QUESTION:

A question concerning the legal aspect of "tank contamination". When a chemical is used that states long sleeves should be worn during the mixing and application, and then that mixture is used but a tiny amount remains in the 1 gallon tank, does that amount equal something called an "incidental amount"? I have not heard a solid answer or line concerning such a concept. It seems to me that after a mixture is diluted with water that the amount of toxicant would be virtually incapable in itself to do noticable harm to a person or animal. Perhaps I am right in a practical sense, and not in a technical sense. For example, if a synergist like Exponent was diluted with water and used and the tank had a LITTLE left in the bottom, and then Bifenthrin was added at a Labeled rate, would the label legally need to be followed for Exponent still? I believe I have read that in a larger tank a certain amount of 'residue' or 'trace amounts' is acceptable.

ANSWER:

Interesting question Chris, and I will say first that I have never heard of anyone in a regulatory position considering the slight residue of a previous product to still be in a tank such that it required you to continue following the label for that previous product. This is, of course, if the tank mixture from the first material is properly used so that the tank is virtually "empty" when you add more water and a second, different pesticide. The reality is that with the sensitive testing capabilities available today a lab could probably detect Product A in that tank even when you have moved onto Product Z (meaning many tankfuls later). Unless you emptied every drop from the tank and thoroughly washed every square inch, including all the plumbing, there will still be miniscule trace amounts somewhere in that tank. But, these would be so slight they would have no consequence on what you do with the next tank of mixed material.

Now, whenever someone asks about "legal" aspects I look for the nearest hiding place, so what is always the best idea is to check with YOUR local regulatory inspectors to get their opinion. They would be the ones who will interpret these things in your geographic area. But, let's explore more of your question, and first is the subject of whether or not a trace amount of a pesticide could possibly harm people, animals, or the environment. The reality may be that the potential for harm from residues left in the tank would be so low as to be unworthy of worrying about, but the second reality is that there are plenty of people who don't agree. Someone could be overly sensitive to a substance, even at an extremely low level. There also could be living organisms in certain environments or habitats that are susceptible to certain chemicals, even down at the parts per trillion level, and it actually is these kinds of organisms used as examples of how trace amounts of pesticides could "harm" the environment. Regardless of the level present all pesticides are still considered toxic.

My second thought is with respect to PPE - personal protective equipment. In pest management by professionals using pesticides the rule of thumb is ALWAYS going to be that you wear long sleeve shirt and long pants unless the Label specifies otherwise. And, if we look at the example you offer for Exponent Insecticide Synergist the Label states that "mixers, loaders, applicators, and other handlers must wear long sleeved shirt and long pants", and it is that word "handlers" that is the key. I am speaking from my knowledge of regulations on this in California, but I'll just betcha that most other states interpret it the same, and that is that anyone potentially exposed to pesticides in their job duties is "handling" pesticides. This could include the shop mechanic whose only job is to repair spray equipment. He never sprays or mixes a drop of pesticide, but by virtue of working on equipment that has pesticide residues on it he is legally handling those pesticides, and is subject to all the same requirements of PPE and training.

Where this could differ, I suppose, would be if you switched from one product to another and the second product's Label had wildly different PPE requirements. But, you should always follow the label guidelines for the material that is going to be mixed in the tank for the next use, within reason of course. If your tank were still half full from the first application and you added more water and a full complimentof Product B, then I think there still would be enough of Product A remaining to be considered an amount worthy of regulating according to its label.

How do I summarize all this? Properly emptied the tank is considered to be "empty", and trace residues would not be an issue for the next tankful of a different material. The PPE you wear is dependent upon the new product in that tank and the Label requirements for it. And, regardless of the concentration, any pesticide should be considered "toxic" and to have the potential to harm someone or something.

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