dead zone

Abbie Fentress Swanson/Harvest Public Media

This spring and summer, U.S. Geological Survey scientists waded into 100 Midwest streams to test for hundreds of chemicals used in farming, including nutrients, pesticides like atrazine and glyphosate, and livestock hormones. The results from the study are trickling in. But preliminary findings indicate that from May through early July, 21 percent of the region’s streams contained very high levels of nitrogen in the form of nitrates.