World Wildlife Fund Canada said its new maps tracking chloride from road salt show levels in many rural and urban southern Ontario waterways are increasing dangerously.

Salt's chloride component is toxic to freshwater species and ecosystems, compromising habitats for fish, frogs, mussels and other creatures, and endangering their survival during the spring and summer spawning season, the organization said.

"Basically it's lethal levels of salt we're seeing," said Elizabeth Hendriks, WWF Canada's vice-president of freshwater.