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DEALING WITH UNCERTAINTY ABOUT RISK IN RISK MANAGEMENT 53 original typesetting files. Page breaks are true to the original; line lengths, word breaks, heading styles, and other typesetting-specific formatting, however, cannot be About this PDF file: This new digital representation of the original work has been recomposed from XML files created from the original paper book, not from the retained, and some typographic errors may have been accidentally inserted. Please use the print version of this publication as the authoritative version for attribution. of calibrating these experiments. A second consideration, suggested by animal test results (Haseman, 1983), is whether certain carcinogens redistribute the tumor burden whereas others increase the incidence of tumors. If this turns out to be the case, it may be beneficial to discriminate between the two types of effect. Conservative assumptions about risk are thought to provide protection against uncertainty in risk, although sometimes at an added cost. Much impetus for analytical conservatism derives from the belief that this practice protects health. This is the perspective when risks are viewed singly. But conservatism may not protect if reduced exposure to uncertain risks is achieved at the expense of increased exposure to known risks. Considering the many ways in which a conservative analysis can fail to protect, intentional use of conservative risk estimates is not beneficial to public health. In addition to misallocating scarce resources, conservatism can lead to unwise risk transfers and encourage risk regulators to compensate for perceived conservatism. When this happens, risk regulation becomes less predictable and more arbitrary. DE MINIMIS RISK* The term de minimis is used in law to describe trivial issues not deserving of a court's time and attention. When applied to health and safety risks and their regulation, the term refers to a risk that avoids regulatory attention by virtue of its small size. This concept has several potential regulatory applications. A de minimis rationale can be used either to determine the regulatory standard or to decide that no standard is required. In the latter case, whole classes of small risks may be excluded from regulatory consideration. In addition, de minimis may be the basis for an enforcement decision, as when a policeman decides not to cite a driver for exceeding the speed limit by one mile per hour. The impetus to establish a consistent de minimis approach to risk regulation has increased in recent years for several reasons. First, technologies for identifying risks have improved in several ways. Improvements in analytical chemistry permit the detection of hazardous substances at the part-per-billion or even part-per-trillion level; only a decade ago such exposures would have been ignored simply because they would have been undetectable. (Radiation is an exception to this rule, since it has been detectable at low levels for decades. This helps to explain why many de minimis proposals have arisen from the radiation protection area.) * This section is derived from C. Whipple, ''Application of the De Minimis Concept in Risk Management.'' Paper presented at a joint session of the American Nuclear Society and Health Physics Society, New Orleans, June 6, 1984.
DEALING WITH UNCERTAINTY ABOUT RISK IN RISK MANAGEMENT 54 original typesetting files. Page breaks are true to the original; line lengths, word breaks, heading styles, and other typesetting-specific formatting, however, cannot be About this PDF file: This new digital representation of the original work has been recomposed from XML files created from the original paper book, not from the retained, and some typographic errors may have been accidentally inserted. Please use the print version of this publication as the authoritative version for attribution. Second, our view of the nature of low-level risks has shifted somewhat over the past decade. An initial concern that we face rare but potent carcinogens seems to have given way to the view that carcinogens are fairly commonplace and significantly varied in their potency. Recent studies that reveal widespread exposures to natural carcinogens in food (Ames, 1983a) have troubling implications for a risk-management policy based on elimination of carcinogens (Ames, 1983b; Epstein et al., 1984), and strengthens the argument for adopting a carcinogen-management policy that bases regulatory action on both carcinogenic potency and exposure. One effect of the increasing number of candidate substances for regulation, and of the consequent need to set priorities for regulatory effort, is that case-by- case decision making is seen as too cumbersome. The de minimis approach appears to provide a means for simplifying the regulatory process, by providing an alternative to setting standards for substances considered to pose the lowest risks. Such an alternative is particularly important to an agency that has a statutory mandate to regulate exposure to a substance or class of substances but lacks resources to deal with low-risk, low-priority substances. In addition to these regulatory incentives for using a de minimis rule, industry is likely to support this approach since it defines a threshold for regulatory involvement. The de minimis rule could produce greater predictability in regulation and provide industry with a risk target for avoiding regulation. The de minimis approach may also provide a policy solution to questions that lie beyond the reach of scientific resolution. This would reduce the pressures on regulatory agencies to produce scientific judgments about low- level risks where information is limited or unavailable. A major consideration with the application of a de minimis policy to risk management is whether the risks borne by the public or an occupational group would differ from those borne in the absence of a de minimis policy. Clearly, many small risks that would be formally excluded from regulatory concern under a de minimis approach are unlikely to be regulated under any approach. Exposures to these risks are not the issue, since in such cases the de minimis policy would make no difference. However, a de minimis risk policy could be interpreted as formally legitimizing risks that are now permitted on pragmatic grounds only. Although the risks permitted under a de minimis rule would be quantitatively small by definition, the public reaction to such risks may be influenced more strongly by the qualitative characteristics of the risk (Fischhoff et al., 1978). Many of the agents for which the de minimis approach is being considered pose both uncertain and carcinogenic risks; these characteristics appear to enhance the degree of public concern to risk.
