Imidacloprid in United States Rivers, 2013-2022: Persistent Presence and Emerging Chronic Hazard.

Area of Science:

• Environmental Chemistry
• Ecotoxicology
• Aquatic Ecology

Background:

• Imidacloprid is a widely used neonicotinoid insecticide.
• It is known to be toxic to aquatic organisms, even at low concentrations.
• Its presence in U.S. waterways poses a potential risk to ecosystem health.

Purpose of the Study:

• To evaluate the detection and temporal trends of imidacloprid concentrations in U.S. rivers.
• To assess the ecological risk posed by imidacloprid contamination.

Main Methods:

• Analysis of 12,547 water samples collected from 77 U.S. rivers between 2013 and 2022.
• Statistical evaluation of imidacloprid detections and concentration trends.

Main Results:

• Imidacloprid was detected in 44% of all samples.
• Mean concentrations (24.9 ng/L) exceeded the chronic benchmark for freshwater invertebrates (10 ng/L).
• 44% of sites showed increasing imidacloprid concentration trends, with a mean increase of 10.6 ng/L over the decade.

Conclusions:

• Widespread and persistent imidacloprid contamination in U.S. waterways presents significant ecological risks.
• Increasing concentrations and exceedances of benchmarks indicate a growing threat to aquatic life.
• The total estimated loading into the Gulf of Mexico highlights the scale of the issue.