The health-scare headline of the week: “Americans found to have twice as much bisphenol A in their bodies as Canadians.”

BPA, as it is known, is a widely used chemical found in baby bottles, containers, CDs, car dashboards, and even dental sealants. A new survey finds that Canadians on average have about 1 part per billion of BPA in their urine, while Americans have twice that amount.

“That’s bad news for Americans,” observes Mother Nature Network News. “Scientists are worried about BPA,” writes the Toronto Globe and Mail.

But most scientists are not worried and do not see this survey as bad news. In fact, it’s not news at all. The hundreds of media outlets that ran with this story failed to mention that regulatory scientists throughout the world have uniformly concluded that these levels of BPA are so miniscule as to be basically harmless. “Finding a measurable amount of bisphenol A in the urine does not mean that [it] causes an adverse health effect,” the Centers for Disease Control and Prevention reported recently, noting that it is found in more than 90 percent of Americans but is “excreted in the urine within 24 hours with no evidence of accumulation.”

When it comes to stories on so-called toxic substances, the public discourse seems infected by a malady worse than microscopic residues: chemophobia. Webster’s defines chemophobia as the irrational belief that “chemicals” are bad and “natural” things are good.

In fact, labeling a chemical “toxic” or a “contaminant” is meaningless. Toxicity is a question of degree; exposure is different from effect. Apples, bananas, basil, broccoli, cabbage, citrus fruits, mushrooms, turnips, and many more foods contain naturally occurring chemicals that are toxic — they cause cancer at large lifelong doses in laboratory rodents. Tofu is more estrogenic than BPA.

The chemophobic narrative derives from the precautionary principle — the notion, popular in Europe, that a substance can be banned if it is potentially harmful, even absent hard data demonstrating a cause-and-effect relationship. This is not a scientific standard. In its most extreme applications, tradeoffs are not considered, such as the harm that might be caused from restricting a particular technology or the potential danger of substituting an untested substance for a thoroughly evaluated one.

More than anything, this principle gives legislators and politically appointed regulators — some with limited scientific knowledge — the freedom to pick and choose which substances to restrict. And it threatens to replace the risk standard long used in the U.S. and in most of the world.

Risk describes the probability of danger. The key is setting an appropriate threshold. Until now, regulators have been ultra-cautious, especially in America — establishing limits hundreds to thousands of times more restrictive than those suggested by studies on sensitive laboratory animals. But today, scientists can identify a thimble-full of a chemical after it’s poured into Lake Erie. Playing on unscientific fears of trace levels of chemicals, activists are putting pressure on regulators to set thresholds even lower — without evidence that current standards are inadequate.

Consider the case of California almonds. A natural chemical, aflatoxin, is found in 15 percent of this crop and on other nuts as well. If the aflatoxin is not eliminated before the nuts are consumed, people could die; and the most effective way to eliminate aflatoxin in nuts is with pesticides — triazines, such as simazine and atrazine, which have been found safe at levels up to 1,000 times what humans are exposed to when they’re used on nuts. But many environmental campaigners, citing controversial studies on frogs, lobby for a ban of triazines.

Agricultural chemicals are among the most scrutinized and regulated of all technologies. In Europe, whose regulations are already more restrictive than those in the U.S., governments are phasing in precautionary criteria that could blacklist 22 chemicals– about 15 percent of the EU pesticide market. Some environmentalists are pressuring U.S. regulators to abandon a risk-based approach for this more politicized European standard. That would be a mistake. The bottom line is that in order to maintain healthy crops, farmers fight a constant battle against insects, fungi, and plant diseases, as well as weeds (which compete with crops for water, nutrients, and light). Advanced chemical technologies have helped to prevent infectious diseases and to enhance crop yields. These are the drivers of the Green Revolution, which has dramatically cut world hunger over the past 60 years.