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

(e.g., survival, growth, etc.). The information provided by EPA addressed aspects of survival,
growth and reproduction of aquatic species (freshwater and saltwater), as well as providing some
discussion on other information found in the open literature, such as results from some field
experiments and experiments that evaluated sublethal effects. NMFS is charged under the ESA
to evaluate all direct and indirect effects of an action. We therefore evaluate all aspects of an
action that may reduce fitness of individuals or reduce primary constituent elements of
designated critical habitat. The evaluation includes information that EPA provided on survival,
growth, or reproduction, but also encompasses a broader range of endpoints including behaviors,
endocrine disruption, and other physiological alterations. The information we assessed is
derived from published, scientific journals and information from government agency reports,
theses, books, information and data provided by the registrants identified as applicants, and
independent reports. Typically, the most relevant study results are those that directly measure
effects to an identified assessment endpoint derived from experiments with salmonids, preferably
listed Pacific salmonids or hatchery surrogates, exposed to the stressors of the action.
Figure 37. Response analysis
Mode and Mechanism of Action
Effects of pesticide products on
ESA-listed species and their habitat
Individual
responses
Response Profile
Habitat
responses
Carbaryl, carbofuran, and methomyl share a similar mode and mechanism of toxic action and are
a part of a group known as N-methyl carbamates. All three have similar chemical structures and
act as neurotoxicants by impairing nerve cell transmission in vertebrates and invertebrates. They
inhibit the enzyme AChE, which is present in cholinergic synapses. The normal function of
AChE is to break down (hydrolyze) the neurotransmitter, acetylcholine, thereby serving as an
“off-switch” for the electrochemical signal transmissions along nerve cells and neuromuscular
junctions. AChE is prevalent in a variety of cell and organ types throughout the body of
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