A widely used herbicide can interfere with animals’ sexual development, according to a growing body of research. Applied to agricultural fields, residential lawns, and elsewhere to kill weeds, atrazine is often found in low levels in streams, lakes, and drinking water in the U.S. and Australia, the world’s two biggest users.

A study published in August in the journal Reproduction, Fertility and Development found that atrazine impaired genital development of tammar wallabies, an Australian marsupial in the same family as kangaroos. When researchers gave female wallabies drinking water with the herbicide throughout their pregnancy and while nursing, their male offspring developed shorter, smaller penises.

The research provides more evidence that atrazine “messes around with the way that our hormones are