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Originally Posted by macgardener
Hmm, less toxic than common salt. Where have I seen that sort of comparison before? Oh yes, on the documents we were given by a pest control company when we requested MSDS's. Not having seen an MSDS before we didn't realise until later that the single page of reassuring advertising was not in fact the information we had asked for. I've had a rather negative view of the salt comparison ever since. Actually I haven't often come across it since, though I suppose it could be seen as a way of explaining something scientific in terms that your average fast-food consuming ignoramus might understand.
I'm afraid that LD50's of active ingredients don't address all my concerns about pesticide use anyway. Solvents? Synergists? I know a couple of mothers whose children have reacted (in different ways) to exposure to pesticides (in one case at least it was more likely the solvent). I have sensitivities myself. On this occasion no apparent immediate harm was done but I can't always be sure what will happen. I wonder what is the LD50 of a surface cleaner popular with shop assistants. Inadvertently going within a few metres when someone sprays leaves me with stinging eyes for some time afterwards. I was pleased to see in a local dress shop recently that the shop assistant was cleaning the mirrors with a refillable bottle of water. I asked her about it and she said it was in response to complaints by others like myself who are bothered by chemical cleaners. Another plus in not using a chemical is not having the packaging to dispose of afterwards. And that's applicable to pesticides too.
I wish I could persuade more people to have a garden like mine, where the strongest things I use are a bit of muscle, and seaweed solution, but some people prefer to use those easy quick fixes which they are led to believe are safe. I don't particularly wish to debate the safety of any specific product, I always feel that lurking amongst the current "safe" products is the next DDT, asbestos, thalidomide, diethylstilboestrol, etc. For me it's more about the whole attitude. You know the "reduce, reuse, recycle" saying? Surely pesticides are an area where, with a change in attitude, we can significantly reduce, with all the benefits that it could bring.
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I gave the common salt analogy to provide an idea of the level of toxicity we are talking about. I could have used a whole range of other chemicals, but many people will not have come across them. Salt they do know. It is as you say useful to allow lay people to come to grips with comparative toxicities. Toxicity is a property of the chemical itself and natural chemicals can be just as toxic as synthetic chemicals.
I suspect you don’t understand MSDSs if you think they are advertising. They are intended to give safety information to users. Frankly they tend to be overly conservative recommending unnecessary safety precautions, but given that many users of all sorts of chemicals are untrained in safe handling, this is understandable.
You are correct to question the focus on the LD50 of the active ingredient where exposure is to the formulated product. In the case of simazine, the usual formulation is an SC (suspension concentrate). The other ingredients include dispersion agents like alkylene glycol and suspension agents like diatomaceous earth. In the case of simazine, these other compounds result in reduced acute toxicity of the formulated product compared to the active ingredient.
I work a lot with farmers and quite a bit of our focus is on reducing unnecessary pesticide use. There are 2 main reasons for this, one is the cost and the second is the off-target effects. For example, we work on substituting soft insecticides for broad-spectrum insecticides as much as possible in order to maintain natural enemies in the system. A second example, is growing rust-resistant wheats instead of relying on fungicides. However, there are some areas where the damage from the alternatives are much greater than the damage from the pesticides. One example is the use of glyphosate for pre-seeding weed control instead of tillage.