Engineering and Risk Analysis
`Choosing Our Pleasures And Our Poisons: Risk Assessment For The 1980’s’
`Choosing Our Pleasures And Our Poisons: Risk Assessment For The 1980’s’
by William Lowrance
At the root of many contemporary concerns about technology is the question of risk. Most of the controversies over nuclear power, pesticides, and asbestos (to cite but a few examples) focus on the possibility of harm to humans and the environment, the issue of who might be harmed and how much, the matter of responsibility, and the relative merits of various steps to alleviate the risks. As such controversies have become part of the political scene, techniques for risk assessment have emerged and gained in sophistication. In “Choosing Our Pleasures and Our Poisons: Risk Assessment for the 1980s, ” William W. Lowrance reviews the state of the art of this important new field. Originally prepared in 1980 for the American Association for the Advancement of Science contribution to the federal government’s Five Year Outlook for Science and Technology, Lou Tance’s paper explains the concept of risk and shows how quantitative measures of risk are developed and employed. It stresses the need to be explicit in characterizing risks, suggests means of dealing with uncertainties, and places special emphasis on the need to treat risks comparatively so that minor ones do not displace more significant ones on the policy agenda. William W. Lowrance has been a senior fellow and director of the Life Sciences and Public Policy Program at the Rockefeller University in New York City since 1980. Prior to that he held policy, research, and teaching positions at Stanford University, Harvard, the U.S. State Department, and the National Academy of Sciences. A biochemist by training, he holds a Ph. D. from Rockefeller University and is the author of Modern Science and Human Values (Oxford University Press, 1985).
INTRODUCTION It takes only a few highly charged terms to evoke the risk -assessment milieu of the past decade: DDT, the pill, saccharin, “Tris,” asbestos, nuclear waste, Three Mile Island, smoking, black lung, Clean Air Act, Delaney clause, recombinant DNA, 2,4,5-T, “Research Mining versus EPA,” Teton Dam, DC-10….
This rash of accidents, disruptions and disputes has left the public and its leaders fearful that the world is awfully risky and that, although science can raise warnings, when crucial decisions have to be made, science backs away in uncertainty. Further, there is a feeling that as with medical catalepsy, in which the simultaneous firing of too many nerves draws the body into spasms, the body politic has been drawn into a kind of regulatory catalepsy by too many health scares, too many consumer warnings, too many environmental lawsuits, too many bans, too many reversals. A related complaint is that we are afflicted with excessive government intervention, often of a naive, or trifling or nay saying sort. Among professional analysts as well as members of the public, there is a conviction. that many risk-reduction efforts are disproportionate to the relative social burden of the hazards.
Public apprehensiveness has a number of causes. Is life becoming riskier? Not in any simple sense…. Many classical scourges have been conquered; infants get a healthier start in life; on average people live longer lives than ever before. The historical record of floods, hurricanes, typhoons, tornadoes, earthquakes and other geophysical disasters shows a relatively constant pattern of occurrence over the centuries. I… What we are menaced by now are enormous increases in the physical and temporal scale and complexity of sociotechnical hazards. Of these, the most threatening are risks having low probability and high consequence, such as genetic disaster, nuclear war and global climate change. Too, alarm arises, in an almost paradoxical sense, because science has become so much better at detecting traces of chemicals and rare viruses and at identifying birth defects, diseases and mental stress. Often we know enough to worry but not enough to be able to ameliorate the threat.’ Warnings and accusations are amplified by the public media, often with unseemly haste. Worse, scientific hunches are announced as scientific fact, only to have to be withdrawn later. With all this, it would be surprising if the public’s sensibilities were not battered….
