The dreaded mad cow disease has finally arrived. How worried should we be? Do I need to avoid the range cattle I come across on my hikes in Montana or skip that steak when I visit Bozeman?

This issue is complicated by scientific complexity and strong emotions -- ingredients for error. Given their limited resources, how can policy makers most effectively protect public and environmental health?

The situation invites “risk analysis.” This process comprehensively and quantitatively considers the nature of the hazard, exposure, severity (death or something less from that exposure), and epidemiology and toxicology.

The U.S. Department of Agriculture asked our Center in 1998 to analyze the risk of mad cow disease in the U.S. For three years we studied everything from the natural history of this strange disease to on-the-farm practices to slaughtering and rendering. This work enabled us to construct a computer model simulating if (now when) mad cow disease was introduced to American cattle.

The good news in terms of health risk to other animals and to humans is simple -- little happens. Our analysis found that even if compliance is imperfect, government’s ban on feeding cattle protein back to healthy cows chokes off the disease. Additional measures, which the USDA implemented after a mad cow was discovered in Washington, reduce the low risk even further.

Risk analysis also often weighs the benefits and costs of various risk-reduction/health-improving strategies. For each, we consider the number of lives saved, diseases prevented, quality of life protected -- and the cost of each strategy. The goal is to identify how our society’s limited resources can do the most good.

Some object to such antiseptic analysis. They find placing a dollar value on human risk morally unacceptable. Explicitly quantifying risks to life and assigning dollar values may seem harsh. However, we commonly allocate funds to our own health and safety. Consider smoke detectors and new tires, expensive health insurance or whole-body MRI exams. If we can’t have it all, we intuitively balance the benefits and costs of alternatives. For policy makers, risk analysis makes such decision making more honest and explicit.

Debates about risk issues are often emotionally heated and charged with competing values. Risk analysis applies a cooler, science-based perspective. The resultant insights favor no ideology, no political or corporate agenda. It’s entirely reasonable to use the neutral tools of decision science and risk analysis to sort among various health threats. The goal is to identify choices that will benefit the most people at the least cost.

However, as Paul Slovic and others have found, personal perception of risk is an emotional, intuitive, instinctive process. We fear risks that kill us in dreadful ways, shark attacks for example, more than deaths that seem relatively benign, like heart attacks. Risks to kids (abductions), risks that are new (SARS), risks that are fraught with uncertainty (the Washington, DC sniper), risks over which we have no control (flying), all demonstrate that the emotional aspects of a risk matter as much as the odds.

Certainly policy makers in a democracy must consider these emotions. The USDA has done just that with mad cow disease, recalling meat that is not considered a risk and imposing a series of increased controls. This will further reduce an already small risk and help reduce fear.

But money, time, and attention applied to “fear button” risks divert resources from greater risks. As a result, some exposed to greater risks will get sick, or die. Mad cow disease displaced flu from front pages. Yet flu will cause 20,000 to 30,000 or more deaths in the U.S. this year. To promote public health, policy makers must identify these larger risks and cost-effective responses. Risk analysis fosters clarity when considering such problems.

Our ancestors lived in a world where many (perhaps most) threats were obvious. But we lack the luxury of that simplicity. Our modern world, with all its benefits, comes with a bewildering web of potential threats. Our instinctive responses are often wrong. Thinking logically about our perils, and carefully analyzing our choices for dealing with them, is an important way to identify the preferable solutions. Risk analysis helps us maximize public and environmental health and safety.