Carbamate pesticides, toxicity

CARBAMATE PESTICIDES, FLAMMABLE, LIQUID, TOXIC, n.O.S., CARBAMATE PESTICIDES, FLAMMABLE, LIQUID, TOXIC, n.O.S.,... 

Although bicyclophosphates do not inhibit acetylcholinesterase, they exhibit a synergistic toxic effect with materials that do. Individuals who have had previous exposure to cholinesterase inhibitors such as nerve agents and commercial organophosphate or carbamate pesticides may be at a greater risk from exposure to bicyclophosphates. 

Modified from Zakour, H.R. 1980. Toxicity, Uptake and Metabolism of the /V-methyl-carbamate Pesticide Carbofuran by the Freshwater Bivalve Mollusc Glebula rotundata (Lamarck). Ph.D. Thesis, Rice University, Houston. 148 pp. 

Carbamate pesticides can easily be converted to A-nitroso derivatives in the presence of sodium nitrite under acidic conditions. The A-nitroso form of carbofuran could possibly be formed in the human stomach (Nelson et al. 1981). Since carbofuran is used routinely on a variety of crops and nitrite is a common component of the human diet and present in human saliva, nitrosation of carbamates under conditions simulating those in the human stomach is possible. Lijinsky and Schmal (1978) tested nitrosocarbofuran and five other nitrosated carbamate pesticides for carcinogenicity in rats. Nitrosocarbofuran, at 16.5 mg/kg BW administered orally once weekly for 23 weeks, was the most toxic compound tested and caused the death of several animals by liver damage early in the experiment. Among survivors, nitrosocarbofuran was the most carcinogenic,... 

It should be realized that with the exception of a few groups of chemicals (such as some organophosphorous and carbamate pesticides as well as some polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and polychlorinated biphenyls (PCBs), precise mechanistic information on their toxic effects are scarce. In realizing that the exact molecular mechanism is not known for most chemicals the term mode of action is used to describe toxicides that appear to be similar albeit the mechanism is not known in detail, see also Section 4.2.6. For several groups of endocrine disrupters this terminology seems appropriate. 

Carbamate pesticides, liquid, flammable, toxic, n.o.s., flashpoint less than 23 °C. 2758... 

Acetylcholine is a neurotransmitter that functions in conveying nerve impulses across synaptic clefts within the central and autonomic nervous systems and at junctures of nerves and muscles. Following transmission of an impulse across the synapse by the release of acetylcholine, acetylcholinesterase is released into the synaptic cleft. This enzyme hydrolyzes acetylcholine to choline and acetate and transmission of the nerve impulse is terminated. The inhibition of acetylcholineasterase results in prolonged, uncoordinated nerve or muscle stimulation. Organophosphorus and carbamate pesticides (Chapter 5) along with some nerve gases (i.e., sarin) elicit toxicity via this mechanism. 

Synonyms isocyanic acid methyl ester, isocyanatomethane, MIC Formula CH3NCO MW 57.05 CAS [624-83-9] used in the manufacture of carbamate pesticides colorless liquid with an unpleasant odor boils at 39°C freezes at -80°C vapor pressure 400 torr at 20°C density 0.96 g/mL at 20°C vapor density 1.97 (air= 1) decomposes in water soluble in most organic solvents highly toxic and flammable. 

Carbamate pesticides are used as (1) insecticides, (2) fungicides and (3) herbicides. Insecticides are generally derived from carbamic acid fungicides, from thiocarbamic acid. The herbicide carbamates are a more complex class of compounds. Tables 21 and 22 list some commercial carbamate pesticides in approximate order of decreasing toxicity. It should be noted that the relative classification of highly and moderately toxic is no measure of the relative carcino-, muta- or teratogenicities of these carbamates, since it is based solely on acute LD q data (Morgan, ref. 20). 

Carbamates effect the reversible carbamylation of acetylcholinesterase, permitting accumulation of acetylcholine at cholinergic neuroeffector junctions (muscarinic effects), at the myoneural junctions of skeletal muscle, and in the autonomic ganglia (nicotinic effects). CNS function is also impaired. However the relatively large dissociation constant of the carbamyl-enzyme complex indicates that it dissociates more readily than does the organophosphate-enzyme complex, mitigating the toxicity of the carbamate pesticides. The reversibility of the carbamyl-enzyme complex affects (limits) the utility of blood enzyme measurements as a diagnostic tool. 

While the depression of plasma and/or RBC cholinesterase may be detected after exposure to very large amounts of carbamates, enzyme activity usually recovers rapidly--within minutes to hours. Hence these tests can be misleading unless one of the rapid methods for testing cholinesterase activity has been employed. A more sensitive and specific absorption test for several of the carbamate pesticides is the measurement of their metabolites in the urine within 48 hours of exposure. Carbamate pesticides are sufficiently acutely toxic that those attending the victim must avoid contact with contaminated apparel or vomitus, and should wear rubber gloves during decontamination of hair and skin of the victim. 

