Insecticides known as neonicotinoids were commonly found in Midwest rivers and streams, according to a report released Thursday by the U.S. Department of the Interior, U.S. Geological Survey (USGS).
The finding has scientists concerned for a few of reasons. The use of neonicotinoids, which are particularly popular among corn and soybean farmers, has been linked to a number of ecological issues, including honeybee die-offs. A number of European nations have placed bans or restrictions on neonicotinoids for this very reason.
“This is the first broad-scale investigation of neonicotinoid insecticides in the Midwestern United States and one of the first conducted within the United States,” the USGS states.
The use of neonicotinoids in the United States is rising dramatically, researchers warn. The USGS reports that for Iowa corn, the use of clothianidin — a neonicotinoid — nearly doubled between 2011 and 2013.
The study found concentrations of neonicotinoids in all nine of the rivers and streams surveyed in the Midwest, with maximum concentrations of clothianidin, thiamethoxam and imidacloprid (all neonicotinoid) measured at 257, 185 and 42.7 nanograms per liter, respectively.
So, what do those numbers actually mean? The USGS offers this startling clue:
One of the chemicals, imidacloprid, is known to be toxic to aquatic organisms at 10-100 nanograms per liter if the aquatic organisms are exposed to it for an extended period of time. Clothianidin and thiamethoxam behave similarly to imidacloprid, and are therefore anticipated to have similar effect levels. [emphasis added]
As the USGS continues to investigate the ecological effects of neonicotinoids on bees and other small organisms, however, there is one silver lining: The Environmental Protection Agency says these chemicals are not likely to be carcinogenic to humans.
View an overview of the USGS study, “Widespread occurrence of neonicotinoid insecticides in streams in a high corn and soybean producing region, USA,” published in the October 2014 edition of Environmental Pollution.