Hazard Assessment Of Carbofuran On Aquatic Organisms In The Sacramento River System.pdf

It focuses on protecting sensitive species from pesticide runoff entering the estuary during the May-June discharge period.

Key Findings:

Acute Toxicity: The most sensitive species tested was the dungeness crab (Cancer magister) with a 96-hour EC50 value of 1.5 µg/L. Due to insufficient data for other species, an interim Acute Fatal Value (FAV) equal to this value was proposed.
Chronic Toxicity: Reliable data were lacking for calculating a Final Chronic Value (FCV). A chronic study with the cladoceran Ceriodaphnia dubia lacked measured exposure levels, and a study with dungeness crab used widely separated exposure levels. An interim FCV equal to a 28-day No Observable Effect Concentration (NOEC) of 0.4 µg/L for mysidopsis bahia was proposed due to imprecise values.
Interim Water Quality Criterion: Based on the available data, an interim Water Quality Criterion (WQC) of 0.5 µg/L carbofuran is recommended to protect sensitive aquatic organisms in the Sacramento River system.
Additive Toxicity: Carbofuran exhibits additive toxicity with other commonly used rice insecticides, malathion and methyl parathion. This necessitates further study to refine WQC levels considering combined effects.
Historical Concentrations: Maximum carbofuran concentrations in agricultural drains have declined significantly since 1987, indicating reduced risk to aquatic invertebrates. However, past concentrations exceeded the proposed WQC in some years.

Recommendations:

The report recommends:

Conducting additional acute toxicity tests with insects and amphipods to calculate a more precise FAV.
Repeating the chronic test with Ceriodaphnia dubia using measured exposure levels.
Completing a chronic test with Neomysis mercedis, given their sensitivity to carbofuran and importance in the estuary ecosystem.