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

Assessment endpoint: Fish survival
Assessment measure: 96 h survival from laboratory bioassays reported as an LC50.
Carbofuran is the most toxic of three insecticides based on fish survival values (LC50s) followed
by carbaryl and methomyl, respectively (Table 64). All three carbamates have a range of acute
freshwater fish LC50s spanning 1 to 2 orders of magnitude. EPA reported the following ranges
of LC50s: carbofuran LC50s ranged from 88-3,100 μg/L; carbaryl LC50s ranged from 250-
290,000 μg/L; and methomyl LC50s ranged from 300-7,700 μg/L. Based on these LC50 ranges,
EPA classified these insecticides as “highly toxic” to “moderately toxic”. Salmonids were well
represented in the data set, with 11 results for carbaryl, 11 for carbofuran, and 13 for methomyl.
A cumulative frequency distribution of carbaryl LC50s for freshwater fish indicated that Atlantic
salmon were the most sensitive of the species tested, and salmonids as a group were much more
sensitive than fathead minnow and bluegill sunfish (EPA 2003).
EPA classified the three carbamates as very highly toxic to moderately toxic to estuarine and salt
water species depending on the chemical and the fish species tested. Carbofuran LC50s for
marine and estuarine fish ranged from 33 μg/L to more than 100 μg/L (n=5), indicating that
saltwater/estuarine species were more sensitive to carbofuran than salmonids tested in
freshwater. Two LC50s (2,200 and 2,600 μg/L, both sheepshead minnow) were reported for
carbaryl and one LC50 (1,160 μg/L, sheepshead minnow) was reported for methomyl. Based on
available data presented in EPA documents, it is uncertain whether marine and estuarine species
are more sensitive, less sensitive, or equally sensitive to carbaryl and methomyl compared to
freshwater fish. No data were presented on salmonids exposed in saline environments.
Assessment endpoint: Reproduction
Assessment measure: Number of offspring, hatchability, number of fish that attained sexual
maturity by 136 d, and number of spawns per spawning pair
For carbaryl, one chronic study was listed in the BE (EPA 2003) and briefly discussed in the
Science Chapter (EPA 2003), which evaluated a variety of assessment endpoints of fathead
minnows including reproductive endpoints (referenced in (EPA 2003) as TOUCAR05 Carlson
1972, although this is an erroneous citation of (Carlson 1971)). Reproductive endpoints
measured included number of mature males, number of mature females, number of immature
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