Herbicides parathion

The detection limits for 2,6-dinitroaniline herbicides are between 20 and 200 ng substance per chromatogram zone (Table 1). Similar results are also obtained with methyl and ethyl parathion (pink-colored zones). 

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). 

Holmstedt (1959) and Brown and Muir (1971) have reviewed perocular absorption of pesticides. More recently, Sinow and Wei (1973) have shown that the quartemary herbicide paraquat can be lethal to rabbits if applied directly to the surface of the eyes. Parathion, in particular, is exceedingly toxic when administered via the eye, a concern that must be kept in mind for the protection of pesticide applicators. 

Phenol and substituted phenol compounds (Fig. 19) are known to be widespread as components of industrial wastes. These compounds are made worldwide in the course of many industrial processes, as for example in the manufacture of plastics, dyes, drugs, and antioxidants, and in the pulp and paper industry. Organophosphorus and chlorinated phenoxyacids also yield chlorinated and nitrophenols as major degradation products. 4-Nitrophenol was reported as a breakdown product after the hydrolysis and photolysis of Parathion in water and chlorinated phenols are formed by the hydrolysis and photolysis of chlorinated phenoxyacid herbicides [251-253]. 

Because each herbicide may degrade during volatilization, it is interesting to compare the cumulative volatilization of the parent contaminant and its metabolites. This behavior was studied in a wind-tunnel experiment by Wolters et al. (2003) for a mixture of parathion, terbuthylazine, and fenpropimorph, as well as for the metabolites fenpropimorph acid and desethyl-tetrabuthylazine. Figure 8.6... 

Crop protection chemicals are an important group of contaminants that exhibit biologically mediated transformation in aerobic or anaerobic subsurface environments. We consider two well-known contaminants the insecticide parathion, which is an organophosphate compound, and the herbicide atrazine, from the triazine group. 

Activated carbon studies on widely used herbicides and pesticides have shown that it is successful in reducing the concentration of these toxic compounds to very low levels in wastewater [16]. Some examples of these include BHG, DDT, 2,4-D, toxaphene, dieldrin, aldrin, chlordane, malathion, and parathion. Adsorption is affected by many factors, including... 

Estimate the Kiow values at 25°C of (a) ethylacetate, (b) 2,3,7,8-tetrachloro-dibenzodioxin, (c) the herbicide 2-s-butyl-4,6-dinitrophenol (Dinoseb), (d) the insecticide parathion, and (e) the hormone testosterone using solely the fragment coefficients and correction factors given in Tables 7.4 and 7.5 (Eq. 7-15). 

Broad range of herbicides and insecticides (atrazine, bromacil, carbofuran, 2-4- D, DDT, diuron, malathion, methyl parathion, simazine)... 

Studies of reproductive and teratogenic effects of OPPs on humans are few. Gordon et al. (1981) found stronger correlations of cleft lip and palate malformations for insecticides and/or herbicides than for all other agrichemicals combined. The post mortem examination of women s ovaries following acute intoxication revealed adverse ovarian effects from parathion and both infertility and menstrual disturbances were observed in female applicators of OPPs. Also, women from fruit growing areas exposed to OPPs experienced earlier menopause, infertility and other functional irregularities—e.g., in the liver and nervous system and in bile production. 

OPs are chemicals used in agriculture as acaricides, herbicides, and insecticides (Appendix 5-A-l). Because of their toxicity, several of these chemicals are being phased out from use parathion (ethyl) is an example. Many have been now classified by the United States Environmental Protection Agency (USEPA) as a restricted use pesticide (RUP) or a general use pesticide (GUP). Pesticide chemistry has taken a turn for the synthesis, manufacture, and use of still safer compounds. A list of OPs considered for banning has been identified by the USEPA (Table 5-3). The following pages will briefly discuss the uses and toxicity of different OPs. 

