Third-generation Melbourne market gardener David Wallace is one of dozens of landholders who have been told to stop using water from the Maribyrnong River after toxic chemicals from firefighting foam were detected in runoff from Melbourne Airport.

Mr Wallace's family has been farming in the Keilor Valley, 15 kilometres north of Melbourne, for 113 years. He spends around $5000 a year on a diversionary licence from Melbourne Water, giving him access to water from the Maribyrnong River.

David Wallace's property, which has been in his family for 113 years, borders the Maribyrnong River. Credit:Jason South

Now he has been told to stop, after an EPA alert was issued on September 20, following tests for per- and poly-fluoroalkyl chemicals – known as PFAS – at Melbourne Airport and in nearby waterways.

The Department of Health maintains there is no consistent evidence the toxins cause “important” health effects, in contrast to the US EPA, which has concluded they are a human health hazard that – at high-enough levels – can cause immune dysfunction, hormonal interference and certain types of cancer.