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Carbaryl, Carbofuran, and Methomyl - National Marine Fisheries ...

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isk assessment. With these <strong>and</strong> other mitigation measures for these individual<br />

pesticides, EPA concluded that the cumulative risks to humans associated with the Nmethyl<br />

carbamates are below EPA’s regulatory level of concern<br />

(http://www.epa.gov/pesticides/cumulative/carbamate_risk_mgmt.htm). The FQPA does<br />

not address cumulative risk of pesticides to aquatic resources.<br />

Figure 1. Stressors of the Action<br />

Registration <strong>and</strong> uses of pesticide labels<br />

containing the a.i.s (a.i.) carbaryl,<br />

carbofuran, <strong>and</strong> methomyl<br />

Metabolites of carbaryl, carbofuran,<br />

methomyl<br />

Degradates of carbaryl, carbofuran,<br />

methomyl<br />

Other ingredients in formulations<br />

Label-recommended tank mixtures<br />

Adjuvants/surfactants added to<br />

formulations<br />

Mode of Action of Carbamate Insecticides. NMC insecticides are neurotoxicants,<br />

affecting the central <strong>and</strong> peripheral nervous systems of animals. Similar to other<br />

carbamate <strong>and</strong> organophosphate (OP) insecticides, these a.i.s inhibit the enzyme<br />

acetylcholinesterase (AChE) found in brain <strong>and</strong> muscle tissue of invertebrates <strong>and</strong><br />

vertebrates. Thus, NMCs belong to a class of insecticides known as AChE inhibitors.<br />

Inhibition of AChE results in a build-up of the neurotransmitter, acetylcholine, which can<br />

lead to continued stimulation. Normally, acetylcholine is broken down rapidly in the<br />

nerve synapse by AChE. Chemical neurotransmission <strong>and</strong> communication are impaired<br />

when acetycholine is not quickly degraded in animals, which ultimately may result in a<br />

number of adverse responses from physiological <strong>and</strong> behavioral modification to death.<br />

19

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