Zoom in and click on points to see location-specific data documenting the detection of microcystins in public lakes from 2007, 2012 and 2018. The approximate locations represent an average of all microcystin detections. Only locations with an average above zero are displayed. Larger points indicate an average microcystin detection above 4 micrograms per liter, or µg/L, the EPA’s recommended recreational advisory. After EWG completed its survey, the EPA revised its recreational or swimming advisory in May of 2019, doubling the recommended swimming advisory to 8 µg/L. EWG derived results from publicly available records from the Environmental Protection Agency; National Oceanic and Atmospheric Administration; and the states of California, Florida, Iowa, Kansas, Nebraska, Ohio, Oregon and Wyoming. We requested and received data from Indiana, Illinois, New York, North Carolina and Virginia.
Small dots: less than 4 µg/L
Large dots: 4 µg/L and above