Expanded Target-Chemical Analysis Reveals Extensive Mixed-Organic-Contaminant Exposure in U.S. Streams

Surface water from
38 streams nationwide was assessed using 14
target-organic methods (719 compounds). Designed-bioactive anthropogenic
contaminants (biocides, pharmaceuticals) comprised 57% of 406 organics
detected at least once. The 10 most-frequently detected anthropogenic-organics
included eight pesticides (desulfinylfipronil, AMPA, chlorpyrifos,
dieldrin, metolachlor, atrazine, CIAT, glyphosate) and two pharmaceuticals
(caffeine, metformin) with detection frequencies ranging 66–84%
of all sites. Detected contaminant concentrations varied from less
than 1 ng L–1 to greater than 10 μg L–1, with 77 and 278 having median detected concentrations
greater than 100 ng L–1 and 10 ng L–1, respectively. Cumulative detections and concentrations ranged 4–161
compounds (median 70) and 8.5–102 847 ng L–1, respectively, and correlated significantly with wastewater discharge,
watershed development, and toxic release inventory metrics. Log10 concentrations of widely monitored HHCB, triclosan, and
carbamazepine explained 71–82% of the variability in the total
number of compounds detected (linear regression; p-values: < 0.001–0.012), providing a statistical inference
tool for unmonitored contaminants. Due to multiple modes of action,
high bioactivity, biorecalcitrance, and direct environment application
(pesticides), designed-bioactive organics (median 41 per site at μg
L–1 cumulative concentrations) in developed watersheds
present aquatic health concerns, given their acknowledged potential
for sublethal effects to sensitive species and lifecycle stages at
low ng L–1.