April 5 (UPI) -- For the first time, researchers have detected traces of neonicotinoids, a common class of pesticides, in tap water.
Scientists have previously identified neonicotinoid contamination in rivers and streams, but the latest report -- published in the journal Environmental Science & Technology Letters -- shows the potent chemicals are making their way into some drinking water sources.
Researchers from the University of Iowa and the U.S. Geological Survey measured between 0.24 and 57.3 nanograms of individual neonicotinoids per liter of water in samples collected from a water system serving Iowa City. The rapid sand filtration system used by the University of Iowa removed just 1 percent of the pesticides. Iowa City's cleaning system, granular activated carbon filtration, removed nearly all of the insecticides from the samples.
Currently, there are no federal limits for the amount of neonicotinoids allowed in drinking water. Scientists are still studying the effects of the chemicals on human health.
"These are very low levels, these are nanograms per liter, which means parts per trillion, a very low concentration," Gregory LeFevre, a researcher at the University of Iowa, told BBC News. "But at the same time there are concerns about what those low levels might do from an exposure standpoint."
Several studies have shown the insecticides to be harmful to honey bees, and some research has shown the chemicals are damaging to the health of other animals.
There is also concern that some filtration processes could transform neonicotinoids into more harmful compounds. Scientists suggest more research is needed to gauge the risk of neonicotinoid contamination to human health.