Insecticide Risk in US Surface Waters: Drivers and Spatiotemporal Modeling

Area of Science:

• Environmental Chemistry
• Ecotoxicology
• Water Quality Assessment

Background:

• Pesticide contamination in agricultural surface waters is widespread.
• Large-scale studies identifying drivers of insecticide risk are scarce.

Purpose of the Study:

• To identify key drivers of insecticide risks in US surface waters.
• To map national-scale risks to aquatic organisms based on regulatory threshold levels (RTLs).

Main Methods:

• Analysis of 5830 insecticide and metabolite concentrations from 259 publications across 644 US surface waters.
• Multiple linear regression to identify risk drivers.
• Development and validation of a national-scale risk mapping model.

Main Results:

• Toxicity-normalized agricultural insecticide use was the primary driver of risk.
• Burst rainfall erosivity and irrigation practices increased risk; time, catchment size, and sampling interval decreased risk.
• Smaller streams exhibited the highest risk, with 27.7% average RTL exceedance frequency.

Conclusions:

• Insecticide risks in surface waters are driven by agricultural practices and environmental factors.
• National risk mapping highlights areas with adverse conditions for aquatic life.
• Understanding drivers and mapping risks supports effective water resource management and mitigation strategies.