THE EVOLUTION OF MORTAL AFFLICTIONS In his 1803 Essay on Population Thomas Malthus observed of Jenner’s new vaccine- “I have not the slightest doubt that if the introduction of cowpox should extirpate the smallpox, we shall find … increased mortality of some other disease.” This general expectation holds true today if, in addition to disease, we include noninfectious threats. The communicable diseases of smallpox, diphtheria, typhus, cholera, tuberculosis and polio have been conquered. So have scurvy, pellagra and other nutritional deficiency diseases. Infant mortality has dropped dramatically. As the toll from these causes has lessened, mortality has shifted toward degenerative diseases-notably heart disease and cancer-which are attributable either to personal life style or to causative agents in the environment. While the causes of death have changed, the average age of onset of fatal illness has moved higher. Life span has lengthened. Put crudely, we die now of stroke and cancer in part because we live long enough to do so.
Thus at present in the United States the leading cause of death is heart disease, followed by cancer. The rest of mortality is accounted for by other diseases and by accidents, homicide and natural disasters (in that order).2 Within these gross statistics, however, there is great variability by age and socioeconomic status: Motor vehicles and other accidents kill the most children under 14; for black mates between the ages of 15 and 24, homicide is the largest threat; cirrhosis of the liver is the fourth leading cause of death for people between 25 and 64.
In a recent analysis of the prospects for saving lives in this country, James Vaupel developed the ‘concept of “early deaths.” (The definitional problem is fully treated in his report; for short, early death can be taken to refer to death before the age of 65.) Vaupel concluded:
The statistics indicate that the aggregate social losses due to death are largely attributable to early death and that the losses due to early death are immense, that the early dead suffer an egregious inequality in life-chances compared with those who die in old age, and that non-whites, the poor, and males suffer disproportionately from early death. Furthermore, statistics on the leading causes of death and statistics comparing non-whites and whites, males and females, current mortality with mortality earlier in this country, and the United States with Sweden and other countries suggest that early deaths could be significantly decreased.3
Extrapolation of life expectancy data has led to another provocative observation about survival. Some analysts now speculate that the human species is approaching a “natural” life span limit of about 85 years. These analyses have led James Fries to predict that “the number of very old persons will not increase, that the average period of diminished vigor will decrease, that chronic disease will occupy a smaller proportion of the typical life span, and that the need for medical care in later life will decrease.”4
Surely, coming to terms with these trends will lead us as a society to strive less to fend off full-lifetime mortality and to attend more to illness, accidents and quality of life. Among occupational diseases demanding attention, for instance, are the pneumoconioses.- black lung disease, asbestosis and brown lung (textile dust) disease; among the most debilitating, lingering and painful conditions are arthritis, emphysema and allergies; among “life style” diseases, cirrhosis of the liver and the venereal diseases.
IMPROVEMENTS IN ASSESSMENT
Becoming More Comparative
As a society we find ourselves, relative to all previous human confrontation with mortal risk, in the enviable but emotionally unsettling situation of living longer and healthier lives than ever before; of not having to remain ignorant and vaguely apprehensive of hazards but of understanding many of their causes, likelihoods and effects; and of having now accumulated substantial experience in predicting, assessing, reducing, buffering and redressing harm. Blissfulness is prevented by our having too many options. If we still lived only on the margin of survival, we would not have the luxury of worrying about microwaves and hairdryers. If we lacked scientific understanding and the prospect of taking preventative action, we would be more fatalistic about Legionnaires ‘ disease and toxic shock syndrome. If we had not established the hurricane warning network and the national air traffic control system, we would not have to argue about their budgets.
Howard Raiffa made the central analytical point recently in congressional hearings:
We must not pay attention to those voices that say one life is just as precious as 100 lives, or that no amount of money is as important as saving one life. Numbers do count. Such rhetoric leads to emotional, irrational inefficiencies and when life is at stake we should be extremely careful test we fail to save lives that could have easily been saved with the same resources, or lest we force our disadvantaged poor to spend money that they can ill afford in order to gain a measure of safety that they don’t want in comparison to their other more pressing needs.5
To proceed in dealing with risks without making comparisons, both of import of threats and of marginal risk reduction effectiveness (and cost-effectiveness) of public programs, makes little sense. Yet surprisingly little sophisticated comparative work has been done.
