Risk assessment methods

Qualitative approaches typically easier to apply but provide the least degree of insight. Conversely quantitative risk analysis (QRA) approaches are most demanding on resources and skill sets, but potentially deliver the most detailed understanding and provide the best basis if significant expenditure is involved. Semiquantitative approaches lie in between these extremes. The following sections will describe briefly some of the techniques that have been used in the context of corrosion risk assessment. 

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P. A. Fenner-Crisp, "Risk Assessment Methods for Pesticides in Food and Drinking Water," Office of Pesticide Programs, U.S. Environmental Protection Agency, presented at the Florida Pesticide Review Council Meeting, July 7, 1989. 

Research is needed on developing the triggers to move from one hazard tier to the next and on risk assessment methods. 

Core damage and containment performance was assessed for accident sequences, component failure, human error, and containment failure modes relative to the design and operational characteristics of the various reactor and containment types. The IPEs were compared to standards for quality probabilistic risk assessment. Methods, data, boundary conditions, and assumptions are considered to understand the differences and similarities observed. 

Another problem of EGAs is that they are non-site-specific. The reasons for this lie in the fact that they include the whole life cycle of systems with resources which may originate in different countries and waste products and emissions which may distribute globally. They deal with factual inputs, outputs and the environmental impact potentials of the system under investigation on a global, and, in some cases, regional scale. Yet, they do not address the intrinsic risks resulting from the system itself. However, a combination with risk assessment methods can be used to close this gap. 

As probabilistic exposure and risk assessment methods are developed and become more frequently used for environmental fate and effects assessment, OPP increasingly needs distributions of environmental fate values rather than single point estimates, and quantitation of error and uncertainty in measurements. Probabilistic models currently being developed by the OPP require distributions of environmental fate and effects parameters either by measurement, extrapolation or a combination of the two. The models predictions will allow regulators to base decisions on the likelihood and magnitude of exposure and effects for a range of conditions which vary both spatially and temporally, rather than in a specific environment under static conditions. This increased need for basic data on environmental fate may increase data collection and drive development of less costly and more precise analytical methods. 

A Case Study Advancing Ecological Risk Assessment Methods in the EPA, Office of Pesticide Programs, Final Report from FIFRA Scientific Advisory Panel. USEPA, Washington, DC (2001). Also available on the World Wide Web http //www.epa.gov/scipoly/sap 001/index.htm, accessed September 2002. 

In the following exposition, we will describe the exposure and risk assessment methods in four major steps (See Figure 1) ... 

Volume I primarily provides an outlook at various industrial sectors and the additives applied therein, whereas in the second volume, two risk assessment methods are presented and recommendations for further research activities are discussed. 

Government risk assessment methods used to determine acceptable residues in foods (governed by tolerances) were not designed to detect or quantify the majority of these unique risks. 

EPA research investments since 1995 in pesticide exposure and risk assessment methods have helped pioneer novel approaches to quantify risk levels. A team at the University of Washington s School of Public Health and Community Medicine found that 2-5 year olds consuming predominantly organic foods over a 3-day period had 8.5-fold lower mean levels of OP insecticide metabolites in their urine than children eating mosdy conventional (unlabeled) foods (Curl et al., 2003). The study was carefully designed to minimize potentially... 

This keynote paper gives a general discussion of blast waves developed by high explosive detonations, their effects on structures and people, and risk assessment methods. The properties of free-field waves and normally and obliquely reflected waves are reviewed. Diffraction around block shapes and slender obstacles is covered next. Blast and gas pressures from explosions within vented structures are sumnarized. 

The primary document outlining risk assessment methods in the U.S. Department of Defense is a Military Standard, Ref. 39. This document requires a well-documented system safety program, based on risk assessment methods to be included in all new Department of Defense systems and facilities. Hazards analyses of the systems are mandated by this publication. 

In Ref. 42, we see a review of the risk assessment methods used in Switzerland, and an application to assessing risks in solid propellant production. In the Swiss methods, one first defines individual risk r, as... 

In use of risk assessment methods, you will find that the methodology for calculating overall risk probabilities is quite well defined. But, assigning realistic values to individual probabilities can be quite difficult, and a matter of personal opinion of the analyst. So, the analyst must have intimate knowledge of the system being evaluated, as well as all effects being considered, before he can make an acceptable risk assessment. 

Figure 37. Risk Matrix for Swiss Risk Assessment Methods. (Ref. 42)...

Additives are used in foods to perform a variety of functions, many of which are described elsewhere in this book. The use of additives is intended to provide some benefit to the consumer such as improved shelf life, taste or texture. However, where additives are used in foods, the public is entitled to expect that they will not be exposed to unacceptable risks should they consume such foods. This chapter is devoted to describing risk assessment methods that are applied at national and international levels. 

