The fallout from a controversial Californian court decision which found the commonly used herbicide Roundup causes cancer, is now being felt in Australia.

Hundreds of users of Roundup here are preparing legal cases against chemical giant Monsanto, the manufacturer of the weed killer. Their cases add to the already 17,000 cases launched in the United States.

This Sunday on 60 Minutes, reporter Liam Bartlett investigates the claim Roundup is unsafe and life-threatening.

In his first Australian media interview, Lee Johnson the Californian cancer sufferer who was the first to take legal action against Monsanto tells Bartlett he was required to regularly use Roundup while working as a school groundsman. 

Johnson says despite always using the chemical carefully and following the instructions on the packaging, in 2014 he was diagnosed with incurable non-Hodgkins Lymphoma.

In August last year, a jury determined exposure to the chemical had caused Johnson’s cancer and awarded him US$289 million compensation, later reduced to $78 million.