The hormone-disrupting herbicide atrazine is contaminating nearly 25%, or about 860,000 miles, of all continental US rivers at levels that can harm wildlife and may threaten human health, a new review of federal records has found.

The waterways cover over 20% of surface drinking water intakes across the country, and over 675,000 private and commercial wells.

Atrazine can have severe impacts on human and animal hormones, especially for developing children. It was found to “chemically castrate” frogs, and cause some to change sexes. The herbicide is so dangerous that it has been effectively banned in 60 countries, including the European Union, since 2003.