Environmental concentrations and aquatic toxicity data on diflubenzuron (dimilin)

Area of Science:

• Environmental Toxicology
• Ecotoxicology
• Insecticide Fate and Transport

Background:

• Diflubenzuron (DFB) is widely used for gypsy moth suppression in mid-Atlantic hardwood forests.
• DFB can enter aquatic systems via aerial drift or runoff, posing risks to non-target organisms.
• Understanding DFB's environmental behavior and toxicity is crucial for ecological risk assessment.

Purpose of the Study:

• To synthesize existing literature on DFB's fate, persistence, and environmental concentrations in aquatic environments.
• To compile and review aquatic toxicity data for DFB on freshwater and saltwater organisms.
• To assess the potential risks of DFB to aquatic biota in Maryland and identify research gaps.

Main Methods:

• Comprehensive literature review and synthesis of DFB's environmental fate and persistence.
• Compilation and review of acute and chronic toxicity data for aquatic organisms.
• Risk assessment for aquatic ecosystems in a specific region (Maryland).

Main Results:

• DFB exhibits low water solubility; its toxicity is similar for technical grade and wettable powder formulations below 10 µg/L.
• Organic matter significantly influences DFB adsorption and degradation; persistence varies with pH and temperature (e.g., half-life of ~3 days at pH 10, 36°C vs. ~9 days at pH 6).
• Aquatic invertebrates are highly sensitive to DFB, with acute LC50 values significantly lower than for fish; chronic exposure can eliminate sensitive invertebrate populations (e.g., stoneflies, mayflies).

Conclusions:

• DFB's persistence and degradation are influenced by environmental factors like pH, temperature, and organic matter.
• Aquatic invertebrates, particularly those with exoskeletons, are highly vulnerable to DFB toxicity across different life stages.
• DFB poses a significant risk to aquatic ecosystems, necessitating further research to refine risk assessments and inform management strategies.