The liquid and solid effluents are well characterized. As the ACW I Committee noted in its original and supplemental reports, the gaseous process emissions will have to be characterized for health risk assessments and environmental risk assessments required by EPA guidelines (NRC, 1999, 2000a). These results, along with the results of analyses of metals emissions (including chromium VI), can be used to assess the environmental impact of a facility through accepted risk-assessment methods (EPA, 1998). 

Risk Assessment—methods. 4. Risk Assessment—standards. WA 670 0845p 2008]... 

ECOFRAM] Ecological Committee on FIFRA Risk Assessment Methods. 1999. ECOFRAM Terrestrial Draft Report. Ecological Committee on FIFRA Risk Assessment Methods. 

In summary, in studies of chemical toxicity, pathways and rates of metabolism as well as effects resulting from toxicokinetic factors and receptor affinities are critical in the choice of the animal species and experimental design. Therefore it is important that the animal species chosen as a model for humans in safety evaluations metabolize the test chemical by the same routes as humans and, furthermore, that quantitative differences are considered in the interpretation of animal toxicity data. Risk assessment methods involving the extrapolation of toxic or carcinogenic potential of a chemical from one species to another must consider the metabolic and toxicokinetic characteristics of both species. 

Human health risk assessment has often been dominated by the use of default assumptions and worst case analyses, based on the use of upper bounds on the dose from exposure instead of distributional characterizations of that dose. There are severe limitations associated with the use of default assumptions and upper bounds instead of distributions when detailed exposure and/or dose-response data are available. The US National Academy of Sciences, the USEPA, and many others have recognized the need for new risk assessment methodology (NRC, 1983, 1993, 1994 USEPA, 1992 CRARM, 1997). This need has promoted the development of new quantitative risk assessment methods that use probabilistic techniques, especially Monte Carlo simulation and distributional characterizations of dose-response, exposure, and risk. For these reasons, this paper uses a probabilistic approach. An indication of some of these new methods and the type of results they produce are given below. 

Suter et al. 1993 Society of Environmental Toxicology and Chemistry [SETAC] 1994 European Union 1997 Ecological Committee on FIFRA Risk Assessment Methods [ECOFRAM] 1999 Campbell et al. 1999). The initial use of conservative assessment criteria (i.e., err on the side of caution) allows substances that do not present a risk to be eliminated from the risk assessment process early, thus allowing the focus of resources and expertise to be shifted to potentially more problematic substances or situations. As one ascends through the tiers, the estimates of exposure and effects become more realistic with the acquisition of more accurate and/or representative data, and uncertainty in the extrapolation of effects is thus reduced or at least better characterized. Likewise, the methods of extrapolation may become more sophisticated as one ascends through the tiers (Figure 1.2). 

Extrapolation methods are used for various types of risk assessment. Methods may be used in the process of deriving environmental quality objectives, in the registration of new substances, and in the process of site-specific risk assessment. Suter (1993) called these approaches prospective (the former 2) and retrospective (the latter) risk assessments. The specific process in which extrapolation methods are used has implications for the concepts to be applied and the data to be used as input in extrapolation. Strictly described approaches are in place for the derivation of environmental quality criteria (EQCs) and the registration of pesticides and newly developed substances. The prescribed approaches for deriving EQCs can differ between jurisdictions. The approaches for retrospective investigations have more degrees of freedom. A characteristic of the latter approach is that the methods can make use of measured local exposure levels and can estimate local risk with known precision (or known uncertainty ). The latter is uncommon for EQCs. 

Brock TCM, Crum SJH, Deneer JW, Heimbach F, Roijackers RMM, Sinkeldam JA. 2004. Comparing aquatic risk assessment methods for the photosynthesis-inhibiting herbicides metribuzin and metamitron. Environ Pollut 130 403-426. 

Krishnan K, Paterson J, Williams DT. 1997. Health risk assessment of drinking water contaminants in Canada the applicability of mixture risk assessment methods. Reg Toxicol Pharmacol 26 179-187. http //www.ncbi.nlm.nih.gov/entrez/query.fcgi7cm d=Retrieve db=PubMed dopt=Citation list uids=9356281 (accessed December 28, 2007). 

Teuschler LK, Rice GE, Wilkes CR, Lipscomb JC, Power FW. 2004. A feasibility study of cumulative risk assessment methods for drinking water disinfection by-product mixtures. Journal of Toxicology and Environmental Health Part A 67 755-777. 

DNLM 1. Environmental Monitoring-methods. 2. Models, Biological. 3. Risk Assessment—methods. WA 670 E9842008]... 

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