A federal study published in the journal Environmental Science and Technology shows smaller amounts of a common bug killer may be more harmful in Midwest streams than previously thought.

The chemical compound bifenthrin is used to kill mosquitoes, aphids on crops, and ants and termites in households. But the insecticide also gets into waterways.

The U.S. Geological Survey has looked at the presence of bifenthrin in some streams, including some in eastern Wisconsin.

Smaller amounts of bifenthrin are harming tiny bugs that help eat algae, said USGS research ecologist Travis Schmidt.

“In this case, an insecticide affected aquatic insects and that in turn made the algae community increase,” Schmidt said.

Too much algae can affect water quality, he said, and bifenthrin also appears to be affecting the life cycle of other beneficial insects like mayflies and midges.

“It absolutely was killing the larvae, and it was having affects also on the adult life stages, their ability to complete metamorphosis and emerge from the stream,” Schmidt said.