Sublethal effects carbamates

The inhibition of brain cholinesterase is a biomarker assay for organophosphorous (OP) and carbamate insecticides (Chapter 10, Section 10.2.4). OPs inhibit the enzyme by forming covalent bonds with a serine residue at the active center. Inhibition is, at best, slowly reversible. The degree of toxic effect depends upon the extent of cholinesterase inhibition caused by one or more OP and/or carbamate insecticides. In the case of OPs administered to vertebrates, a typical scenario is as follows sublethal symptoms begin to appear at 40-50% inhibition of cholinesterase, lethal toxicity above 70% inhibition. 

It is very clear, therefore, that there have been many examples of neurotoxic effects, both lethal and sublethal, caused by pesticides in the field over a long period of time. Far less clear, despite certain well-documented cases, is to what extent these effects, especially sublethal ones, have had consequent effects at the population level and above. Interest in this question remains because neurotoxic pesticides such as pyre-throids, neonicotinoids, OPs, and carbamates continue to be used, and questions continue to be asked about their side effects, for example, on fish (Sandahl et al. 2005), and on bees and other beneficial insects (see, for example, Barnett et al. 2007). 

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