consider these two examples. 

At a recent safety corrference, a speaker reviewed the hazard analysis and risk assessment methods used in his company and said the outcome to be achieved through the use of those methods was acceptable risk. During the question period, some questioners implied by the nature and tone of their questions that no risk is acceptable. They asked What do you mean by acceptable risk Are you suggesting that some risk is acceptable Acceptable to whom  

The speaker gave a general response saying that a risk is acceptable if the probability of an incident occurring and the severity of harm that might result are low. Thus, the speaker defined the acceptable risk level for his company. 

Safety practitioners attending a course on hazard analysis and risk reduction were outspoken in their opposition to the idea that any level of risk is acceptable. They stated their sineere belief that, in the workplace, attaining zero risk is a legitimate goal. The instmctor could not convince them otherwise. 

Individually and collectively we are risk acceptors. And risk acceptance is situational Variations in the risk levels that individuals and organizations accept in given situations are exceptionally broad. Nevertheless, in an attempt to promote an understanding of the acceptable risk concept, this chapter does the following  

There are many risks people are subjected to in the plant, at home, and elsewhere that can cause harm, health problems, and/or death. Precautions should be taken and enforced based on what is practical, logical, and useful. However, those involved in laws and regulations, as well as the public and, particularly the news media should recognize there is acceptable risk. 

This is the concept that was developed decades ago in connection with toxic substances, food additives, air and water pollution, fire and related environmental concerns, and so on. It can be defined as a level of risk at which a seriously adverse result is highly unlikely to occur but it cannot be proven whether or not there is 100% safety. In these cases, it means living with reasonable assurance of safety and acceptable uncertainty. 

Examples of this concept exists all around us such as the use of automobiles, aircraft, boats, lawnmowers, foods, medical pills and devices, water, air we breathe, news reports, and so on. Practically all elements around us encompass some level of uncertainty and risk. Otherwise as we know it would not exist. 

People are exposed to many risks. Some pose a greater threat than otliers. The following data concerns the probability over a lifetime of premature death per 100,000 people. In USA 290 hit by a car while 

DVR personal statistic (for real) based on personal knowledge of my large family, those that smoke and drank wine died close to 100 years of age. Those that did not smoke or drink died in their 60s (personal genies probably involved). Of course there were/are exceptions. So let tlie smokers continue to smoke and sue someone regardless best not to smoke. Then there are other dilemmas such as exposure to asbestos, etc. that provide for interesting legal cases in USA. [After working with asbestos most of my life (now DVR at age 82) it never bothered me however asthma has been with me since I was born except when 1 was in the Air Force. ] 

Examples of this concept exists all around us such as the use of automobiles, aircraft, 

One limitation is to do with the selection of data to achieve desired goals. The paper to do with the offshore SEMS rule (Transportation Research Board, 2012) discusses this issue. 

With quantitative risk calculation, it was found that discussions on the risk requirements for approving new developments on the Norwegian Continental Shelf quickly became pure numbercrunching exercises. That, in turn, meant it was easy for statisticians to document that the various risks in such projects were within the acceptable limits. 

One company provided the criteria given in Table 1.8 for its design personnel. 

Their instructions were that risk must never be in the intolerable range. High-risk scenarios are tolerable, but every effort must be made to reduce the risk level, i.e., to the broadly tolerable level. 

Looked at in this light, perfect safety can never happen. Nevertheless we should strive toward it because otherwise we accept that people will be injured—which is something that none of us want or accept, and we certainly do not want to quantify (although a goal of zero incidents over a specified time frame may be achievable). 

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W. W. Lawrence, Of Acceptable Risk, Science and the Determination of Safety, William Kaufman Inc., Los Altos, Calif., 1976. 

Numerical Measures of Risk Without risk and the reward for successfully accepting risk, there would be no business activity. In estimating the probabilities of attaining various levels of net present value (NPV) and discounted-cash-flow rate of return (DCFRR), there was a spread in the possible values of (NPV) and (DCFRR). A number of methods have been suggested for assessing risks and rewards to be expected from projects. 

People are more willing to accept risks from which they will receive a direct, tangible benefit. A one-company town will likely have widespread community support for the company and accept the risks of its business—it directly or indirectly provides the livelihood for most families in the community. This may not be the case in an area having a broad-based manufacturing and service economy. Here the relatively small public benefit from a new plant may be outweighed by the public s perception of the plant s risk. People are unwilling to tolerate a given level of risk unless there is a direct benefit to themselves. 

Acceptable risk Accident (sequence) Acute hazard... 

