Marginal risks

Tasks with high risk are given a higher priority and may require immediate actions. A step may, on the other hand, include tasks with only marginal risk and have limited safety requirements. If a job step is shown to have catastrophic potential, the job is immediately shut down until the risk is brought to an acceptable level with immediate controls implemented. 

To lessen the risk of pumping sludges or slurries into a unit, the practice is to leave a safety margin of 50 cm (heel) below the outlet nozzle or install a strainer on the pump suction line. The deposits accumulate with time and the tanks are periodically emptied and cleaned. 

Maximum Contaminant Level Goal (MCLG) - The level of a contaminant in drinking water below which there is no known or expected risk to health. MCLGs allow for a margin of safety and are non-enforceable public health goals. 

The first step-in plant-system and accident-sequence analysis is the identification of earthquake-induced initiating events. This is done by reviewing the internal analysis initiating events to identify initiating events relevant to seismic risk. For example. Table 5,1 -5 shows the initiating events that were used in the Seismic Safety Margins Research Program for a PWR plant (Smith et al., 1981)... 

In risk characterization, step four, the human exposure situation is compared to the toxicity data from animal studies, and often a safety -margin approach is utilized. The safety margin is based on a knowledge of uncertainties and individual variation in sensitivity of animals and humans to the effects of chemical compounds. Usually one assumes that humans are more sensitive than experimental animals to the effects of chemicals. For this reason, a safety margin is often used. This margin contains two factors, differences in biotransformation within a species (human), usually 10, and differences in the sensitivity between species (e.g., rat vs. human), usually also 10. The safety factor which takes into consideration interindividual differences within the human population predominately indicates differences in biotransformation, but sensitivity to effects of chemicals is also taken into consideration (e.g., safety faaor of 4 for biotransformation and 2.5 for sensitivity 4 x 2.5 = 10). For example, if the lowest dose that does not cause any toxicity to rodents, rats, or mice, i.e., the no-ob-servable-adverse-effect level (NOAEL) is 100 mg/kg, this dose is divided by the safety factor of 100. The safe dose level for humans would be then 1 mg/kg. Occasionally, a NOAEL is not found, and one has to use the lowest-observable-adverse-effect level (LOAEL) in safety assessment. In this situation, often an additional un-... 

The draft risk due to cold air pillows under the roof glazing dropping into the occupied zone was determined by transient CFD calculations. As can be seen from Fig. 11.57, velocities do not exceed 0.2 m/s. Therefore, the draft risk was assumed to be marginal. 

Table 18.4.1 smiinuuizes another inetliod of risk assessment tliat can be applied to an accident system failure. Both probability and consequence have been ranked on a scale of 0 to 1 witli table entries being the sum of probability and consequence. The acceptability of risk is a major decision and can be described by dividing tlie situations presented in Table 18.4.1 into unacceptable, marginally acceptable, and acceptable regions. Figiue 18.4.2 graphically represents tliis risk data. ... 

The magnitude of the safety factor is very important and usually ranges from 1.4 to 2.8 depending upon downhole conditions, drill pipe quality and acceptable degree of risk. It is recommended that a value of safety factor be selected to produce a margin of overpull of at least about 70,000 lb. 

The simplest form of pressurization uses the expansion of the water content of the system to create a sufficient pressure in an expansion vessel to provide an anti-flash margin of, say, 17°C at the lowest pressure (highest point) of the system. The main disadvantage of a naturally pressurized expansion vessel is the ability of water to absorb air and the consequent risk of oxygen corrosion. 

During the implementation of the improvement, money is spent, and debt is incurred, offset by operating margin as it improves. Interest is paid at intervals on the outstanding balance, and after a suitable payback time—which is shorter, the better the improvement—all the debt is recovered, and a better operation is running. This graph then gives three crucial pieces of information, viz. (a) the maximum risk in the form of new... 

Susceptibility in the context of pharmacogenetics is a marginally to moderately increased risk for a disease. 

The sheer complexity of environmental mixtnres of EDCs, possible interactive effects, and capacity of some EDCs to bioaccumulate (e.g., in fish, steroidal estrogens and alkylphenolic chemicals have been shown to be concentrated up to 40,000-fold in the bile [Larsson et al. 1999 Gibson et al. 2005]) raises questions about the adequacy of the risk assessment process and safety margins established for EDCs. There is little question that considerable further work is needed to generate a realistic pictnre of the mixture effects and exposure threats of EDCs to wildlife populations than has been derived from studies on individual EDCs. Further discussion of the toxicity of mixtures will be found in Chapter 2, Section 2.6. 

To calculate the safe re-entry interval (REI), the margin of exposure (MOE) must be considered. Worker risk is measured as a margin of exposure and is related to how closely the occupational exposure comes to the no observed adverse effect level (NOAEL, for oxamyl 50 mg kg day ). MOE is defined as... 

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