Popular farm pesticides found in drinking water

Occurrence of Neonicotinoid Insecticides in Finished Drinking Water and Fate during Drinking Water Treatment

A team of chemists and engineers at the U.S. Geological Survey and University of Iowa reported that they found neonicotinoids in treated drinking water. It marks the first time that anyone has identified this class of pesticide in tap water.

2017 Study Abstract

Neonicotinoid insecticides are widespread in surface waters across the agriculturally intensive Midwestern United States.

We report for the first time the presence of three neonicotinoids in finished drinking water and demonstrate their general persistence during conventional water treatment.

Occurrence of Neonicotinoid Insecticides in Finished Drinking Water and Fate during Drinking Water Treatment,
American Chemical Society, April 5, 2017.

Periodic tap water grab samples were collected at the University of Iowa over 7 weeks in 2016 (May–July) after maize/soy planting.

Clothianidin, imidacloprid, and thiamethoxam were ubiquitously detected in finished water samples at concentrations ranging from 0.24 to 57.3 ng/L.

Samples collected along the University of Iowa treatment train indicate no apparent removal of clothianidin or imidacloprid, with modest thiamethoxam removal (∼50%).

First evidence found of popular farm pesticides in drinking water, washingtonpost, April 5, 2017.

Image credit ℒaura Tou.

In contrast, the concentrations of all neonicotinoids were substantially lower in the Iowa City treatment facility finished water using granular activated carbon (GAC) filtration.

Batch experiments investigated potential losses. Thiamethoxam losses are due to base-catalyzed hydrolysis under high-pH conditions during lime softening.

GAC rapidly and nearly completely removed all three neonicotinoids. Clothianidin is susceptible to reaction with free chlorine and may undergo at least partial transformation during chlorination.

Our work provides new insights into the persistence of neonicotinoids and their potential for transformation during water treatment and distribution, while also identifying GAC as a potentially effective management tool for decreasing neonicotinoid concentrations in finished drinking water.

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