How do pesticides change?if they change what do you think about it?
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The EPA categories are rather broad, so another way to look at this is to “weight” the amounts based on their relative oral toxicity. In the graph to the right I have taken the foliar, non-sulfur numbers and multiplied them all by the value 500/Oral ALD50. 500mg/kg is the dividing line between “slightly” and “moderately” toxic in the EPA categories. Thus a product with a toxicity of 4000 mg/kg is counted as 1/8th of its weight in pounds. A product with a toxicity of 40mg/kg is counted as 12.5 times its weight in pounds.
From this approach we see that even though almost three times as many pounds of foliar applied, non-sulfur pesticides are being used on grapes in recent years, there has really been no increase in the overall “toxic load” involved.
In the 22 years covered by this data set, there have been some dramatic changes in the nature of pesticides used. The crop and product in this case may be quite special (and delicious), but the trend is not unique to wine grapes. We would see a similar change in most crops. This sort of change didn’t happen by accident. It represents a great deal of work by a diverse collection of players in the public and private sphere. I’ll go into that in detail in the next post in this series. There are many dimensions of toxicity, but the most basic is how toxic something is when consumed. This is what would be of concern for pesticide residues. This is called Acute Oral Toxicity and it is determined by feeding different amounts of a chemical to a population of rats or mice. The dose relative to the animal’s body weight that kills 50% of the subjects getting that dose is called the LD50. It is expressed as milligrams of chemical per kilogram of body weight. For these numbers the larger the value, the less toxic the compound. For reference, table salt has an oral ALD50 of 3,000 mg/kg. For a 120 pound (54 kg) person that would mean a toxic dose of 163 grams which is about 1/4 of a normal, 1 pound canister of salt. For that same person, the toxic dose of caffeine (oral ALD50 191 mg/kg) would be 10.4 grams – what one would get from 32 servings of nice coffee at Starbucks. In both cases, the salt or coffee would need to be consumed very quickly to achieve that dose. Some of the most toxic insecticides ever used had oral ALD50s in the range of 5-10 mg/kg. Most pesticides today have oral ALD50s of more than 5,000 mg/kg (Category IV) and are less toxic than table salt, vinegar, citric acid, vanillin and many other familiar food ingredients.
From this approach we see that even though almost three times as many pounds of foliar applied, non-sulfur pesticides are being used on grapes in recent years, there has really been no increase in the overall “toxic load” involved.
In the 22 years covered by this data set, there have been some dramatic changes in the nature of pesticides used. The crop and product in this case may be quite special (and delicious), but the trend is not unique to wine grapes. We would see a similar change in most crops. This sort of change didn’t happen by accident. It represents a great deal of work by a diverse collection of players in the public and private sphere. I’ll go into that in detail in the next post in this series. There are many dimensions of toxicity, but the most basic is how toxic something is when consumed. This is what would be of concern for pesticide residues. This is called Acute Oral Toxicity and it is determined by feeding different amounts of a chemical to a population of rats or mice. The dose relative to the animal’s body weight that kills 50% of the subjects getting that dose is called the LD50. It is expressed as milligrams of chemical per kilogram of body weight. For these numbers the larger the value, the less toxic the compound. For reference, table salt has an oral ALD50 of 3,000 mg/kg. For a 120 pound (54 kg) person that would mean a toxic dose of 163 grams which is about 1/4 of a normal, 1 pound canister of salt. For that same person, the toxic dose of caffeine (oral ALD50 191 mg/kg) would be 10.4 grams – what one would get from 32 servings of nice coffee at Starbucks. In both cases, the salt or coffee would need to be consumed very quickly to achieve that dose. Some of the most toxic insecticides ever used had oral ALD50s in the range of 5-10 mg/kg. Most pesticides today have oral ALD50s of more than 5,000 mg/kg (Category IV) and are less toxic than table salt, vinegar, citric acid, vanillin and many other familiar food ingredients.
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