Risk assessment, problems

Defining the risk assessment problem to be evaluated should precede entering the four-step process set out in Figure 7.1, Chapter 7. This means identifying the population that is to be the subject of the assessment, and specifying the conditions under which it is or may come to be exposed to a chemical or mixture of chemicals. Formulations of the problem might be similar to any of the five examples offered at the beginning of Chapter 7. 

An array of extrapolation methods is needed and available to solve a diversity of ecological risk assessment problems. 

It is evident that some techniques do not have conceptually similar equivalents with various levels of complexity. Hence, tiering is not (yet) possible for all problem definitions. Moreover, it is clear that human risk assessment can sometimes operate on a higher conceptual tier than ecological risk assessment, for example, when BRN modeling and PBPK models are used. On the other hand, ecological risk assessment approaches may be sometimes more diverse, and can be better tailored to a risk assessment problem and its context. 

Unfortunately a very substantial fraction of the quantitative risk assessment problems of concern today fall into categories 3, or 5 of this classification. 

Giyen a risk assessment problem that inyolyes uncertainty in the yalue of model coefficients there are a variety of analytical strategies t lch an analyst can adopt. These Include ... 

Mitchell CL, Tilson HA (1982) Behavioral toxicology in risk assessment problems and research needs. CRC Crit Rev Toxicol 10 265-274... 

Before leaving tliis introductory section, tlie reader is again reminded of tlie difference between healtli risk assessment (HRA) and liazard risk assessment (H2RA). Unfortunately, both terms have been used interchangeably by researchers and industrial persomiel. As indicated above, tliis Part of tlie book will address chronic health problems (HRA) while Part IV and V will be primarily on acute health problems (HZRA),... 

An appropriate sampling program is critical in the conduct of a hcaltli risk assessment. This topic could arguably be part of the exposure assessment, but it has been placed within hazard identification because, if the degree of contamination is small, no further work may be necessary. Not only is it important that samples be collected in a random or representative manner, but the number of samples must be sufficient to conduct a statistically valid analysis. The number needed to insure statistical validity will be dictated by the variability between the results. The larger the variance, tlic greater the number of samples needed to define tire problem, ... 

Human health risk assessment estimates the likelihood of health problems occurring if no cleanup action were ttikcn at the site. To cstiimite the baseline risk at a site, the following four-step process should be taken to detennine Uie possible human risk which will then detennine what sort of corrective action should be employed ... 

Lay people and experts disagree on risk estimates for many eiivironincntal problems. This creates a problem, since die public generally does not trust the experts. This chapter concentrates on how the public views risk and what the future of public risk perception will be. The reader should note that much of diis material, as with die previous Section, applies to liazard risk assessment- a topic that is treated in Chapter 19, Ptirt IV. 

Tlie reader should also note that tlie risk to people can be defined in terms of injury or fatality. The use of injuries as a basis of risk evaluation may be less disturbing tlian tlie use of fatalities. However, tliis introduces problems associated with degree of injury and comparability between different types of injuries. Further complications am arise in a risk assessment when dealing witli multiple hazards. For example, how are second-degree bums, fragment injuries, and injuries due to toxic gas e.xposure combined Even where only one type of effect (e.g., tlueshold to.xic exposure) is being evaluated, different durations of e.xposure can markedly affect tlie severity of injury. 

D. Hendershot, "A Simple Example Problem Illustrating tlie Methodology of Chemical Process Quantitative Risk Assessment," paper presented at AICliE Mid-Atlantic Region "Day in Industry" for Chemical Engineering Faculty, Apr. 15, 1988. 

This book is divided into five parts the problem, accidents, health risk, hazard risk, and hazard risk analysis. Part 1, an introduction to HS AM, presents legal considerations, emergency planning, and emergency response. This Part basically ser es as an oveiwiew to the more teclmical topics covered in the remainder of the book. Part 11 treats the broad subject of accidents, discussing fires, explosions and other accidents. The chapters in Parts 111 and Part IV provide introductory material to health and hazard risk assessment, respectively. Pai1 V examines hazaid risk analysis in significant detail. The thiee chapters in this final part include material on fundamentals of applicable statistics theory, and the applications and calculations of risk analysis for real systems. 

The following sections will attempt to look ahead to likely fntnre problems with organic pollntion, to probable changes in the ways in which it is stndied and monitored, and in the tests and strategies used for environmental risk assessment of organic chemicals. 

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