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

high water solubility, low Kow, and a relatively low bioconcentration factor (2-12), fish
are most likely to be exposed to carbofuran through direct uptake from the water column
(Table 45). Exposure via the food chain, pore water, and sediment pathways are also
possible but are less likely to be relevant for most life stages of fish (EPA 2004).
Table 45. Environmental fate characteristics of carbofuran (EPA 2004).
Parameter Value
Water solubility 700 mg/L
Vapor pressure 6 x 10 -7 torrs
Henry's law constant No data
Octanol/Water partition Kow = 0.03
Hydrolysis (t1/2) pH 6, pH 7, pH 7, & pH 9 Stable, 28 days, 3 days, and 0.8-15 hrs
Aqueous photolysis (t½) 6 days
Soil photolysis (t½) 78 days
Aerobic soil metabolism (t½) 321 days
Anaerobic soil metabolism (t½) 624 days
Aerobic aquatic metabolism (t½) No data
Anaerobic aquatic metabolism (t½) No data
Koc
9 to 62 ml/g
Carbofuran is highly mobile and can leach to ground water in many soils or reach surface
waters via runoff. The median K of carbofuran is 30 and the Freundlich coefficient (K )
oc f
ranges from 0.10 to 30.3 (EPA 2004). Major factors influencing the fate and persistence
of carbofuran are water and soil pH. Carbofuran is very mobile and persistent in acidic
environments, but dissipates more rapidly in pHs that are basic. Carbofuran is stable to
hydrolysis at pHs < 6, but becomes increasingly susceptible to hydrolysis as the pH
increases, hydrolyzing rapidly in alkaline aquatic environments (EPA 2004). A study
evaluating its persistence in natural surface waters found it took 3 weeks to degrade by
50% (Sharom, Miles et al. 1980). Carbofuran phenol (7-phenol) was the only degradate
detected in hydrolysis studies (EPA 2004). The rate of carbofuran degradation in soils is
also pH dependent. In an acidic soil (pH 5.7), carbofuran dissipated with a half-life of
321 d, but when the soil was limed to a pH of 7.7, the half-life dropped to 149 d. The
major identified degradate was 3-keto carbofuran, which peaked at 12% of the amount
applied after 181 d. The other degradation products formed during photolysis, soil, and
aquatic metabolism studies are 3-hydroxycarbofuran, 3-hydroxy-7-phenol, and 3-keto-7phenol
(EPA 2004).
271