Risks and Risks

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Science  30 Sep 2005:
Vol. 309, Issue 5744, pp. 2137
DOI: 10.1126/science.1119787

When society makes a decision about some action (to build a dam or approve a new drug, for example), its choice is usually based on a comparison of risks and benefits. If the latter exceed the former, assuming that risks and benefits accrue to the same person or group, the project goes forward. But we do not live in a black-and-white world, and outcomes sometimes don't fall readily into a yes-or-no choice, especially when there are alternative ways of gaining the same benefits. In that case, the only realistic basis for choosing comes down to a comparison of the risks associated with each alternative.

In the United States and some other industrial democracies, where people and their governments tend to be risk-averse, legislatures, courts, and administrative entities usually create a presumption favoring more safety rather than less. The definitions of risk in law are often vague (“reasonable certainty of no harm” or “adequate margin of safety”) and are likely to encourage an unrealistic belief that risks can be minimized or even eliminated altogether. A frequent result is that legal choices for administrative agencies or individual decision-makers amount to all-or-none options, leaving little room for intermediates.


But on occasion, a zone opens for risk comparisons, as in the following examples. Suppose a municipality is treating its water supply with chlorination. Chlorine sometimes combines with organic compounds in natural water supplies to form chlorinated hydrocarbons, some of which have carcinogenic potential. The Environmental Protection Agency (EPA) is charged with regulating such substances, but it is also responsible for controlling waterborne infections. In determining appropriate levels of chlorination, the EPA had to balance the risk of such infections against the risk of contamination with small amounts of a potentially cancer-causing substance. In a lengthy negotiation, the EPA undertook a risk-balancing exercise, resulting in a decision about the safe (least risky) level of chlorine addition.

Or suppose you're taking a prescription drug that relieves a painful arthritic condition. Suddenly a study conducted by a large health maintenance organization shows that at doses higher than those used by patients seeking relief from chronic joint pain, there is a risk of cardiac malfunction—a risk twice as great as that of control subjects. You have to decide whether the risk of continuing to take the medicine is greater or less than the risk associated with your mobility loss and pain. Over-the-counter anti-inflammatory drugs may cause some digestive tract problems, so you prefer not to switch to them. There's no history of heart disease in your family, so you become more comfortable with the drug's cardiac risk. In the end, after consultation with your physician, you decide to continue the drug regime despite the warning label.

There may be a lesson here for much larger-scale societal decisions. For a number of reasons, many developed nations have concluded that the risks of nuclear power generation are too great to engage in traditional risk/benefit assessment of its use. But there is a growing scientific consensus that the emission of carbon dioxide and other greenhouse gases, released in the course of energy production and industrial combustion, is related to global warming. It is clear that business as usual will entail increasing climate-associated risks. Nuclear power is an alternative that emits no greenhouse gases. On the other hand, it presents risks that include nuclear accident, diversion and proliferation of fissile material, and uncertainty about the management of high-level waste.

These are substantial risks, all right. But so are those associated with global climate change: rising sea levels, increased frequency of extreme weather events, changes in agricultural productivity, and weather-induced hazards to human health. Balancing these kinds of risks will require complex and difficult decisions, and the need to make them will be a challenge to our societal appetite for no-risk solutions. Just as we compare risks as we seek to protect or improve our personal health, we will need to do so on a larger scale as we seek to manage the environmental effects of our industrial economy. In the latter case, it is pointless to take one option off the table without a serious comparison of risks. We may wish for safe solutions, but neither option is free of risk, leaving us to make choices among imperfect alternatives. The real world is complex, but it's the one we have.

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