It is ironic that cost-benefit analysis, under a variety of names, is so casually accepted in the "non-scientific" fields of politics, industry, and business, but is a source of major controversy and debate among many scientists, even though they, by tradition, have preempted the field of quantitative evaluation of phenomena and interactions. I believe the problem arises from the "subjective" variables which much be included in cost-benefit analysis even though they are difficult or impossible to quantity. Yet, in many cases, if the variables to be considered are limited to those that can be accurately evaluated, the scope of the analysis will be much too limited; costs, risks and benefits can be evaluated to any desired accuracy, according to any internally consistent method, and still be irrelevant to the problems of the day. For examples the risks of carcinogenesis from both nuclear and fossil-fueled power plants should be compared. Neither of these risks is intrinsically very high, but the degree of public concern surrounding the issues is so great, the evaluation problem itself is of exquisite importance. For this reason, an "objective" cost-benefit analysis would be virtually useless if it did not address the real, but subjective, problem areas.
Before proceeding, I would like to make a distinction between "costs" and "risks" to provide a frame of reference for comparing them. Costs are effects which vary continuouslywith their driving forces—in relation to society or the individual. On the other hand, discrete phenomena, which are either manifested or not in individuals, have associated levels of risk; the value of the risk is defined as the probability of the phenomenon's occurrence.
Risks can be characterized as costs if the frame of reference is expanded from the individual to the society as a whole. In other words, the occurrence of discrete events can be approximated by a continuous function if the population is large. As an example of the "cost-valuation" society applies to such phenomena, cancer is considered to be worthy of a much greater research investment than anyotrophic lateral sclerosis, an invariably fatal—but much rarer—disease. Accordingly, there is ample precedent for considering costs and risks to be qualitatively equivalent if the frame of reference is larger than the individual. With this justification, a major task confronting cost-benefit analysts and decision-makers is to find an acceptable medium of exchange, or common basis for quantitative comparison, for the two.
In medicine, a recommendation for treatment is made if it is predicted that benefits will be derived which outweigh the risks and costs. The benefit the patient can expect is the overall reduction of the risk of mortality or morbidity, but this benefit will really exist only if the diagnosis is correct; it is inevitable that for some cases, the costs and risks of the treatment will be incurred with no actual benefit at all. The art of medicine is practiced acceptably, though despite a significant degree of uncertainty surrounding specific applications to individuals. The acceptability results from the favorable integrated benefit-cost balance it offers the society as a whole, and also from the generally recognized fact that research designed to improve this balance is continuously in progress.
In the field of cost-benefit analysis, as in the field of medicine, there are strong pressures to produce acceptable solutions for current problems. Decision-makers cannot always wait until they have all the facts. Consequently, human judgment and intuition must be used to extend the relevance and applicability of limited information and meager knowledge. Since society both provides the pressures for solutions, and establishes the levels of acceptability, this intuitive approach will be most productive if the scientific and technological institutions work together with our broad social and political bodies. Furthermore, these institutions must use trial-and-error problem-solving methods, so they cannot realistically be expected to uniformly provide perfect solutions.
A prospective risk-acceptability evaluation is much more difficult, obviously. This approach must be used, though, to estimate the extrinsic value that is placed on a future risk, such as that from nuclear power plants. I anticipate that society's reactions to new, and therefore untested, risks are likely to be manifested by high extrinsic values on the risks. Again, psychological characteristics of individuals are expected to determine the population response; in this case, intrinsically low-level risks that are unfamiliar are likely to be given higher extrinsic valuation than equally low level risks that are familiar. Thus, "fear of the unknown" and " familiarity breeds contempt" are reactions that must be expected.
It is hoped that benefit-risk analysis can be helpful in reconciling the differences between intrinsic and extrinsic evaluations. Reaching this goal itself, however, is an independent problem. To accomplish it, the level of familiarity for the projected risk might be increased by an abstract education process. Since intuition, a process of mental analogy-referencing, is a necessary part of risk evaluation, the public might be effectively informed by referring to risks in already familiar terms. Perhaps, for this purpose, a unit of risk might be used that has a name such as "cig," which would be defined as the level of risk incurred by smoking a single cigarette.