Table 22. Moderately Toxic Commercial Carbamate Pesticides...

Carbamate pesticides A salt or ester of carbamic acid used as a pesticide and known to cause death of animals at high concentrations. Aldicarb is effective against thrips, aphids, spider mites, lygus, fleahoppers, and leafminers but is mainly used against nematodes. Carbofuran is the most toxic of the carbamate pesticides used to control insects in potatoes, corn, and soybeans. Carbaryl kills beneficial insect and crustacean species along with the target pests. 2-(i-Methylpropyl)phenyl methylcarbamate is used as an insecticide on rice and cotton. 

Aminocarb is a nonsystemic insecticide. It controls lepidopterous insects, aphids, and soil mollusks. The acute oral LD50 for rats is 50 mg/kg, and the acute dermal LD50 for rats is 275 mg/kg, suggesting that toxicity to skin is appreciably severe compared with carbamate pesticides.2... 

Pesticide is used to control pests of different kinds, such as target insects, vegetation, and fungi. Pesticides are known poisons used specifically for the control of crop pests and rodents. Some are very poisonous, or toxic, and may seriously injure or even kill humans. Others are relatively nontoxic. Pesticides can irritate the skin, eyes, nose, or mouth. The health effects of pesticides depend on the type of pesticide. The organophosphate and carbamate pesticides affect the nervous system. Others cause irritation to the skin, eyes, and mucous membranes. Several pesticides are carcinogens and some others cause disturbances to the hormone or endocrine system in the body. 

Pelkonen, O., Vahakangas, K., Gupta, R.C. (2006). Placental toxicity of organophosphate and carbamate pesticides. Toxicology of Organophosphate and Carbamate Compounds (R.C. Gupta, ed.), pp. 463-79. Elsevier Academic Press, New York. 

Exposure to a toxic dose of OP results in inhibition of acetylcholinesterase and butyrylcholinesterase activities. The most common method to measure OP exposure is to assay acetylcholinesterase and butyrylcholinesterase activities in blood using a spectrophotometric method (EUman et al, 1961 Wilson et al, 2005 Worek et al, 1999). The drawbacks of activity assays are that they do not identily the OP. They show that the poison is a cholinesterase inhibitor but do not distinguish between nerve agents, OP pesticides, carbamate pesticides, and tightly bound, noncovalent inhibitors like tacrine and other anti-Alzheimer drugs. In addition, low-dose exposure, which inhibits less than 20% of the cholinesterase, carmot be determined by measuring acetylcholinesterase and butyrylcholinesterase activity because individual variability in activity levels is higher than the percent inhibition. 

The overall toxicity profile of the carbamate pesticides covers a wide spectrum from virtually nontoxic to some of the most highly toxic pesticides in commercial use carbamate LD50 values can range from 5000 to lmgkg . More than 50 commercially available carbamate pesticides are in use today with... 

In general, carbamates are not markedly toxic to wildlife. In higher doses, however, carbamate usage has the potential to produce ecotoxicity. When applied directly to the soil, many carbamates will cause significant reduction in microflora and worms. Bees are also especially sensitive to some carbamate pesticides. Because there is very little bioaccumulation of carbamate pesticides, the threats to wildlife are usually through direct exposure after application rather than through the food chain. Note that there have been reports of wildlife morbidity and mortality even if applications of certain carbamate pesticides were made at the recommended rate. 

All dithiocarbamates have moderate to low acute toxicity. As opposed to carbamate pesticides, exposure to... 

Nematoddes are pestiddes that kill parasitic worms such as roundworms or threadworms. Early ne-matocides were used as soil fumigants. Since the 1960s, a completely new group of nonfumigant ne-matocides has been developed. All are organophos-phorus or carbamate pesticides with marked (acute oral and dermal) toxicity to humans. 

See also Carbamate Pesticides Chiorophenoxy Herbicides Federai Insecticide, Fungicide, and Rodenticide Act, US Nematocides Occupationai Toxicoiogy Organo-chiorine Insecticides Organophosphates Poiiution, Soii Poiiution, Water Psychoiogicai Indices of Toxicity Pyre-thrins/Pyrethroids Veterinary Toxicoiogy. 

Human natural killer (NK) lymphocytes are vital to immune system defense against viral infection. They are also crucial in protecting against primary tumor formation. In vitro exposures to low levels of two organotin pesticides, tributyltin (4.76) and triphenyltin (4.19), and two carbamate pesticides, maneb (0.62) and ziram (1.23), produced significant loss of cytotoxic function of NK cells after 6 days of exposure. The toxicities of the pesticides also increased very significantly with exposure durations J51 It should be noted that exposure to ziram can come from other sources. It is used as an additive in rubber products such as latex gloves. 

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