Glyphosate and other Contaminants of Concern in Water, Sediment, and Soil in the United States

Pesticides, hormones, pharmaceuticals, and other contaminants of emerging concern (CEC) are released into the environment by agriculture, industry, and other human activities. The corresponding human and environmental risk is cumulative and can include individual and community-level impacts caused by toxicity, endocrine disruption, anti-microbial resistance, behavior alteration, and other sub-lethal effects. CEC are observed both in highly modified landscapes and in remote or pristine landscapes. Herbicides that utilize glyphosate as an active ingredient are of particular concern in the United States (US) largely due to their heavy use (~100 million kilograms per year) on soybean and corn crops that are genetically modified to tolerate it. However, glyphosate is seldom included in environmental monitoring programs, due in part to technical difficulties in measuring it at concentrations relevant to environmental studies. The U.S. Geological Survey (USGS) has conducted the largest and most comprehensive assessment of the environmental occurrence of glyphosate and its primary degradation product AMPA (aminomethylphosphonic acid) in the US, summarizing the results of 3,732 environmental samples collected from 1,341 sites in 38 States between 2001 and 2010. Results indicate that glyphosate and AMPA are mobile and occur widely in the environment. Glyphosate was detected in over 50% of samples from streams and rivers, precipitation, ditches and drains, and soil and sediment; but in less than 40% of samples from soil pore-water, groundwater, and wetlands.

Other CEC such as hormones and pharmaceuticals are commonly detected in surface water and bed sediment in urban and suburban areas due to the proximity and/or intensity of their use or their association with wastewater discharges and urban runoff. However, water and sediment from urbanized or agriculturally dominated landscapes are not the only place were CEC are found.  In 2012-2013, we sampled water and sediment from 20 sites in Rocky Mountain National Park. Water samples were analyzed for 19 hormonally active compounds, 109 pharmaceutical related compounds, and 69 wastewater related compounds; and sediment samples were analyzed for 19 hormonally active compounds and 57 wastewater related compounds. In all, 54 compounds were detected in one or more water samples and 45 were detected in one or more sediment samples. Some detected compounds, such as carbaryl, 17-α-estradiol, celecoxib, and oxycodone, are attributable to direct human input, whereas others, such as camphor, estrone, 3-beta-coprostanol, and p-cresol, may have local natural sources such as wildlife or pine needles.