Risk Assessment in the Federal Government Managing the Process (1983) / Chapter Skim
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1 The Nature of Risk Assessment
1 The Nature of Risk Assessment
Pages 17-50
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From page 17... ...
Our obj ective was to examine whether alterations in institutional arrangements of Procedures, particularly the organizational separation of Disk assessment from regulatory decisionrmaking and the use of uniform guide lines for inferring risk from available scientific ~nformation, can improve federal risk assessment activities. Before undertaking to determine whether organizational and procedural reforms could improve the performance and use of risk assessment in the federal government, the Committee examined the state of risk assessment and the regulatory environment in which it is performed.
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From page 18... ...
Risk assessments include several elements: description of the potential adverse health effects based on an evaluation of results of epidemiologic, clinical, toxicologic, and env~ro~ental research; extrapolation from those results to predict the type and estimate the extent of health effects in humans under given conditions of exposure; judgments as to the number and characteristics of persons exposed at various intensities and durations and summary judgments on the existence and overall magnitude of the p~li~health problem. Risk assessment also includes characterization of the uncertainties inherent in the process of inferring risk .
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From page 19... ...
S'~:~S IN RISK AS SESSME:NT Risk assessment can be divided into four major steps: hazard zOentif ication, dose-response assessment, exposure assessment, and risk characterization. A risk assessment might stop with the first step, hazard identification, if no adverse effect is found or if an agency elects to take regulatory action without further analysis, for reasons of policy or statutory mandate.
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From page 20... ...
Exposure assessment is often used to identify Feasible prospective control options and to predict the effects of available control technologies on exposure. ~~L china -~515~ is the process of estimating the incidence of a health effect under the various colons of human exposure described in exposure assessment.
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From page 22... ...
Thus, epidemiologic data require careful interpretation. Even if these problems are solved satisfactorily, the preponderance of chemicals in the environment has not been studied with epidemiologic methods, and we would not wish to release newly produced substances only to discover years later that they were powerful carcinogenic agents.
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From page 23... ...
Comparisons of Molecular Structure Comparison of an agent's chemical or physical properties with those of known carcinogens provides some evidence of potential carcinogenicity. Experimental data support such associations for a few structural classes; however, such studies are best used to identify potential carcinogens for further investigation and may be useful in priority-setting for carcinogenicity testing.
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From page 24... ...
24 to corroborate hazard identif ication, that is, to show that the agent does indeed induce the adverse health effect. The testing of chemicals at high doses has been challenged by soree scientists who argue that metabolism of chemicals differs at high and low doses; i.e., high doses may overwhelm normal detoxification mechanists and provide results that would not occur at the lower doses to which humans are exposed.
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From page 25... ...
dose of.a given carcinogen) there is no adverse effect.
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From page 26... ...
26 lo-2 10-4 ~s C~ A ~ 10 6 6 cr: X Lo 10-8 / /Subl Sneer ~ I 10 lo | 1 0.01 i' Supralinear '~7 I ~ / 0.1 Sublinear I | Threshold I 1 1.0 10.0 DOSE (,uglweek) FIGURE I-2 Results of alternative extrapolation models for the same experimental data.
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From page 27... ...
S ten 3. Exposure Assessment The f ~ rst task of an exposure assessment is the determiner tion of the concentration of the chemical to which humans are exposed.
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From page 28... ...
The Importance of exposures to a mixture of carcinogens is another factor that needs to be considered in assessing human exposures. For example, exposure to c~garette smoke and asbestos g ives an incidence of cancer that is much greater than anticipated from carcinogen~city data on each substance individually.
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From page 29... ...
· Should a study be weighted according to its quality and statistical power? · Bow should evidence of different metabolic pathways or vastly different metabolic rates between animals and hams be factored into a risk assessment?
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From page 30... ...
· What degree of confidence do short-term tests add tootle results of animal bioassays in the evaluation of carcinogenic risks for butane? · Should in vitro transformation tests be accorded more weight than bacterial mutagenicity tests in seeking evidence of ~ possible carcinogenic effect?
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From page 31... ...
· For what range of health effects should responses be tabulated? For example, should risk estimates be made only for Specific types of cancer that are unequivocally related to exposure, or should they apply to all types of cancers?
