Myths about the risks of various products and activities can themselves be harmful to your health. They include the belief that greater regulation is synonymous with greater safety, and that excess or unnecessary regulation is harmless. Self-promoting, self-styled "consumer activists" perpetuate and feed off those misconceptions.
For example, the Natural Resources Defense Council  last month filed a lawsuit against the Food and Drug Administration  because of the agency's refusal to ban bisphenol-A (BPA), a chemical found in many consumer products. The regulators' rationale was clear: There is no evidence that the chemical causes harm to human health.
But activists remain unpersuaded - and they fail to grasp that banning or restricting BPA could itself cause significant harm.
For more than 50 years, BPA has been an important additive that helps make the plastics used in everything from soda bottles and plastic storage containers to medical devices and children's toys tough yet flexible. It is also used in the lining of food cans to prevent spoilage that can lead to bacterial contamination and the risk of botulism.
BPA is one of the most thoroughly tested chemicals of all time. And regulatory authorities from around the world, including the FDA , have judged BPA to be safe at the very low levels at which it is used, and to which consumers are exposed.
Nevertheless, some environmental activists have long sought a ban on the substance because at very high doses, BPA acts like the hormone estrogen and might theoretically lead to brain, breast or prostate abnormalities. However, a basic tenet of toxicology is that the dose makes the poison. This means that mere exposure to a chemical like BPA does not imply harm; one needs to know the dose and length of exposure, what the substance does (if anything) in the body, how it is disposed of and so forth. Virtually any substance can be toxic at high enough levels.
Regulatory decisions rely on risk-benefit assessments. There is no doubt that using BPA makes many of the products we use safer, more effective and longer lasting, but activists choose to ignore the health-enhancing benefits that BPA delivers and focus exclusively on potential (and unproven) harm. And in that respect, BPA is far from unique. Even when repeated testing shows such products to be safe at or above normal exposure levels, activists insist that regulation be based on the so-called "precautionary principle," a belief that governments should implement regulatory measures to prevent or restrict actions that raise even conjectural threats of harm to human health or the environment.
This risk-averse approach is sometimes represented as "erring on the side of safety." As it is typically applied, however, the chaotically worsening outcomes are coming from regulators who fail to take into consideration not only credible, but inevitable, worst case harms that would result from forgoing important products and technologies. This tunnel vision application of the precautionary principle actually makes us less safe.
Nevertheless, radical environmental groups have prevailed upon governments in recent decades to burden various industries with precautionary regulation. It has already laid to waste several industries and distracts consumers and policymakers from known, significant threats to human health and the natural environment, diverting limited public health resources from those genuine and far greater risks. Absent our current highly precautionary approach to nuclear power, for example, we could reduce coal and oil exploration and their attendant damage to human health and the environment.
An egregious application of the precautionary principle is the environmental movement's misguided crusade against so-called "endocrine disrupters" which is based on the premise that certain primarily man-made chemicals mimic or interfere with human hormones (especially estrogens) in the body and thereby cause a range of abnormalities and diseases related to the endocrine system.
Although very high doses of certain environmental contaminants produce harmful effects in laboratory test animals - in some cases involving the endocrine system - humans' actual exposure to these suspected endocrine disrupters is many orders of magnitude lower than the lowest level known to cause any harm. Although they are among the most widely studied substances in history, no consistent, convincing association has been demonstrated between real-world exposures to synthetic chemicals in the environment and increased cancer in hormonally-sensitive human tissues.
Moreover, most human exposure to estrogen-like chemicals is through food. A single one-ounce portion of tofu, for example, contains more than 9,000 times as much of these natural estrogen-like substances as a typical human baby gets from drinking milk out of a polycarbonate bottle - and babies are generally thought to have higher exposures to BPA than adults or other children.
There is no scientific reason to believe that typical exposures to these estrogen-like substances, whether natural or synthetic, pose any danger at all to human health. But the use of endocrine-mimicking chemicals like BPA helps to protect us from myriad risks ranging from food-borne illness to cuts and other injuries that would surely increase if the government were to ban BPA.
History offers compelling reasons to be cautious about technological risks, to be sure. But the challenge for regulators is to balance competing risk scenarios in a way that reduces overall harm to public health and the environment. Caution misapplied can make our lives more dangerous.