The New South Wales Opposition is demanding answers after testing on a river in the New South Wales Central West showed extensive levels of P-FAS chemicals.

Samples of foam taken from the Belubula River showed more than 18-hundred times the safe limit for a drinking source.

The chemicals are linked to cancer, hormone and immune issues and developmental problems in children.

Rural Editor Emily Minney has spoken with Shadow Water Minister Steph Cooke about the contamination.