Bill Truesdell wrote: >Just having CL or F in a chemical does not mean it is harmful. Salt, >NaCl is essential for life and most of us brush and usually swallow a >little Fl every morning. HCl is resident in every one of our stomachs. The element chlorine is present in Bill's substances - salt, and aqueous hydrochloric acid in most people's stomach - in the chemical form of the CHLORIDE ion. The giants Davy & Faraday realised this is an extremely different thing from that same element chlorine in other forms. The slightly lesser giant Svante Arrhenius invented the concept 'ion'; at the end of his oral defence of his doctoral thesis at the U of Uppsala, the number of cannon fired at the gate - 1 - was to signal the minimum pass grade, but ions have been beyond doubt for all my life and are always very different from the uncharged forms of the element in question. One of the few good contributions by Barry Commoner was his early essay pointing out that chlorine atoms BONDED TO CARBON are very rare in nature (and when they do occur naturally, they strongly tend have unusually powerful properties, e.g. as bactericides), so it would appear to be a bad idea to spread around vast amounts of organochlorines as has been done since WW2. The same is even more true of the other halogens - the elements in the same group of the periodic table as chlorine. Fluorine bonded to carbon is a very different type of chemical than the fluoride ion as added to some toothpaste, and scarcely occurs in nature. It has unpredictable effects - e.g. the drug fluoxetine as outlined by Bill. My mentioning that by a typo months ago should cause no more trouble, but it is an interesting case of biological effect from an organofluorine compound. The main problem with organochlorine compounds, and organohalogen compounds generally, is that they tend to accumulate in organisms. There are few natural detoxication mechanisms that can handle them, and few enzymes can metabolize organohalogens. They notoriously tend to accumulate, often in fatty tissues. When they trickle back out, e.g. in a famine as fat stores are mobilized, they tend to cause a large variety of biological harm. All this has been in Time-Life books for a couple decades; is in every textbook of applied ecology; yet is ignored by any who try to judge the toxicity of an organic compound by comparing with inorganic ions. (Actually, the fluoride ion is about as toxic as the forms of arsenic that have been used as poisons; and if you drink water with more than a few ppm F- (as do millions of poor people in parts of India & China) you are liable to malformed bones & teeth; fluoride ion is far from harmless.) The total experience with sythetic organochlorine compounds has been worrying. The ecological fate of fluvalinate has not been studied much, and its effects on bees should have been more studied before it was put into commerce. Research on less toxic varroacides should be a far higher priority. Why would anyone disagree with that? R - Robt Mann consultant ecologist P O Box 28878 Remuera, Auckland 1005, New Zealand (9) 524 2949