In 1989, 60 Minutes produced a panicky story alleging the chemical Alar (used to retard the rotting of apples) greatly increased the risk of childhood cancers. Across America, parents poured apple juice down the drain and stores pulled apple products from shelves.

The Washington Post described the event as "one of several food scares that turned out to be baseless." Science editorialized that the incident resulted from a "clearly dubious report...by a special interest group [the Natural Resources Defense Council, NRDC]...without the most simple checks on its reliability...." The EPA noted the claims NRDC made against Alar had been rejected in 1985 by an independent congressional scientific advisory board.

It turns out the PR firm Fenton Communications promoted the report to 60 Minutes. Fenton later boasted, "The campaign was designed so...revenue would flow back to NRDC from the public." And it did, to the tune of hundreds of thousands of dollars.

We're rightly concerned about the potential harm, both to us and the environment, from the products of our technologically advanced society. But people often perceive risks to be far greater than they really are. I have many friends who, in an effort to avoid trace amounts of synthetic chemicals found on "regular" produce, eat only organic. Yet they rock climb, kayak, and ski the backcountry. These activities are far riskier than consuming chemical residues on food.

There is a persistent misconception that human exposure to synthetic chemicals is responsible for soaring cancer rates. This is simply not true. Since 1950, the incidence of age-adjusted deaths for all cancers combined (excluding lung cancer from smoking) has been steady or decreasing. The National Cancer Institute has these statistics on its excellent web site: www.cancer.gov/newscenter/2002reportnation.

Another misconception is that synthetic chemicals are more toxic than natural ones. But the fruits and vegetables we eat have evolved complex defenses against predators, most notably toxic chemicals. As a result our diet is rich in natural toxins. Potatoes, for example, contain fat-soluble neurotoxins detectable in the bloodstream of all potato eaters. High levels of these neurotoxins have been shown to cause birth defects in rodents.

Indeed the proportion of natural chemicals that cause cancer in animal tests is the same as for synthetic chemicals -- roughly half. Americans eat an estimated 1500 mg of natural pesticides per person per day. The FDA found that residues of 200 synthetic chemicals, including those thought to be of greatest importance, average only about 0.1 mg per person per day. In short, we eat 15,000 times as much natural as synthetic carcinogens each day.

Some believe that since we've evolved with these natural toxins, we're able to cope with them. Synthetic chemicals, they say, are unnatural, and hence our systems can't buffer them. This line of thinking has several flaws.

First, various cancer-causing agents (e.g., aflatoxins and fumonisins, molds common to many grains) have been present throughout our evolutionary history and we remain susceptible to their toxic effects. Second, humans have mechanisms (e.g., DNA repair enzymes and the detoxifying properties of the liver) that buffer against exposures to toxins at normal levels. We have evolved general defenses against toxins.

That's because our predecessors were predominately herbivores. They encountered a diverse and ever-changing array of plant toxins. A toxin-specific strategy would be a great evolutionary disadvantage as favored foods became scarce or evolved new chemical defenses.

A misguided focus on minor risks, such as pesticide residues on foods, distracts our attention and resources from real human health hazards. Here's an example.

Synthetic chemicals have lowered the cost of produce, thus making it available to more consumers. Other than quitting smoking, eating more fruits and vegetables is the best way to lower risks of cancer and heart disease.

People with low incomes eat fewer fruits and vegetables and spend a higher percentage of their income on food. If, out of misplaced fear, we reduce the use of synthetic chemicals, produce becomes more expensive. The result will be reduced consumption, likely increasing the incidence of cancer and heart disease, especially among the poor.

It's impossible to anticipate and control every risk. Priorities will be assigned. It's only ethical to devote our limited resources to those hazards most likely to cause the greatest harm.