In studies meant to be illustrative, Bernard Cohen, Richard Wilson and others have assembled catalogues of common risks.6 Cohen and Lee have calculated effects from different hazards upon life expectancy (for people at specified ages). They found that cigarette smoking reduces U.S. male life expectancy by six years on average. Being 30 percent overweight reduces life expectancy by about four years. Motor vehicle accidents cut off 207 days. And assuming that all U.S. electricity came from nuclear power and that the unoptimistic risk estimates published by the Union of Concerned Scientists are correct, nuclear accidents would claim 2 days from the life of an average citizen…. Although these studies are flawed in numerous ways, their most valuable lesson has been to illustrate how difficult it is to reduce complex social phenomena, such as cigarette smoking and nuclear power generation, to single scalar risk rankings.
Stimulated in part by the early contributions of Chauncey Starr, …. . assessors have attempted to compare technological hazard to natural hazard.7 For example, the so-called Rasmussen Report attempted to compare nuclear reactor accident risks to those of meteorite impacts and other natural hazards in order to provide some intuitive groundings The difficulty is that reliable numbers are hard to compute, and because polls have shown that most people, including scientists, do not have a very accurate intuitive sense of the likelihood and magnitude of natural hazards, such grounding may not be very useful anyway.9
The next logical step has been to “to compare the relative impacts various risk-reduction measures make on longevity. Shan Pou Tsai and colleagues, for example, have examined the question of what gains in life expectancy would result if certain major causes of death were partially eliminated. They calculated that for a newborn child, reduction of cardiovascular disease by 30 percent nationally would add 1.98 years to life expectancy at birth; 30 Percent reduction of malignant cancers would add 0.71 years; and 30 percent reduction of motor vehicle accidents would add 0.21 years. If such 30 percent. causative reduction were to exert effect during the working years of 15 to 60, there would be gains of 1.43 years (cardiovascular), 26 years (cancer), and 0. 14 years (motor vehicle accidents). “Even with a scientific breakthrough in combating these causes of death, ” the authors concluded, “it appears that future gains in life expectancies for the working ages will not be spectacular.
Obviously the outcome of comparisons is heavily dependent on the way the boundaries of comparison are set…. In calculating the risks of coal, do we count deaths from train wrecks, air pollution or release of radioactive radon from the burning fuel? In assessing nuclear power, do we include terrorist abuse or nuclear weapons proliferation? In appraising solar sources, do we include health effects on copper and glass workers? There is no avoiding such analyses. The problem is to learn how to perform them with technical sophistication and to take due account of all relevant social considerations. Overreaching is hard to avoid. The consolation of most such ambitious studies has been that the process of assessment has itself sharpened the social debate and clarified technical-analytic needs.
That the general public is sophisticated enough to understand and endorse the idea of comparative risk assessment has been demonstrated in such situations as Canvey Island in Britain. Within an area of 15 square miles on that island in the Thames near London are oil refineries, petroleum tanks, ammonia and hydrogen fluoride plants and a liquefied natural gas facility. When a few years ago controversy arose as to whether Canvey’s 33,000 people were exposed to unusually high risks, a thorough government inquiry was conducted. Upon deliberation the residents passed a resolution that no further construction be accepted until the overall industrial accident risk on the island had been reduced to the average level for the United Kingdom. But they did not demand that their neighborhood be risk free. 11
That the same toleration for comparative approaches holds in the United States is evident in industrial areas, such as Ohio and New Jersey, where residents are demanding cleanup, but not closing, of industries. Similar moderation led the voters of Maine, an environmentally sensitive state that has had to deal with cold winters but also with proposals of supertanker ports, in their 1980 referendum to vote against measures that would have had the effect of being more restrictive of nuclear power.