Except for thermal release, which is about the same quantitatively for fossil-fueled and nuclear plants, the potential environmental effects of operation of these sources are not directly comparable. Most of the harmful effects of fossil fuel combustion are manifested as costs—acute human health effects, and damage to materials, plants and commercial crops. On the other hand, the expected radiation-related effects of nuclear plants are risks—these would result from long-term low-dose exposure to radionuclides. Still, there is a body of experimental evidence suggesting that combinations of air pollutants emitted from fossil fuel combustion processes, including electrical power production, are capable of producing and/or promoting cancer.2
It can be predicted that fossil-fuel pollution presents a significant risk of carcinogenesis to the general population. This qualitative prediction is based on two sets of observations; first, that benz(a)pyrene (BaP) is one of the most potent and most abundant of the carcinogens in cigarette smoke, and second, that the ambient air of American cities contains enough BaP to provide a dose rate to individuals equivalent to that of light smokers. It is not accurately known whether the magnitude of the risk is of the same order as that from radiation-related environmental pollution due to nuclear power production. Nevertheless, the qualitative prediction carries with it a presumption that must not be ignored when comparing the relative environmental costs of nuclear and fossil-fuel power production.
A very rough approximation of the dose-risk relation for BaP alone can be made by referring to the smoking-cancer studies, by oversimplifying in places and by ignoring co-carcinogens altogether. This value, in turn, can be used to estimate the magnitude of the risk incurred by breathing polluted air. These calculations depend on a few simplifying assumptions: (1) the lung cancer initiation rate among cigarette smokers increases linearly with the integrated BaP inhalation rate; (2) the co-carcinogens in cigarette smoke amplify the effectiveness of BaP by a factor of 40; that is, BaP alone accounts for only 1/40 the total activity of cigarette smoke; (3) the effective duration of risk in the human population is 40 years; and (4) by averaging the male and female lung cancer initiation rates for the range of 1-19 cigarettes a day, a wide range of physical smoking parameters will be included.
A "bapman" is defined as a unit of exposure of one man to one microgram of BaP in one year. The annual rate of BaP exposure from smoking 10 cigarettes a day is about 60 micrograms. Using the assumptions above, and values of the annual excess risk of lung cancer for all ages of smokers, men and women taken together,3 it can be shown that the risk associated with one bapman exposure is 5 x 10-6. In other words, 2 x 105 bapman of exposure would result in one death. It follows that the risk associated with the bapman unit is about an order of magnitude less than that for a man-rem.
The exposure to BaP from ambient air breathed by American urban populations can be calculated in bapman units by referring to data in the literature,4 and by assuming a daily tidal volume of 30 cubic meters. For 10 cities, representing a total population of 17.2 million people, the exposures range from 2.6 x 107 bapman in New Orleans, to 4.9 x 108 bapman in New York. The calculated average projected death rate using the 10 city sample is about the same as for light smokers—48/l00,000 population—on an annual basis. For a population of 100 million persons at risk, the predicted incidence of cancer resulting from BaP exposure is 48,000. Assuming that electrical power generation accounts for only 1% of the total BaP in the atmosphere, the expected number of deaths due to fossil fuel power production is about 480/year currently, from an exposure of 3 x 106, bapman. By comparison, this risk is larger by a couple of orders of magnitude than that expected to result from the 5 to 6 x 104 man-rem due to nuclear power production by the year 2000.
Risk-acceptability evaluation is distinguished from risk evaluation, and is considered to be relevant to the overall goals of cost-benefit analysis. It is suggested that the public might over-react to proposed projects, despite small intrinsic risks, because there is no intuitive familiarity for phenomena which have not been experienced. It is proposed that the disparity between intrinsic and extrinsic risk values can be reconciled by positive attempts to inform the public, with the goal of increasing the public's familiarity with risks.
As an example of the use of comparative risk evaluation, the risks of carcinogenesis from fossilfueled and nuclear power generatrion are compared. Despite considerable uncertainty in establishing the magnitude of the risks, it is shown that current levels of pollution from fossil-fueled power plants constitutes a risk that is probably considerably higher than that from projected nuclear power plants.
2. Watson, D. E., The Risk of Carcinogenesis from Long-term Low-dose Exposure to Pollution Emitted by Fossil-fueled Power Plants, University of California Lawrence Livermore Laboratory Report UCRL-50937, October 1, 1970. (Reprints available.)
3. Hammond, E. C., "Smoking in Relation to the Death Rates of One Million Men and Women," in Epidemiological Approaches to the Study of Cancer and Other Chronic Diseases, National Cancer Institute Monograph 19, January 1966.
4. Preliminary Air Pollution Survey of Organic Carcinogens, National Air Pollution Control Administration Publication No. APTD 69-43, U.S. Dept. of Health, Education and Welfare, P.H.S., 1969.