Parathion enhanced degradation

Compounds that affect activities of hepatic microsomal enzymes can antagonize the effects of methyl parathion, presumably by decreasing metabolism of methyl parathion to methyl paraoxon or enhancing degradation to relatively nontoxic metabolites. For example, pretreatment with phenobarbital protected rats from methyl parathion s cholinergic effects (Murphy 1980) and reduced inhibition of acetylcholinesterase activity in the rat brain (Tvede et al. 1989). Phenobarbital pretreatment prevented lethality from methyl parathion in mice compared to saline-pretreated controls (Sultatos 1987). Pretreatment of rats with two other pesticides, chlordecone or mirex, also reduced inhibition of brain acetylcholinesterase activity in rats dosed with methyl parathion (2.5 mg/kg intraperitoneally), while pretreatment with the herbicide linuron decreased acetylcholine brain levels below those found with methyl parathion treatment alone (Tvede et al. 1989). 

Some pesticides and herbicides are degraded more rapidly in acid waters and might have to be applied more often or at higher doses. Others, such as malathion and parathion, are degraded more slowly at low pH levels, and may therefore persist in the environment. Some pesticides that are normally negatively charged can become electrically neutral at lower pH this can enhance the rate at which they are absorbed by plants and animals, and can increase their toxicity. ... 

As was thf case with dieldrin, photodecomposition of C-parathion and Cl-toxaphene was relatively extensive, and the addition of FMN has almost no effect on the enhancing or decreasing the rate of degradation to water-soluble products. Since the organic-soluble products were not analyzed in the case of parathion and toxaphene, it is difficult to speculate on the type of degradation products formed and the pathways involved on... 

Any factors that stimulate the growth of soil microorganisms or that increase the availability of pesticides in soil will enhance the degradation of the chemical. Felsot et al. (1981) found that the persistence of carbofuran was inversely correlated with microbial activity in corn-cropped soils. Tu and Miles (1976) reported that 88% of parathion was lost from soil in 7 months diazinon, 92% lost in 20 weeks paraoxon, 100% hydrolyzed in 12 hr mala-thion, 50-90% lost in 24 hr and carbofuran, 50% lost in 3-50 weeks. 

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