The organophosphosphates represent another extremely important class of organic insecticides. They were developed during World War II as chemical warfare agents. Early examples included the powerful insecticide schradan, a systemic insecticide, and the contact insecticide parathion. Unfortunately, both of these compounds are highly poisonous to mammals and subsequent research in this field has been directed toward the development of more selective and less poisonous insecticides. In 1950, malathion, the first example of a wide-specUnm organophosphorus insecticide combined with very low mammalian toxicity, was developed. And at about the same time the phenoxyacetic acid herbicides were discovered. These systemic compounds ate extremely valuable for the selective control of broad-leaved weeds in cereal crops. These compounds have a relatively low toxicity to mammals and are therefore relatively safe to use. 

A close examination of this usage table shows that the herbicide atrazine has held the number one spot for the last 20 years. This compound is often used in nonfood crops such as cotton. However, some compounds are notably absent from the 1993 tabulation, including toxaphene, methyl-parathion, car-baryl, propachlor, DSMA, linuron, aldrin, carbofuran, chloramben, maneb, sodium chlorate, propanil, DBCP, malathion, dinoseb, and chlordane. It should also be noted that DDT, the pesticide on which Silent Spring was focused and which continues to be used as the example of man s folly with chemicals, is not on either list. The one generalization that can be made concerning this fist of deletions is that most of these pesticides are more persistent than the compounds that replaced them and a significant number of them are chlorinated hydrocarbons. It is important to keep these compounds in mind since popular press accounts of pesticide contamination often quote incidences of exposure to unnamed pesticides and then focus most discussion... 

Some toxic substances, such as cyanide, heavy metals, or herbicides, alter or destroy enzymes so that they function improperly or not at all. Toxicants can affect enzymes in several ways. Heavy metals, for example, tend to bind to sulfur atoms in enzymes, thereby altering the shape and fnnction of the enzyme. On the other hand, insecticide parathion bonds covalently to the nerve enzyme acetylcholinesterase, which can then no longer serve to stop nerve impulses. 

German scientists, undertaking experiments nerve gas during World War II, synthesized the organophosphorus insecticide, parathion, which was marketed in 1943. The phenoxyacetic acid herbicides 2,4-D and 2,4,5-T, were also marketed during the 1940s. 

Approximately 125 companies manufacture more than 60 technical grade pesticides in India, including Dirty Dozen pesticides BHC, DDT and methyl parathion, with an estimated total production capacity of 126,000 tonnes. In the 12 months leading up to March 1996, companies in India produced 86,000 tonnes of pesticides and the volume of pesticides sold in India rose by 5% to 83,400 tonnes, including 18,000 tonnes of HCH. Insecticides were 67% of the market, fungicides 22% and herbicides 10%. The next year to March 1997 saw a growth of 7.5% in value of the Indian pesticide market to US 602 million. 

The herbicide atrazine is not toxic to midge (Chironomus tentans) larvae but has a strong synergistic effect on several organophosphorus insecHcides such as chlorpyrifos and parathion-methyl, but not to malathion. The increased rate of oxidahon to the achve toxicants, the oxons, is suggested as one of the mechanisms, and the level of CYP enzymes is elevated. Figure... 

Of the 19 pesticides grouped in Table II, all were negative in five Phase I bioassays and the Phase 2 bioassays performed. These compounds included insecticides (I), fungicides (F), and herbicides (H). Malath ion, parathion, pentachloronitrobenzene (PCNB), and phorate were also negative for heritable chromosomal effects in the mouse dominant lethal test. The six compounds grouped in Table III that were positive in three or more bioassays were acephate, captan, demeton, folpet, monocrotophos, and trichlorfon. Positive results were seen for demeton in all in vitro tests in Phase 1 and Phase 2. Folpet and captan were positive in all Phase 1 and all Phase 2 in vitro assays except the test for unscheduled DNA synthesis in WI-38 cells. Trichlorfon was positive in all Phase 1 and Phase 2 in vitro tests, with the exclusion of relative toxicity tests with E coli and subtiI is. 

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