Pesticide potency

Pesticides. Many pesticides are highly concentrated and are in a physical form requiring further treatment to permit effective appHcation. Typically carriers or diluents are used (see Insectcontroltechnology). Although these materials are usually considered inert, they have a vital bearing on the potency and efficiency of the dust or spray because the carrier may consist of up to 99% of the final formulation. The physical properties of the carrier or diluent are of great importance in the uniform dispersion, the retention of pesticide by the plant, and in the preservation of the toxicity of the pesticide. The carrier must not, for example, serve as a catalyst for any reaction of the pesticide that would alter its potency. 

Dixon LA. 1998. Potency of combined estrogenic pesticides Synergy between synthetic oestrogens. Chemtracts Org Chem 11 306-308. 

Hard evidence for the first category seems to be nonexistent. An educated guess on the potential hazards would combine residue technology [how much of a secondary amine (or amide, urea, carbamate, etc.) might a person consume or otherwise be exposed to ], nitrosation chemistry (what would be the yield of in vivo nitrosation of the pesticide thus consumed ), and toxicology (what would be the toxicological effect and potency of the nitroso compound thus formed ). Frequently, these questions, which simplify to, "What dose—eg., in mg/kg—of a pesticide-derived nitroso compound might a person be exposed to and what would be the result if he were " are not carefully considered. 

Kavita Ramamoorthy. Potency of Combined Estrogenic Pesticides. Science. 275 (Jan. 17, 1997) 405. 

Many activations involve compounds which are used as pesticides. In the case of N-nitrosation, the precursors are secondary amines and nitrate. The former are common synthetic compounds and the latter is an anion found in nearly all solid and aqueous phases. The N-nitrosation of a secondary amine [R-NH-R ] occurs in the presence of nitrite formed microbiologically from nitrate. The product is an N-nitroso compound (i.e., a nitrosamine [RR -N-N=0]). The reason for concern with nitrosamines is their potency, at low concentrations, as carcinogens, teratogens, and mutagens. 

The UK Pesticide Safety Directorate (PSD) has decided to use the TEF approach for assessment of combined risk from exposure to mixtures of acetyl cholinesterase inhibitors (organophosphate (OP) compounds and carbamates) (PSD 1999). Despite clear differences in the action of carbamates and OP compounds, the index compounds selected for all acetyl cholinesterase inhibitors were either aldicarb (carbamate) or chlorpyrifos (OP). The POD for determining relative potency was predetermined as the dose level that produced 20% inhibition of red blood cell cholinesterase in a 90-day dietary study in rats. 

This group of compounds is used as pesticides and nerve gases. The structure and therefore metabolism and potency varies. However, they all act in a similar manner. There are two toxic effects, cholinesterase inhibition and delayed neuropathy, but all OPs do not necessarily cause both. The cholinesterase inhibition results from the similarity between the organophosphorus compound and acetylcholine. The organophosphorus compound therefore acts as a pseudosubstrate but blocks the enzyme, in some cases, permanently. This is because the... 

Control of plant diseases by homeopathic potencies would not only eliminate pesticidal residues in treated plants but also do away with environmental pollution in the agroecosystem. For this, new materia medica in relation to plants should be developed by drug proving on plants and by merging plant pathology with toxicology. 

USEPA] US Environmental Protection Agency. 2003b. Developing relative potency factors for pesticide mixtures biostatistical analyses of joint dose-response. EPA/600/R-03/052, ORD/NCEA. Cincinnati (OH) US Environmental Protection Agency. 

A method to set REIs would account for the rate of dermal absorption, the rate of foliar contact and the rate of change in cholinesterase. These factors were used in the Popendorf and Leffingwell (1982) Unified Field Model for determining REIs. This model also accounts for the relative rate of DFR dissipation, and differences in potency based on the dermal LD50 of the pesticide. The Unified Field Model is an elegant technique that takes into account many variables affecting exposure and cholinesterase inhibition as a response. Ultimately, the rate of cholinesterase inhibition, and not a fixed level of inhibition, is the primary... 

Probably the most discussed factor is the possibility of a broad-spectrum reactivator. Every new oxime could be tested for its broad-spectrum potency. However, the probability of finding such an oxime is low. Alternately, we can use a combination of two oximes. Such an approach was already applied in the former Yugoslavia (Kovacevic et al, 1989a, b) two decades ago. Candidates for this approach should be oxime HI-6 and various other oximes which are applicable in the case of tabun and pesticide poisoning. 

Over the last decades, large amounts of different man-made chemicals which can act as weak estrogens have been released into the terrestrial and aquatic environment and are distributed world-wide. Classical environmental estrogens are pesticides, such as o,p -DDT, and its metabohtes o,p -DDE and o,p -DDD, methoxychlor and its metabolites, chlordecone (Kepone ), dieldrin, Toxaphene, and endosulfan [126, 135, 136]. It is also known that many chemicals with very weak or no measurable estrogenic activity can be metabolized in organisms especially to hydroxylated compounds which may have much more estrogenic potency than the parent compound. Examples are methoxychlor and its mono- and di-demethylated derivatives [126,127] as well as the alkylphenol... 

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