atrazine is an herbicide / pesticide sprayed on crops, the runoff into rivers is known to chemically castrate, as well as change the sex of male frogs.

Atrazine, one of the world’s most widely used pesticides, wreaks havoc with the sex lives of adult male frogs, emasculating three-quarters of them and turning one in 10 into females, according to a new study by University of California, Berkeley, biologists.

The 75 percent that are chemically castrated are essentially “dead” because of their inability to reproduce in the wild, reports UC Berkeley’s Tyrone B. Hayes, professor of integrative biology.

The 10 percent or more that turn from males into females – something not known to occur under natural conditions in amphibians – can successfully mate with male frogs but, because these females are genetically male, all their offspring are male.

https://news.berkeley.edu/2010/03/01/frogs/

https://www.epa.gov/ingredients-used-pesticide-products/atrazine