Skip to main content
U.S. flag

An official website of the United States government

Inclusion of pesticide transformation products is key to estimating pesticide exposures and effects in small U.S. streams

March 10, 2021

Improved analytical methods can quantify hundreds of pesticide transformation products (TPs), but understanding of TP occurrence and potential toxicity in aquatic ecosystems remains limited. We quantified 108 parent pesticides and 116 TPs in more than 3 700 samples from 442 small streams in mostly urban basins across five major regions of the United States. TPs were detected nearly as frequently as parents (90 and 95% of streams, respectively); 102 TPs were detected at least once and 28 were detected in >20% samples in at least one region—TPs of 9 herbicides, 2 fungicides (chlorothalonil and thiophanate-methyl), and 1 insecticide (fipronil) were the most frequently detected. TPs occurred commonly during baseflow conditions, indicating chronic environmental TP exposures to aquatic organisms and the likely importance of groundwater as a TP source. Hazard quotients based on acute aquatic-life benchmarks for invertebrates and nonvascular plants and vertebrate-centric molecular endpoints (sublethal effects) quantify the range of the potential contribution of TPs to environmental risk and highlight several TP exposure–response data gaps. A precautionary approach using equimolar substitution of parent benchmarks or endpoints for missing TP benchmarks indicates that potential aquatic effects of pesticide TPs could be underestimated by an order of magnitude or more.

Citation Information

Publication Year 2021
Title Inclusion of pesticide transformation products is key to estimating pesticide exposures and effects in small U.S. streams
DOI 10.1021/acs.est.0c06625
Authors Barbara Mahler, Lisa H. Nowell, Mark W. Sandstrom, Paul Bradley, Kristin Romanok, Christopher Konrad, Peter Van Metre
Publication Type Article
Publication Subtype Journal Article
Series Title Environmental Science and Technology
Index ID 70219076
Record Source USGS Publications Warehouse
USGS Organization California Water Science Center; National Water Quality Laboratory; New Jersey Water Science Center; Washington Water Science Center; South Atlantic Water Science Center; Oklahoma-Texas Water Science Center