Agricultural produce from Katherine will be tested as part of the Defence Forces investigation into chemicals linked with firefighting foam.

A year-long Defence Force investigation is examining what effect the leaching of per- and poly-fluoroalkyl substances (PFAS) into the water table near RAAF base Tindal has had on the population and environment.

Defence spokesperson Steve Grzeskowiak said, produce watered with contaminated bore water would be tested as part of the investigation.

"When we get the results, that will inform us whether or not these chemicals do move into vegetables or eggs and at what levels."

Most of the properties to be covered in the Defence Departments initial investigation are private residential blocks, not commercial farms. Mr Grzeskowiak said commercially produced food products would not be tested without permission.

"The extent of testing will depend on what we find after the first round of testing. My understanding is that some of the commercial producers [around Katherine] have undertaken their own testing and are comfortable with the results of those tests."