Risk assessment safety factors

Risk assessment system For management to make enlightened safety and risk management decisions, accurate, timely risk assessment information must be provided. Risk assessment system factors to be evaluated include... 

Working accidents are often connected to structures collapse, damaged equipment or old working tools, absence of appropriate safety training and unrealistic risk assessment. These factors are very common in construction works such as excavation. 

In view of the above adverse effects a safety factor should be applied where flammability is assessed using flash point. For pure liquids in containers the vapor should be considered potentially flammable if the liquid temperature is upward of at least 5°C below the reported flash point. For mixtures whose composition is less certain, such as petroleum mixtures, the safety factor should be about 15°C relative to the flash point [55]. Where combinations of adverse effects are identified the safety factors should be increased accordingly. A simple but very conservative approach is to assume that all liquids having a flash point <141°F may produce a flammable atmosphere under some ambient conditions, even where no mist or froth production is involved. A more practical approach is to assume that liquids handled in air at least 5-15°C below their closed cup flash points will not present ignition risks unless... 

A company produced bromine in Arkansas and brominated compounds in New Jersey. A risk assessment resulted in a recommendation to consider the transfer of the bromination processes to the bromine production site in Arkansas. Economics and the decrease in risk justified such a transfer and it was done. Although safety was not the only consideration, it was an important factor in this decision. 

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-... 

Performance-influencing factors analysis is an important part of the human reliability aspects of risk assessment. It can be applied in two areas. The first of these is the qualitative prediction of possible errors that could have a major impact on plant or personnel safety. The second is the evaluation of the operational conditions under which tasks are performed. These conditions will have a major impact in determining the probability that a particular error will be committed, and hence need to be systematically assessed as part of the quantification process. This application of PIFs will be described in Chapters 4 and 5. 

Banks, W., Wells, J. E. (1992). A Probabilistic Risk Assessment Using Human Reliability Analysis Methods. In Proceedings of the International Conference on Hazard Identification and Risk Analysis, Human Factors, and Human Reliability in Process Safety. New York American Institute of Chemical Engineers, CCPS. 

This gives an example of fate modeling in which the risks of an insect growth inhibitor, CGA-72662, in aquatic environments were assessed using a combination of the SWRRB and EXAMS mathematical models.. Runoff of CGA-72662 from agricultural watersheds was estimated using the SWRRB model. The runoff data were then used to estimate the loading of CGA-72662 into the EXAMS model for aquatic environments. EXAMS was used to estimate the maximum concentrations of CGA-72662 that would occur in various compartments of the defined ponds and lakes. The maximum expected environmental concentrations of CGA-72662 in water were then compared with acute and chronic toxicity data for CGA-72662 in fish and aquatic invertebrates in order to establish a safety factor for CGA-72662 in aquatic environments. 

Aquatic safety factors ranged from 5.5 X 107 for rainbow trout in ponds to 9.3 X 108 for daphnia in lakes. These data emphasize that exposure levels of CGA-72662 are low and must be taken into account for a risk assessment. Although the persistence of CGA-72662 in eutrophic lakes is relatively long, the exposure is extremely low and of no environmental consequence. Overall, use of SWRRB runoff and EXAMS models show CGA-72662 to be very safe in aquatic habitats when used on vegetables in Florida muck soil. 

The systematic evaluation of substance properties and predictable or actual exposure patterns over the entire life-time of a substance within the scope of risk assessment is as yet a relatively recent instrument, for which harmonised scientific rales were created in the EU for the first time in 1997 in the form of the Technical Guidance Documents (TGD). An essential element in this range of instruments is how to deal with shortcomings in knowledge. Wherever information is missing, standardised worst-case scenarios are conceived taking into account appropriate safety factors . If under these worst-case assumptions a rele-... 

The question of an extra assessment factor in the hazard and risk assessment for chemicals of concern for children is specifically addressed in Section 5.2.1.13. The U.S. Food Quality Protection Act (FQPA) (US-EPA 1996) directed the US-EPA to apply an extra safety factor of 10 in assessing the risks of pesticides to infants and children. The US-EPA (2002) noted the overlap of areas covered by the FQPA factor and those addressed by the traditional UFs, and it was concluded that an additional UF (children-specific) is not needed in the setting of reference values because the currently available UFs (interspecies, intraspecies, LQAEL-to-NOAEL, subchronic-to-chronic, and database-deficiency) were considered sufficient to account for uncertainties in the database from which the reference values are derived. Renwick et al. (2000) concluded that the available data did not provide a scientific rationale for an additional 10-fold UF for infants and children and pointed out that when adequate reproduction, multigeneration, or developmental studies are conducted, there will be no need for an additional 10-fold factor. 

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