Your article "When Buying Organic Makes Sense -- and When It Doesn't" (Personal Journal, Jan. 16) was refreshing in its presentation of the quietly held view of many scientists that the touted virtues of organic food are exaggerated or non-existent. But you weren't sufficiently skeptical when you accepted the commonly held belief that organic farmers "eschew pesticides and other chemicals in an effort to protect the environment."

In fact, organic farmers are free to use many chemicals on their crops, including pyrethrin (with the formula C21H28O3) and rotenone (C23H22O6), which is a potent neurotoxin long used to kill fish and recently linked to Parkinson's disease. Organic farmers also commonly spray their crops with Bacillus thuringiensis solutions containing BT larval toxins, and they use sulfur and copper (both long-lasting soil contaminants) as fungicides.

Organic-certification rules only prohibit most, although not all, "synthetic substances and ingredients." The word "chemical" isn't used in the rules because there is no intrinsic physical difference between the categories of synthetic and nonsynthetic substances. They are all chemicals.

Nevertheless, organic advocates operate under the pre-scientific delusion that substances produced by living organisms, such as pyrethrin and rotenone, aren't really chemicals, but just organic "botanical" constituents of nature. Even the poison strychnine can be defined as "organic," although it's too lethal for use by organic farmers. In actuality, no currently approved crop pesticide, whether organic or not, has any detectable effect on the health of consumers. The enormous premium paid to purchase organic foods is based on mythology, not fact.