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From page 32... ...
* Current methods and approaches to exposure assessment appear to be mediums or route-specific.
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From page 33... ...
One component of risk assessment is the decision as to whether to use experimental animal data to infer risks to humans. Although data from studies of rats and mice may not always be predictive of adverse health effects in humans, the scientific validity of this approach is widely accepted.
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From page 34... ...
Some benign tumors probe ably can progress to malignant lesions and some probably do not. The judgment that benign tumors and malignant tumors should be counted equally will affect tumor incidence and may influence the yes-no determination in hazard identification, and it can also affect the doseresponse relation by increasing incidence at the doses tested.
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From page 35... ...
In contrast with hazard identification and dose-response assessment, exposure assessment has very few components that could be applicable to all media. For example, a model describing transport of a chemical through the atmosphere is necessarily quite different from a model describing transport through water or soil, whereas the use of a particular dose~response extrapolate tion model in dose-response assessment is independent of the medium or route of exposure.
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From page 36... ...
Little guidance is available on how JO express uncertainties in the underly~ng data and on which dose-response assessments and exposure assessments should be combined to give a final estimate of possible risk. Basis for Selecting Inference Outions The Committee has presented some of the more familiar, and possibly more controversial, components of risk assessment.
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From page 37... ...
Such judgments made in risk assessment are designated risk assessment police, that is, policy related to and subservient to the scientific content of the process, in contrast with policy invoked to guide risk management decisions, which has political, social, and economic determinants. When inference options are chosen primarily on the basis of policy, risk management considerations (the desire to regulate or not to regulate)
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From page 38... ...
Risk Management. Risk management is the process of evaluating alternative regulatory options and selecting among them.
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From page 39... ...
Chemicals that are judged to present appreciable risks to health are candidates for regulatory action, and an agency will begin to develop options for regulating expose surest Regulatory options usually invol ve specif ic product or process changes and typically need to }>e based on extensive engineering and technical knowledge of the affected industry. Evaluation of the regulatory options includes recomputation of the predicted risk, in accord with altered expectations of exposure intensity or numb bers of persons exposed.
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From page 40... ...
These varied functions place different requirements on risk assessors, and a single risk assessment method may not be sufficient. A risk assessment to establish testing priorities may appropriately incorporate many worst-case assumptions if there are data gaps, because research should be directed at substances with the most crucial gaps; but such assumptions may be inappropriate for analyzing regulatory controls, particularly If the regal later must ensure that controls do not place undue strains on the economy.
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From page 41... ...
This division reflects a conscious congressional choice in 1970 to place ache health experts on whom OSEA was expected to rely in an outside environment believed more congenial to scientific inquiry and less vulnerable to political influence. As of 1981, 18 potential carcinogens had been acted on by OSEA.
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From page 42... ...
, which formed a work group on risk assessment to develop a guides line for assessing carcinogenic risks. Assisted by scientists from the National Cancer Institute and the National Institute for Environmental Health Sciences, it examined the various approaches used by the four agencies to evaluate evidence of carcinogenicity and to assess risk.
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From page 43... ...
The most important effect of this difference may lie in the fact that premarketing approval programs (such as those for pesticides, for new human drugs, and for new food additives empower an agency to require the submission of sufficient data for a comprehens~ve risk assessment, whereas other programs tend to leave agencies to fend for themselves in the acquisition of necessary data. There can be little question that differing statutory standards for decision affect the weight that agencies accord risk assessments.
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From page 45... ...
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From page 47... ...
47 ~ ~ v ' ~ ° co ~ 5 E E C| ..
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From page 48... ...
The Committee believes that much of this criticism is inappropriately directed and gives rise to an unrealistic expectation that modifying risk assessment procedures will result in regulatory decisions more acceptable to the critics. Certainly risk assessment can and should be Improved, with salutary effects on the appropriateness of regulatory decisions.
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From page 49... ...
The lay i should not be allowed to control the former, risk assessment Policv. Risk management policy, by its very nature, must entail value judgments related to public perceptions of risk and to information on risks, benefits, and costs of control strategies for each substance considered for regulation.
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From page 50... ...
44 :39858. IREG (Interagency Regulatory Liaison Group)
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Key Terms
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