Unit10-2

Health Risks

Opinion polls repeatedly tell us that the only thing Americans worry about more than the environment is their health. This is entirely understandable, for health is obviously preferable to illness. What makes today's preoccupation with health slightly surprising is that Americans are far healthier now than they have ever been. Many diseases that once struck terror into hearts have either been completely eliminated or brought under control. Although AIDS is a notable exception, few new mass killers[1] have come along to replace the ones that have been eliminated.
Nonetheless, health—and the various threats to it—remains everyone's permanent concern. After all, more than half of us (57 percent) will die from either heart disease or cancer, if current trends continue.
One major problem with any comparison of health risks—especially life-threatening ones—is that they differ enormously in their immediacy. For instance, AIDS—if you get it—will probably be fatal after a number of years. Cancer induced by smoking or exposure to radiation, on the other hand, may take 20 to 30 years before its catastrophic effects show up. In making choices about health risks, therefore, it is important to bear in mind the likely time lag between taking a risk and suffering its consequences.[2]
Those with a mind to "live for today"[3] are apt to be indifferent to health risks that have a very long incubation period. Although this is short-sighted, it does make sense to discount long-term risks more than short-term ones. After all, when virtually any of us is confronted with the choice of doing something likely to kill us today versus doing something likely to kill us in two decades, the choice is going to be the lesser of the two evils[4].
One commonly used measure to deal with such problems is a concept called years of potential life lost YPLLS. The idea is that for a 25-year-old, doing something that will kill him in 5 years is much more "costly" than doing something that will kill him in 40 years. Both may involve the same element of risk—the same probability of eventually dying from that activity—but a risk that may cause immediate damage is much more costly than one for which the piper needn't be paid for a long time[5]. In the first case, he will have his normal life span cut short by about 45 years; in the latter case, the deficit is about 5 years[6]. Thinking about matters in this light inevitably causes a reassessment of many of the threats to health. For instance, heart disease is the single largest killer of Americans, way[7] in front of cancer or strokes. However, heart disease tends to strike[8] the elderly in much greater proportions than younger people. Cancer, by contrast, kills fewer people but tends to strike somewhat earlier than heart disease. Hence, more(YPLL)are lost to cancer than to heart disease—despite the greater incidence of fatal heart cases. Specifically, cancers claim[9] about 25 percent more (YPLL)than heart disease (if we define the YPLL as a year of life lost before age 65).
The concept of YPLLs has an important, if controversial, influence on issues in health care economics. It is frequently argued that money devoted to medical research on curing diseases should be divided up on the basis of the number of lives lost to each disease. Thus, some critics of the massive levels of funding devoted to AIDS research claim that—compared to killers such as heart disease and cancer—AIDS receives a disproportionately high support. That criticism fails to consider the fact that AIDS, by virtue of striking people principally in their 20s and 30s, generates far more YPLLs than the bare figure of 20,000 deaths per year, bad as that is, might suggest.[10] Put differently, finding a cure for AIDS would be likely to add about 25 to 30 years to the life of each potential victim. Finding a cure for heart disease, although it might save far more lives, would probably add only another 5 to 10 years to the life of its average victim.
The assessment of the seriousness of a risk changes, depending upon whether we ask how many lives it claims or how many YPLLs it involves. Some of the differences are quite striking. For instance, accidental deaths appear relatively insignificant compared to cancer and heart disease when we just count the deaths caused. But once we look at the number of lost years, accidents loom into first place among the killers of Americans. These data show that we need to ask not only how large a risk is but also when it becomes payable. Other things being equal, the sooner a risk causes damage or death, the more that risk is to be avoided.

Risks from Nature and Technology

We live in an age when natural has come to mean "benign"and anything made by humans seems both artificial and suspect[1]. But actually the natural and the benign are not necessarily the same thing. Nature does a lot of nasty things to us. Floods, storms, earthquakes, hurricanes, volcanoes, and tornadoes are just the tip of the iceberg. [2] Most diseases are natural. Many naturally occurring substances are poisonous. The single largest source of cancer-producing radiation is radon gas, a byproduct of the decay of radioactive elements in the earth's crust. Other sources of cancer-causing　radiation are cosmic rays and ordinary sunlight. Indeed,　death itself is natural. If we have been　able to prolong life beyond its traditional span of seventy years, that is because we have been clever enough to contrive ways of delaying the decay, disease, and destruction that is inflicted on us by nature.
Think about it another way. All plants, including those we eat, contain many naturally occurring pesticides. They have evolved these toxic—in many cases, carcinogenic—defenses against insects and other predators over millions of years. It has been estimated that we consume 10,000 times as many natural pesticides as artificial ones. In other words, nature is not benign. Other numbers prove this even more convincingly. It is a widely used rule of thumb[3] among risk specialists that, in any given year, about 30 times as many people will die in natural disasters as in man-made ones.
In addition to natural catastrophes, there are still plenty of ways in which our technological society poses[4] major threats to our lives and health, especially through damage to the environment in which we live. The unhappy fact is that we have some grounds[5] for thinking that many air and water pollutants may be risky, but we have as yet no dependable data on the size of the risk they pose. In other words, although we have a pretty good idea of the amount of the principal pollutants released into the air and water in the United States, there are very few studies on the health effects of specific concentrations of particular pollutants. Such studies are difficult to perform because there are too many variables outside our control. Is a certain oxide of nitrogen dangerous in a particular amount? Usually the answer is that we do not know.
Because everything is risky, it is meaningless to be told that this or that pollutant　poses a "potential" risk—until we know what the risk level is. Unless we know whether a certain pollutant in certain concentrations kills 5,000 people a year or 1 person every decade, we cannot decide whether it poses an unacceptable risk. Scientists have generally not yet been able to identify the size of many of the risks posed by most of the pollutants in the environment.
In fact, such studies as there are raise doubts about the commonly assumed risks of some pollutants. In New York City, for instance, levels of sulfur dioxide fell more than 90 percent between 1969 and 1976 in response to the Clean Air Act of 1970. Despite this major shift in one of the most common air pollutants, daily mortality rates in New York did not change at all. No doubt New York City smells better, but it is unclear whether any lives were saved by the reduction in sulfur emissions.
The problem of assessing environmental risks is made worse by the official doublespeak　on the subject. Consider but one example. From time to time, a federal agency　will announce that it has identified a certain substance (natural or artificial) as a "possible human carcinogen". Such announcements are generally greeted with much wringing of hands from the general public, who suppose that one more item must be taken off their menus.[6] The facts, however, are quite otherwise. To qualify as a possible human carcinogen, there must be evidence that the substance in question produces cancer in rats when they receive doses of the substance that are often a million times stronger than a human being receives, even allowing for differences in body weight.[7] Even if we suppose that the likelihood of cancer varies directly with the level of exposure and that whatever is carcinogenic to rats is dangerous to humans (and both assumptions are dubious), these figures mean that the likelihood of a human　being getting cancer from normal exposures to the substance is about a million times smaller than the rat's chances.[8] If you reflect on the other risk statistics, it will become clear that such a risk is extraordinarily low—in fact, it is about as close to "safe" as we normally get in this life. Accordingly, the discovery that something is a possible human carcinogen is the discovery that it may be less harmful than many of the things we routinely do.[9]