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Pesticides and pesticide degradates in groundwater used for public supply across the United States: Occurrence and human-health context

December 14, 2020

This is the first assessment of groundwater from public-supply wells across the United States to analyze for >100 pesticide degradates and to provide human-health context for degradates without benchmarks. Samples from 1204 wells in aquifers representing 70% of the volume pumped for drinking supply were analyzed for 109 pesticides (active ingredients) and 116 degradates. Among the 41% of wells where pesticide compounds were detected, nearly two-thirds contained compound mixtures and three-quarters contained degradates. Atrazine, hexazinone, prometon, tebuthiuron, four atrazine degradates, and one metolachlor degradate were each detected in >5% of wells. Detection frequencies were largest for aquifers with more shallow, unconfined wells producing modern-age groundwater. To screen for potential human-health concerns, benchmark quotients (BQs) were calculated by dividing concentrations by the human-health benchmark, when available. For degradates without benchmarks, estimated values (estimated benchmark quotients (BQE)) were first calculated by assuming equimolar toxicity to the most toxic parent; final analysis excluded degradates with likely overestimated toxicity. Six pesticide compounds and 1.6% of wells had concentrations approaching levels of potential concern (individual or summed BQ or BQE values >0.1), and none exceeded these levels (values >1). Therefore, although pesticide compounds occurred frequently, concentrations were low, even accounting for mixtures and degradates without benchmarks.

Citation Information

Publication Year 2021
Title Pesticides and pesticide degradates in groundwater used for public supply across the United States: Occurrence and human-health context
DOI 10.1021/acs.est.0c05793
Authors Laura M. Bexfield, Kenneth Belitz, Bruce D. Lindsey, Patricia Toccalino, Lisa H. Nowell
Publication Type Article
Publication Subtype Journal Article
Series Title Environmental Science & Technology
Index ID 70216905
Record Source USGS Publications Warehouse
USGS Organization WMA - Earth System Processes Division