Dichlorvos between

Gantier, C., Le Calve, S., and Mirabel, P. Henry s law constants measnrements of alachlor and dichlorvos between 283 and 298... 

Although several epidemiological studies have suggested a positive association between dichlorvos exposure and cancer, conclusions are limited because all have involved small study groups and exposure to several agents. In animal studies chronic gavage administration of dichlorvos caused a dose-related increase in papillomas of the forestomach in mice and a dose-related increase in mononuclear-cell leukemia and an increased incidence of pancreatic acinar cell adenomas in male rats. The lARC has determined that there is sufficient evidence for the carcinogenicity of DDVP in experimental animals and inadequate evidence in humans. ... 

T ichlorvos (DDVP, dichlorovinyldimethyl phosphate) was first syn-thesized in the late 1940s, but active investigation of its insecticidal properties was not initiated until 1954. Investigations at that time revealed that low concentrations of the vapor of dichlorvos were toxic to adult mosquitoes and flies and that there appeared to be a relatively wide margin of safety between the insecticidal dose and the concentration required to affect man. 

Figure 11.8 In vitro inhibition of AChE by chlorpyrifos (A), methyl parathion (B), and dichlorvos (C) in the clam, Mcretrix casta. Comparisons were made between the pesticide-treated groups and control T < 0.05 < 0.02. (From Devi, K.P. et al., Bull. Environ. Contam. Toxicol., 74, 250, 2005. With...

Dichlorvos is of moderate acute toxicity, with an oral LD50 value in rodents from 50 to 150mgkg. While the LC50 for inhibiting mammalian brain acetylcholinesterase is similar between dichlorvos and paraoxon (i.e., the active metabolite of parathion), the acute LD50 values for these agents are considerably different, due in part to the more rapid metabolism and elimination of dichlorvos. 

In humans, the plasma cholinesterase appears more sensitive than erythrocyte cholinesterase to inhibition by dichlorvos thus, discrimination between these two activities may be warranted during assessment of exposures. 

Trichlorfon has a low mammalian toxicity. Dichlorvos is more toxic, but the difference in toxicity between insects and vertebrates is very high. It evaporates easily and may be formulated in plastic strips that slowly release the insecticide, killing the insects, but it is apparently harmless to humans. The two compounds have also been widely used to kill salmon ectoparasites, as well as parasites encountered in veterinary medicine. However, they are strong teratogens in some species, disturbing brain development (Mehl et al., 2000), and should therefore be used with care. 

Pesticides as a class contain 2 widely quoted examples of ambiguity between mutagenic activity and carcinogenicity. Dichlorvos (2,2-dichlorovinyl dimethyl phosphate), an organophosphate insecticide, and ziram (bis(dimethyldithio-carbamate)zinc), a dithiocarbamate fungicide, are confirmed bacterial mutagens [13]. 

The apparent IC50 for test compounds differs between the cell lines, possibly reflecting species differences. However, ratios of ICjo values for NTE AChE show similar patterns >40 for m>n-OPIDN-inducing compounds (paraoxon and malaoxon) and those unlikely to cause OPfDN (chlorpyrifos-oxon, dichlorvos. and trichlorphon) low ratios (some <1) for the other compounds, all of which induce OPIDN. IC50 values for inhibition of esterases are lower than those for cytotoxicity. 

Figure 8. Mechanism of the predominant reaction between dichlorvos and DNA...

The first work in the literature named as inhibition BioET was a collaborative work between our laboratory and a French laboratory commanding pesticide analysis. In this work, the BioET was developed, employing an array of inhibition biosensors and ANNs [15]. The array of biosensors was formed by three ampero-metric pesticide biosensors that used different AChE enzymes the wild type from electric eel (EE) and two different genetically modified enzymes (B1 and B394). The system was employed for the simultaneous determination and/or resolution of mixtures of two pesticides, dichlorvos and carbofuran, with mean values of... 

Fig. 25 Correlation results between expected and obtained concentration for (a) dichlorvos and (b) methylparaoxon. Reprinted from [16], with permission from Elsevier...

Later, these concepts were translated into an automated flow-injection system, now using dichlorvos and methylparaoxon pesticide mixture, a more difficult to resolve mixture than the previous ones, given both pesticides are from the same family of organophosphates [16]. Figure 25 displays the performance of the developed device, where it can be observed how dichlorvos can be determined down to the 10 nM level and methylparaoxon down to 200 nM level, both with satisfactory comparison between calculated and expected values (especially for the external test set). 

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