| Abstrakt: |
Fathead minnows, 30 days old, were exposed to technical grade bromacil and diuron in flow-through tests to determine acute toxicity. LC50 values for bromacil were 185, 183, 182 and 167 mg/L at 24, 48, 96, and 168 hr, respectively; and for diuron, 23.3, 19.9, 14.2, and 7.7 mg/L at 24, 48, 96, and 192 hr, respectively. Eggs, newly hatched fry, and juvenile fish were continuously exposed to lower concentrations of the herbicides for 64 days. Growth was significantly reduced (p ? 0.01) at the lowest bromacil exposure of 1.0 mg/L. Therefore, it was not possible to determine a “no effect” concentration. The “no effect” concentration for diuron was 33.4 µg/L, while the lowest concentration which resulted in adverse effects was 78.0 µg/L. Adverse effects at 78.0 µg/L were an increased incidence of abnormal or dead fry immediately after hatch (p ? 0.01) and decreased survival throughout the exposure period (p ? 0.05). Neither herbicide accumulated significantly in fish tissue, as bioconcentration factors were <3.2 and 2.0 for bromacil and diuron, respectively. Rainbow trout (Salmo gairdneri) injected with radiolabeled bromacil or diuron eliminated over 90% of the radioactivity within 24 hr. Parent compound and metabolites were detected in the aquarium water in both cases. Metabolites of diuron recovered from the water included 3,4-dichloroaniline and several demethylated products. |
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