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

flowing water habitats, it is not surprising that pesticide concentrations from these datasets were
generally much lower than predicted by modeling efforts.
Limited applicability to other locations. Pesticide runoff and drift are influenced by a variety of
site-specific variables such as meteorological conditions, soil type, slope, and physical barriers to
runoff and drift. Additionally, surface water variables such as volume, flow, and pH influence
both initial concentrations and persistence of pesticides in aquatic habitats. Finally, cropping
patterns and pesticide use have high spatial variability. Given these and other site-specific
factors, caution should be used when extrapolating monitoring data to other sites.
Representativeness of current and future uses. Pesticide use varies annually depending on
regulatory changes, market forces, cropping patterns, and pest pressure. The use of
cholinesterase inhibiting insecticides has declined in California over recent decades. However,
pesticide use patterns change annually and may result in either increases or decreases in use of
pesticide products for specific uses. There is considerable uncertainty regarding the
representativeness of monitoring conditions to forecast future use of products containing the
three a.i.s.
Lack of information on actual use to correlate with observed concentrations. A common
constraint in the monitoring data was lack of information on actual use of pesticides containing
the three a.i.s. For example, the ability to relate surface water monitoring data to the proposed
action was severely hampered because information on application rates, setbacks/buffers, and
applications methods associated with the monitoring were generally not reported. In most cases,
the temporal and spatial aspect of pesticide use relative to sampling was not reported, further
limiting the utility of the information.
Exposure to Other Action Stressors
Stressors of the action also include the metabolites and degradates of the a.i.s, other active and
inert ingredients included in their product formulations, and tank mixtures and adjuvants
authorized on their product labels. Below we summarize information presented in the BEs and
provide additional information to characterize exposure to these stressors.
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