A new study has added to mounting evidence against a class of insecticides called neonicotinoids, or "neonics."

Linked in numerous studies to bee declines, the new research looks at neonics' impacts on surface water.

Researchers with the U.S. Geological Survey looked at 9 rivers and streams in the U.S. Midwest—home to vast plantings of corn and soybeans as well as widespread use of neonics—in the 2013 growing season.

The researchers detected neonics in all the waterways, which included the Mississippi and Missouri Rivers. One systemic pesticide, clothianidin, was found in 75 percent of the water samples.

“We noticed higher levels of these insecticides after rain storms during crop planting, which is similar to the spring flushing of herbicides that has been documented in Midwestern U.S. rivers and streams,” USGS scientist Michelle Hladick, the report’s lead author, said in a statement.

“In fact, the insecticides also were detected prior to their first use during the growing season, which indicates that they can persist from applications in prior years,” Hladick stated.

"Concentrations may frequently exceed chronic aquatic toxicity values during growing season," the study states.

"The fact that neonics are pervasively contaminating surface waters should be a wake-up call for state and federal regulators."

—Emily Marquez, Pesticide Action Network"Given the widespread use of neonicotinoid pesticides, their persistence in soil, and their high solubility in water, it's not surprising that neonics are ending up in Midwest waterways," said Emily Marquez, PhD, staff scientist at Pesticide Action Network.

"Researchers have recently documented the frequent detection of neonics at varying concentrations in surface waters in the U.S. and Canada," she continued. "The fact that neonics are pervasively contaminating surface waters should be a wake-up call for state and federal regulators, that must move more quickly to reduce and restrict use on farm fields."

The findings of the study, which the USGS touts as the first broad-scale investigation of neonics in the Midwest, were published in Environmental Pollution.

The USGS study comes on the heels of findings by researchers from the Netherlands who noted that concentrations of one neonic called imidacloprid were linked to declines in bird population, suggesting "the impact of neonicotinoids on the natural environment is even more substantial than has recently been reported."

And a global analysis out last month based on 800 peer-reviewed reports found "clear evidence" that neonics pose threats to bees, other pollinators and terrestrial invertebrates like earthworms, which are exposed to neonics through the soil, the treated plant itself and water.

"The global scientific community points to neonics as critical driver of bee declines. Officials should take water contamination as yet another sign that we must act now," Marquez stated.