Solvent Effects on Toxicity, Reaction of Certain Phosphorothionate Insecticides with Alcohols and Potentiation by Breakdown Products

Abstract

fed 3.5 kg. per day. Correlation of Blood and Milk Bromide LevelsThe correlations between blood and milk bromide levels where the cows were fed sodium bromide or grain fumigated with methyl bromide are plotted for comparison in Figure 1. Although the slopes of the regression curves are slightly different, they indicate similarity between the sources of bromide with respect to blood-milk bromide level relationships. ConclusionsWhen dietary bromide is held at a steady concentration, an equilibrium is established with respect to milk bromide levels. The time of equilibration appears to be about 20 to 30 days.Lactating cows fed a methyl bromide fumigated grain ration at the rate of 1 pound of ration to each 4 pounds of milk produced will secrete milk having increased levels of bromide as follows: /n Crain in Milk 53 4 to 12 100 7 to 12 220 10 to 20Literature Cited(1) Dow Chemical Co., unpublished data.

Toxicological Properties of the Organophosphorus Insecticide Dimethoate

“…Such reactions have been observed in 2-methoxyand 2-ethoxy-ethanol Sanderson, 1961, 1963) and in isopropanol. Any changes in other solvents are slow and are probably due to contact with moist air (see later).…”

“…of dimethoate CH3-0 S p CH3 0 S CH2 CO NHWCH3 however, E.P.N., tri-o-cresyl phosphate, and tri-ocresyl phosphorothionate did potentiate dimethoate (Seume and O'Brien, 1960). Sanderson (1961, 1963) have shown also that the difference in toxicity between pure dimethoate and other grades (Table 2) is due to a trace impurity, present in the other grades, which potentiates the toxicity of pure dimethoate. The impurity responsible is thought to be produced by partial hydrolysis according to the equation:-…”

“…After nine months' storage under tropical conditions of a trial formulation in 2-methoxyethanol, the acute oral LD50 to rats fell to 15 mg./kg. Further investigation Sanderson, 1961, 1963) indicated that the effect was due to the exchange reaction noted in the Introduction, and a reaction product with 2-methoxyethanol was isolated with an acute oral LD50 to rats of about 1 mg./kg. Changes in other alcoholic solvents, such as propylene glycol, were much less, and in non-hydroxylic solvents the stability of solutions was comparable with that of undissolved dimethoate; toxicity eventually fell very slowly due to hydrolysis of the active ingredient.…”

Residue Reviews

“…Two other factors may be important here. CASIDA and SANDERSON (1963) suggested that an insecticide may react with a solvent or substrate or a break-down product to produce more toxic materials, and gave several examples of such reactions by phosphorothionate insecticides. Again, LICHTENSTEIN et al (1967) examined the effect of a detergent on residues, the persistence and toxicity of parathion and diazinon being found to increase in pea plants when a detergent was added to the growing medium.…”

Residue Reviews / Rückstands-Berichte

“…In early formulations, dimethoate reacted during storage with solvents of the 2-alkoxy methanol type to yield a product of higher toxicity (CASIDA and SANDERSON 1963). Oxidation to more toxie products during storage may occur with certain of the phosphorothioates.…”