Surface water from streams across the United States contain a diverse mixture of synthetic organic pollutants, according to a joint U.S. Geological Survey (USGS) and U.S. Environmental Protection Agency (EPA) study reported in the journal Environmental Science & Technology (April 2017). Thirty-four streams in urban and agricultural locations and four streams in remote locations were sampled and tested for the presence of 719 organic (target) compounds. Of the target compounds, 406 (about 56 percent) were detected at least once, with contaminant mixtures ranging from four to 161 chemicals per stream (median of 70 chemicals per stream). See also: River; Water conservation; Water pollution
The most frequently detected pollutants in the study were antibacterials, pharmaceuticals, and pesticides, as well as their metabolites and degradation products at concentrations ranging from nanograms per liter to micrograms per liter. All of these are bioactive chemicals that tend to resist biodegradation. Most water treatment plants are not designed to remove such low levels of pollutants. See also: Pesticide; Pharmaceutical residues in the environment; Removing organic micropollutants from wastewater; Sewage treatment
To put these results in perspective, the 719 target compounds represent about one percent of the estimated 80,000 synthetic organic compounds in use. Consequently, the actual number and cumulative concentration of pollutants in streams is potentially much higher. Fish and other wildlife are exposed to these chemicals, while humans risk exposure through drinking water and consuming contaminated wildlife. According to the researchers, the study's findings are of concern because it is not well understood how mixtures of bioactive contaminants affect human and ecological health. See also: Environmental toxicology; Freshwater ecosystem; Toxicology