Uncertainties in risk assessment

Uncertainty analysis is increasingly used in ecological risk assessment and was the subject of an earlier Pellston workshop (Warren-Hicks and Moore 1998). The US Environmental Protection Agency (USEPA) has developed general principles for the use of Monte Carlo methods (USEPA 1997), which provide one of several approaches to incorporating variability and uncertainty in risk assessment. 

It is therefore important to take account of variability and uncertainty in risk assessment. The question is, how ... 

Hoffman FO, Hammonds IS. 1994. Propagation of uncertainty in risk assessments the need to distinguish between uncertainty due to lack of knowledge and uncertainty due to variability. Risk Anal 14 707-712. 

A 2nd critical addition when planning a probabilistic assessment is the choice of methods for propagating variability and nncertainty. The workshop reviewed a range of contrasting methods of analyzing uncertainty in risk assessments ... 

Bayesian approaches are discussed throughout this book. Unfortunately, because frequentist methods are typically presented in introductory statistics courses, most environmental scientists do not clearly understand the basic premises of Bayesian methods. This lack of understanding could hamper appreciation for Bayesian approaches and delay the adaptation of these valuable methods for analyzing uncertainty in risk assessments. 

EXAMPLES RELEVANT TO UNCERTAINTY IN RISK ASSESSMENT QUANTIFYING PLAUSIBILITY OF A CAUSE-EFFECT MODEL... 

Uncertainties in risk assessment include considerations related to missing, incomplete and/or incorrect knowledge, as well as those associated with ignorance and/or lack of awareness. Uncertainties should be characterized as transparently as possible to ensure their adequate consideration in decision-making concerning the need for and nature of appropriate risk management and communication. 

In the practice of soil and sediment analysis, bioassays often are used in conjunction with chemical analysis and ecological field observations. This approach, named the TRIAD approach, was first introduced for sediment analysis by Chapman (1986) and is becoming more common for contaminated land assessment (Jensen and Mesman 2006). Such multimetric methods allow for reduction of uncertainties in risk assessment as evaluation is based on several independent lines of evidence (Chapman et al. 2002). 

Uncertainty in Risk Assessments of Potential PBT/vPvB Substances... 

Risk assessment evaluates risk in terms of hazard and exposure, but reference to risk levels must account for different perceptions of risk as well as scientific uncertainties in risk assessment. In short, this research project considers the importance of social and institutional processes in influencing risk perceptions and risk acceptability. This book therefore takes a constrained relativist approach by incorporating risk perceptions in the research framework. An unconstrained relativist perspective would imply that no scientific study is reliable or robust. By contrast, a constrained relativist approach can provide a useful basis for examining the different social and cultural factors involved in regulatory risk management. 

Quantifying Uncertainty in Risk Assessment Practical Approaches and their Application to Estimating Ecological Risks of Pesticides , report on the findings of a workshop held in Pensacola, FL, USA., SET AC, February 24 to March 1,2002 (in preparation). 

Interspecies and intraspecies UFs have been used in the development of safe or threshold exposure levels for chronic, noncancer toxicity by health organizations throughout the world. Examples include the acceptable daily intake (ADI) (Lu 1988 Truhaut 1991 Lu and Sielken 1991), the tolerable daily intake (TDI) or tolerable concentration (TC) (Meek et al. 1994 IPCS 1994), the minimal risk level (MRL) (Pohl and Abadin 1995), the reference dose (RfD) (Barnes and Dourson 1988 Dourson 1996), and the reference concentration (RfC) (EPA 1994 Jarabek et al. 1990). The importance of using distribution-based analyses to assess the degree of variability and uncertainty in risk assessments has been emphasized in recent trends in risk analysis. This will enable risk managers to make more informed decisions and... 

Sources of Uncertainties in Risk Assessment Table 4 Slope factors of some common hazardous compounds. 13... 

Lack of data is often a signihcant source of uncertainty in risk assessments. Unavailable data may include source concentrations or source contaminants such as those not quantihed by standard analyses such as EPA methods 624 and 625. RfDs and SFs are currently only available for fewer than two hundred chemicals however, since thousands of chemicals are potentially present at contaminated sites and hazardous waste facilities, the paucity of available data may be responsible for a significant amount of uncertainty. 

A conventional way of addressing uncertainty in risk assessments is to estimate and assign reasonable worst-case conditions for our evaluations or models. Thus, in this case one would typically pick the worst case (highest G and lowest Q) to estimate a worst case for C. Next, this could then be combined with best case estimates (lowest G and highest Q) to provide a range for C. Finally, the impact or sensitivity of G or Q on either best or worst-case scenarios could be determined by calculating the results of varying these predictors from maximum to minimum individually in each. 

Science policy issues and controversies underlie almost every aspect of cancer risk assessment. These policy issues are primarily a function of the scientific uncertainties inherent in risk assessment. As new scientific methods and data begin to fill in some of the data gaps and uncertainties in risk assessment, the role of policy will gradually recede, although there is no prospect of policy issues being mooted entirely in the foreseeable future. Moreover, the extent to which we substitute novel scientific data and models for preexisting policy inferences is itself an ongoing policy debate, as is the appropriate role of precaution and conservatism in risk assessment. 

McClellan, R. O. (1996). Reducing uncertainty in risk assessment by using specific knowledge to replace default options. Drug Metab Rev 28, 149-179. 

Pleil, J. D., Kim, D., Prah, J. D., and Rappaport, S. M. (2007). Exposure reconstruction for reducing uncertainty in risk assessment Example using MTBE biomarkers and a simple pharmacokinetic model. Biomarkers 12, 331-348. 

ORD is a leader in environmental research, focusing its efforts and resources on those areas in which EPA can add the most value to reducing uncertainty in risk assessments and enhancing environmental risk management. 

Use of site-specific As bioavailability data in risk assessment may dramatically lower cleanup costs. The demand for site-specific soil bioavailability data will likely increase because in vivo and in vitro bioavailability methods are inexpensive compared with site cleanup based on overly conservative soil bioavailability As levels. Site-specific As availability information will lower the degree of uncertainty in risk assessment and provide scientifically derived data to aid in the selection of appropriate remedies that are cost effective and protective of human health and the environment. 

Aven, T. Zio, E. 2011 Some Considerations on the Treatment of Uncertainties in Risk Assessment for Practical Decision Making. Reliability Engineering and System Safety, 96, 64—74. 

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