Vrijling, J. K., van Hengel, W. and Houben, R. J. 1998 Acceptable Risk as a Basis for Design. Reliability Engineering and System Safety, 59, 141-150. 

The literature on this subject is so large that it cannot be encompassed in a brief review. N UR CG/CR-1030(1981) is a bibliographical survey of 123 references Covello, 1981 lists 148 rcler-ences. Since no risk should be tolerated if it has no benefits, most of the papers address the question "How safe is safe enough," by comparisons with acceptable risks. (In many cases these "acceptable" risks are really "tolerated" risks in that the cost of reduction does not seem to be warranted.)... 

Starr, 1969 approached this by investigating the "revealed preferences exhibited in society ls the result of trial and error. (Similar to the "efficient market theory" in the stock market.) Stan-conjectured that the risk of death from disease appears to determine a level of acceptable voluntary risk but that society requires a much lower level for involuntary risk. He noted that individuals seem to accept a much higher risk (by about 1000 times) if it is voluntary, e.g., sky-diving or mountain climbing, than if it is imposed, such as electric power or commercial air travel, by a correlating with the perceived benefit. From this study, a "law" of acceptable risk was found concluding that risk acceptability is proportional cube of the benefits. Figure 1.4.4-1 from Starr, 1972 shows these relationships. One aspect of revealed preferences is that these preferences do not necessarily remain constant (Starr et al., 1976). In Starr et al., 1976, it is shown that while nuclear power has the least risk of those activities compared, it also has the least perceived benefit. Clearly the public thinks that... 

Salem, S. L. et al., 1980, Issues and Problems in Inferring a Level of Acceptable Risk, R-2561-DOE, August. 

Fire and explosion are much more serious events than pollution. For one thing, fire and explosion can create catastrophes that will lead to poi ludon anyway, but for another thing, they can injure people. We clearl> want to have more levels of safety (that is, a lower probability of occurrence) in the chain leading to fire or explosion than is necessary in the chain leading to pollution. That is, whatever the acceptable risk lor <.)ii pollution, a lower risk is required for fire or explosion. 

Encouraging client and supplier companies to adopt similar risk management practices Selection of businesses with acceptable risks... 

The basis of RHT is set out in Figure 3.4. Individual levels of accepted risk are said to be determined by the costs and benefits of risky and cautious behavior, as set out in box a. 

Must have an acceptable "risk management program in place or undertake an "extraordinarily liazardous substance accident risk assessmeiU ... 

New Jersey also detailed what constituted as Acceptable Risk Management Program (RMP). It included ... 

Determine the action level in pg/iiv for an 80 kg person with a life expectancy of 70 years exposed to benzene over a 15-year period. The "acceptable risk is one incident of cancer per 1 million persons or lO ". Assume a breathing (intake) rate of 15 m /d and an absorption factor of 75%. The potency factor for benzene is 1.80 (mg/kg-d)." ... 

Zero sampling error Eq. (1.6) reduces to Vreprod = V repeat-Independent individual samples/measurements in the sense of Fig. 1.5. A result that is nearer to the SL(/ and an accepted risk of 5% (alpha/2 = 0.05 for the single-sided test use the alpha = 0.1 column in the t-table). 

Preclinical studies have suggested that early thrombolysis, within 3.5 hours of arterial occlusion, resulted in neurological improvement with an acceptable risk of secondary central nervous system hemorrhage. ... 

The basic tenets of the proposed policy is to encourage the manufacturer to reduce or eliminate the N-nitroso contaminant level in his product, or failing this to establish that the level does not exceed an "acceptable risk to the user of the pesticide or the general public. This latter process of evaluation also requires that the Agency consider the benefits of this pesticide together with the risk in order to reach a final decision. Since there might be hundreds of products falling under this policy, the... 

Acceptable Risk. Once information is assembled concerning the characteristics of exposure and biologic effects, that information must be interpreted in terms of human safety standards. That interpretation requires that one establish a set of criteria representing acceptably safe conditions for human existence, bearing in mind that zero concentrations of environmental chemicals are unrealistic. 

Table 89-1 summarizes the possible factors associated with prostate cancer.2 The only widely accepted risk factors for prostate cancer are age, race/ethnicity, and family history of prostate cancer.2 The disease is rare under the age of 40 years, but the incidence increases sharply with each subsequent decade, most likely because the individual has had a lifetime exposure to testosterone, a known growth signal for the prostate.3... 

For further reading on the subject of acceptable risk and risk management, see Cox and Tait (1998). 

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