HAZARD DEFINITION AND ASSUMPTIONS
Societies differ strikingly in their approach to answering the questions of whether hazards exist. Differences in regulatory philosophy profoundly affect the exposure regulations that result from hazard assessment. The hearings discuss at some length the differences in the Soviet and the American philosophies of setting standards for exposure to electromagnetic fields. The following discussion highlights some of the overall differences defining hazards-an undertaking that the SRI project team considers to be a social process, which uses the information gathered by the scientific community on biological effects as one of its many inputs.
The term "hazard" used in this text should be considered a legal or regulatory term that implies a judicial or quasi judicial determination that the biological effects of substances or forces introduced into the human environment are undesirable or unacceptable. Determining biological effects is a scientific and technical problem. Interpreting information on effects to arrive at a hazard evaluation involves assumptions and philosophical problems that lie outside the scope of science and, frequently, outside the scope of law: Which biologic
effects should be considered? What criteria should be used in categorizing an effect as unacceptable? Is there an intensity or concentration threshold for an effect? What consideration should be given to the rare individual who is exceptionally sensitive? And who should bear the burden of proof in determining that an effect or hazard exists?
Many of these questions were encountered in the development of air quality standards for industries and factories in the United States and the USSR between 1946 and 1970. In the United States, the American Conference of Governmental Industrial Hygienists developed the concept of the Threshold Limit Value (TLV), defined as the time-weighted average concentration of an airborne substance to which most workers could be exposed 8 hours a day, 5 days a week, for an indefinite period without adverse effect. In the USSR, the State Committee on Standards of the Council of Ministers developed the concept of Maximum Allowable Concentration (MAC), defined as that concentration of an airborne substance that will not produce in any of the persons exposed any disease or any deviation from normal. The assumptions underlying both viewpoints are clear: In the United States, harmful effects are emphasized, whereas in the USSR any effect out of the ordinary is considered undesirable. In the United States, the hypersensitive individual is excluded, whereas in the USSR all individuals are included. In both countries a threshold is recognized, below which no effects are induced.1
The concept of threshold was central to the formulation of protection standards in both the United States and the USSR. This concept applies in principle not only to industrial air quality standards but also to safety standards for food additives and colorings, and to other conditions considered to have health significance (e.g., exposure to electric fields in the USSR). In recent years the concept of threshold as a defining limit of permissible exposure has been questioned in the United States with (1) the development of increasingly sensitive methods for determining biological effects; (2) disagreement about what constitutes a "harmless" effect, including concern about the additive effects on an individual of several environmental factors; and (3) public concern about the possibility that certain environmental pollutants may be carcinogenic or increase susceptibility to cancer. To meet these concerns, the concept of risk (or cost) benefit analysis has been developed. Carried to an extreme, risk/benefit analysis ignores the question of threshold, and attempts to establish a limit of permissible exposure by compromising among the social and personal advantages or detriments associated with an environmental pollutant or physical force.
Risk/benefit analysis is frequently used by government agencies to assist in decision making. For example, a current controversy in the U.S. Food and Drug Administration (FDA) concerns the question of whether or not the use of nitrites in the preparation of bacon, ham, and sausages should be permitted. Opposition to nitrites is based on the possibility that they may react with organic materials in food to produce nitrosamines, which are considered to be strong carcinogens. However, the FDA continues to permit nitrites because they inhibit the growth of the bacteria that cause botulism. The benefit in preventing botulism is considered to outweigh the still questionable (unquantified) hazard of cancer.
The chief disadvantages of risk/benefit analysis are that risk and benefit are more difficult to define and measure than threshold or injury and that definitions are contingent on personal viewpoints. In the example cited above, the risk and benefit occur in the same person, and that person can recognize this fact. In the hearings under review, the ordinary person living along the power line right-of-way probably perceives the risk as personal and the benefit as accruing to a remote and indifferent corporation. Benefit to "society" may well be perceived in the same way. Hence, risk/benefit analyses must consider the distribution of risks and benefits and how these factors are perceived by the persons affected.
Two assumptions occasionally exist-sometimes tacitly-in positions on environmental pollution. One assumption is that a substance or agent must be assumed harmful until proved otherwise ("guilty until proved innocent"). For at least 20 years the FDA has used this assumption as the basic guidelines for licensing food additives and colorings and new drugs. The extension of the assumption to everything in the environment is relatively recent, and advocates often do not consider the economic consequences.
A second approach that frequently underlies attitudes about environmental pollution is the black/white assumption: A substance or agent is or is not harmful or dangerous to human health. If it is harmful, it must be removed or at least reduced to the lowest possible level. With respect to some naturally occurring substances and phenomena, such an unrestricted assumption is scientifically unsound. A number of naturally occurring substances, including the oxygen in the atmosphere that we breathe, are essential or beneficial to life at one concentration and toxic or detrimental to life at higher concentrations. The key point is the dependence of the effect on concentration or intensity. Some substances or agents such as carcinogens may, in fact, be deleterious to some degree at any concentration ("zero threshold"), but failure to consider concentration or intensity (dose) dependence could lead to unrealistically low environmental concentration standards, with the attendant cost borne by the public.
1 It should be noted, however, that every substance or force in the environment probably has biological effects at some concentration or intensity. Even the noble gases - helium, neon, argon, krypton, and xenon - have well-documented biological effects, although these effects are found at high partial pressures. It is not known whether these gases or other physical phenomena in nature, such as the natual magnetic and electric fields of the earth, have biological effects at the ordinary concentrations or intensities at which they are found; nevertheless, such a possibility cannot be excluded. Hence, it is meaningless to speak of the absence of effects of a particular substance or agent: the biological effects are either too subtle to be detected or cannot be produced at the concentrations or intensities of exposure characteristic of the natural envirnoment. This concentration or intensity dependence is the basis of the concept of threshold.
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