If this country is to move toward more “rational” apportionment of risk-reduction and -management efforts, we must assure ourselves that there is reasonable parallel between the burden, in whatever terms, of particular risks and the avidity with which we defend against them, and that programs take into consideration age of onset of harm, degree of debilitation, longevity erosion and cost-effectiveness of ameliorative programs. Before any of this can be done, hazards have to be stated explicitly and goals of hazard reduction agreed upon.
Facing Hazards Explicitly
Comparative approaches are necessarily more quantitative, and they tend to force the revelation of specific consequences. As it dawns on social consciousness that even strict protection inevitably admits some residual harm, even if only by inducing exposure to the hazards of alternatives, little by little public officials have moved toward explicitness.
One of the most widely discussed test cases is that of DES (diethylstilbestrol, the growth hormone sometimes fed to beef cattle). The Food and Drug Administration (FDA) has formally proposed to allow beef producers to use this putatively carcinogenic but economically important agent, if they remove it from feed sufficiently in advance of slaughter that residual DES in marketed beef does not exceed a specified, extremely low concentration. In its proposal the FDA argued that “the acceptable risk level should (1) not significantly increase the human cancer risk and, (2) subject to that constraint, be as high as possible in order to permit the use of carcinogenic animal drugs and food additives as decreed by Congress…. A risk level of 1 in 1 million over a lifetime meets these criteria better than does any other that would differ significantly from it.” The agency noted that further reduction “would not significantly increase human protection from cancer.”12 This proposal and similar ones are predicated on a conviction that the underlying carcinogen assessments are worst possible case overestimates of human risk. The DES standard is still under discussion. In March 1980 FDA Commissioner Jere E. Goyan stated that he would favor amending the food additives laws so that the chemicals testing out under the level of one chance in a million would be permitted (the Delaney clause prohibits even minute traces of very weakly testing carcinogenic additives-a prohibition honored mostly in the breach, because of its absolutist nature).
One by one, as cases have developed-the 1979 Pinto lawsuit, the national review of earthwork dams, amendment of the Clear Air Act-there has been a tendency to require that an upper bound on the estimated actual hazard be stated.
Specifying Risk-Management Goals
Although industrial and legislative programs usually operate under guidelines mandating “reduction of harm” or “protection of consumers,” the degree of reduction or protection is often not specified (except when absolute protection is called for, which, usually being impossible, simply amounts to defaulting). Goal ambiguities may remain even when program objectives are spelled out. Different goals may come into conflict: reducing use of asbestos insulation, in order to protect miners and insulation installers, may have the effect of increasing fire hazard in buildings; forbidding black airmen who are sickle-cell-trait carriers to serve as Air Force Pilots, to avoid the possibility of their becoming functionally impaired under emergency oxygen loss, conflicts with equal opportunity goals.
A recent RAND Corporation study for the Department of Energy (DOE), Issues and Problems in Inferring a Level of Acceptable Risk, lists types of risk-reduction goals that can be considered, such as minimization of maximum accident consequences, minimization of probability of most probable accident and so on. After describing ways in which goal choices can make a difference to programs, the report urges that “DOE and other agencies need to be self-aware in specifying risk-reduction goals, as well as in relating them to goals of other agencies and interested parties, and understanding their implications for the choice of energy alternatives.”13
Skeptics may be tempted to dismiss the topic, saying that we in this country do not have a consensus on social goals. Rebuttal to that too- simple dismissal is evidenced, for example, in the way our medical X ray protection practices, which are the result of decades of reassessment and improvement by industry, medicine and government, pursue goals.- minimization of probability of damage (by decrease in frequency of use of diagnostic X rays, compensated for by more sensitive films), minimization of potentially irreversible damage to the human gene pool (special protection of gonads) and minimization of threat to infants in utero (again, special protection). The typically American goal of helping disadvantaged citizens underlies special health programs for minority groups. The goal of preserving maximum consumer choice can be seen as a goal of food quality programs.
Setting goals is not impossible, but setting realistically attainable goals is not easy. It is imperative that programs be tailored to goals more precise than “protection of all Americans against all harm.”
Weighing Risks in Context with Benefits and Costs