ABSTRACT
The problem o f equivalence forcefully presents itself to both educational and environmental policymakers because their standards are devised to protect entire populations. O f concern to environmentalists, individuals within a given population may be highly variable in their susceptibility to any particular source o f harm. Some may be genetically predisposed to illness. Others may be specially vulnerable because o f their age, sex, lifestyle, or overall state o f health. Some people may have habits, such as smoking or eating fatty foods, that increase their risk above that of other similarly situated people. To set standards that protect a reasonable cross-sec tion of the population, regulatory agencies have to decide how much o f this variability they will factor into their decisions and in what manner. Criteria for when to presume uniformity and when to allow for variance are usually lacking. A typical choice is to simplify variability by assuming the existence of a standard (but, by the same token, mythical) person: one who consumes a specified number of calories from designated food categories, drinks a constant volume o f water, takes a fixed amount o f exercise, and spends unvarying amounts of time each day at work, at home, or on the road. The concept o f the MEI under the U.S. Clean Air Act is ju st one example, in this case legislatively decreed, o f such a standardized person.
