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

Summary of Toxicity Information Presented in the Biological Evaluations
Each BE primarily summarized acute and chronic toxicity data from “standardized toxicity tests”
submitted by pesticide registrants during the registration process, tests from government
laboratories available in EPA databases, or from published, peer-reviewed scientific publications
(books and journals). The assessment endpoints from these tests for an individual organism
generally included aspects of survival (death), reproduction, and growth measured in laboratory
dose-response experiments (EPA 2004). Survival is measured in both acute and chronic tests.
Reproduction and growth are generally measured and reported in the chronic tests. Populationlevel
endpoints and analyses were generally absent in the BEs, other than a few measurements of
fish and aquatic invertebrate reproduction. Adverse effects to organisms were not translated into
consequences to populations. The BEs also presented some information on multispecies
microcosm and mesocosm studies. For this Opinion, NMFS translates effects to individual
salmonids into potential population-level consequences as explained in the Risk Characterization
portion of the Effects of the Proposed Action section, and ultimately draws a conclusion on the
likely risk to listed salmonids based on exposure and anticipated individual and population-level
effects.
Survival of individual fish is typically measured by incidences of death following 96 h exposures
(acute test) and incidences of death following 21 d, 30 d, 32 d, and “full life cycle” exposures
(chronic tests) to a subset of freshwater and marine fish species reared in laboratories under
controlled conditions (temperature, pH, light, salinity, dissolved oxygen, etc.,) (EPA 2004).
Lethality of the pesticide is usually reported as the median lethal concentration (LC50), the
statistically-derived concentration sufficient to kill 50% of the test population. For aquatic
invertebrates it may be reported as an EC50, because death of these organisms may be difficult
to detect and immobilization is considered a terminal endpoint. An LC50 is derived from the
number of surviving individuals at each concentration tested following a 96 h exposure and is
typically estimated by probit or logit analysis and recently by statistical curve fitting techniques.
In FIFRA guideline tests, LC50s are typically calculated by probit analysis. If the data are not
normally distributed for a probit analysis, than either a moving average or binomial is used,
resulting in no slope being reported. Ideally, to maximize the utility of a given LC50 study, a
slope, variability around the LC50, and a description of the experimental design- such as
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