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Study Highlights the Complexity of Chemical Mixtures in United States Streams

USGS scientist collecting water-quality samples from the Enoree River, SC
U.S. Geological Survey (USGS) scientist collecting water-quality samples from the Enoree River, South Carolina (USGS Site ID: 02160326). The samples were assessed for more than 700 organic chemicals as well as indicators of biological effects. Photo Credit: Celeste A. Journey, USGS.

A new study highlights the complexity of chemical mixtures in streams and advances the understanding of wildlife and human exposure to complex chemical mixtures.

Chemical contaminants do not occur alone in our water resources and detections of complex chemical mixtures are commonly documented in rivers and streams across the United States. Fish and other wildlife are exposed to these complex mixtures of chemicals. There is also the potential for human exposure through direct skin absorption, ingestion of contaminated drinking water, or consumption of contaminated wildlife.

This study builds on previous work that identified mixtures of contaminants in streams across the United States. The U.S. Geological Survey (USGS) and the U.S. Environmental Protection Agency (EPA) collaborated to assess more than 700 organic chemicals as well as indicators of biological effects in 38 streams within the United States, which represented one of the most comprehensive set of contaminants ever monitored at individual stream sites. This study was an opportunity to assess the factors related to site-to-site differences in stream-contaminant complexity and to put the chemical data into context with potential effects on aquatic animal health.

USGS scientist processing water quality samples. She is surrounded by lots of equipment
USGS scientist processing water quality samples collected from the Enoree River, South Carolina (USGS Site ID: 02160326). Logistics were big part of the study. Photo Credit: Paul M. Bradley, USGS.

The results indicate that the mixtures of chemicals in streams reflect combined contaminant contributions originating from a combination of agricultural, industrial, municipal, and residential sources in individual watersheds. Complex chemical mixtures (a range of 4 to 161 chemicals per stream) were detected in streams across a range of urban and agricultural areas in the United States. As expected, fewer chemicals were detected in the 4 streams that had low population density compared to the 34 urban/agricultural-influenced locations.

Indicators of biological activity, such as estrogen receptor activation, were present in all stream samples except for one reference site. Estrogenicity activity values have yet to be firmly established; however, multiple sites exceeded activity levels estimated to signal potential adverse effects on aquatic organisms. The indicators were related to target chemicals in the water samples to different degrees, which advanced our understanding of exposure and relative risk of specific chemicals and mixtures.

The results of this overall effort yield insights into the complexity of chemical mixtures present in a wide range of surface waters across the United States and their potential for eliciting adverse ecological health consequences. These results are important to answer questions about minimizing health risks and economic costs, if any, associated with mixed-contaminant exposures.

The USGS Toxic Substances Hydrology Program, the EPA Safe and Sustainable Water Resources, and the Chemical Safety for Sustainability Research Programs funded this study.

References

Bradley, P.M., Journey, C.A., Romanok, K.M., Barber, L.B., Buxton, H.T., Foreman, W.T., Furlong, E.T., Hladik, M.L., Glassmeyer, S.T., Iwanowicz, L.R., Jones, D.K., Kolpin, K.W., Kuivila, K.M., Loftin, K.A., Mills, M.A., Meyer, M.T., Orlando, J.L., Reilly, T.J., Smalling, K.L., and Villeneuve, D.L., 2017, Expanded target-chemical analysis reveals extensive mixed-organic-contaminant exposure in USA streams: Environmental Science and Technology, https://dx.doi.org/10.1021/acs.est.7b00012.

Conley, J.M., Evans, N., Cardon, M.C., Rosenblum, L., Iwanowicz, L.R., Hartig, P.C., Schenck, K.M., Bradley, P.M., and Wilson, V.S., 2017, Occurrence and in vitro bioactivity of estrogen, androgen, and glucocorticoid compounds in a nationwide screen of United States stream waters: Environmental Science and Technology, https://dx.doi.org/10.1021/acs.est.6b06515.

Romanok, K.M., Reilly, T.J., Barber, L., Boone, Scott, Buxton, H.T., Foreman, W.T., Furlong, E.T., Hladik, M., Iwanowicz, L.R., Journey, C., Kolpin, D.W., Kuivila, K., Loftin, K.A., Mills, M.A., Meyer, M.T., Orlando, J.L., Smalling, K.L., Villeneuve, D.L., and Bradley, P.M., 2017, Methods used to characterize the chemical composition and biological activity of environmental waters throughout the United States, 2012–14: U.S. Geological Survey Open-File Report 2017–1011, 105 p., https://doi.org/10.3133/ofr20171011.

Bradley, P.M., Journey, C.A., Romanok, K.M., and Reilly, T.J., 2017, Targeted-organic-chemical analysis concentration data for surface-water samples collected from 38 stream sites across the USA during 2012-2014: U.S. Geological Survey Data Release, https://doi.org/10.5066/F70863G5.

Romanok, K.M., Bradley, P.M., and Journey, C.A., 2017, Inorganic and organic concentration data collected from 38 streams in the United States, 2012-2014, with supporting data, as part of the Chemical Mixtures and Environmental Effects Pilot Study: U.S. Geological Survey Data Release, https://doi.org/10.5066/F7GF0RPH.

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