The unedited response follows:

Katherine Town Water Supply and PFAS Testing Results

Last year, the Australian Department of Defence notified the NT Government of the presence of PFAS at some Defence bases – including Tindal

Results for the testing of PFAS in the Katherine town water supply are published online at: www.powerwater.com.au/networks_and_infrastructure/water_services/pfas

Power and Water conducts water testing on a weekly basis at a number of sites within the Katherine public water supply system. These are published as a rolling monthly average and show the levels of PFAS in the water supply remain below the Health Based Guideline Values (HBGV).

Four tests have exceeded the Health Based Guidance Values since testing began in November 2016 and these fluctuations will likely continue.

The Federal Chief Medical Officer and Northern Territory Chief Health Officer have confirmed the water is safe to drink as the PFAS HBGV is a ‘whole of life’ consumption measure with a safety factor of 30 built into it.

Last year, the Australian Department of Defence notified the Northern Territory Government of the presence of per-and poly-fluoroalkyl substances, also known as 'PFAS', in the vicinity of some Defence bases around Australia including Tindal.

PFAS are a group of manufactured chemicals that have been used since the 1950s in a range of common household products and specialty applications, including in the manufacture of non-stick cookware; fabric, furniture and carpet stain protection applications; food packaging; some industrial processes; and in some types of fire-fighting foams.

Whether PFAS has an effect on human health is not clear.  Exercising appropriate caution, Australian Health Based Guidance Values for PFAS were developed (and endorsed by the Commonwealth Department of Health) to indicate the amount of the PFAS chemical in drinking water supplies that a person can consume on a regular basis over a lifetime without any significant risk to health.

These Health Based Guidance Values (HBGV) include a drinking water guideline and now used by Power Water Corporation (PWC) for monitoring levels of PFAS in drinking water supplies in the NT, via an extensive water sampling program.

The types of PFAS chemicals tested for are known as PFOS, PFHxS and PFOA. The HBGV for drinking water is 0.07µg /L (PFOS + PFHxS) and 0.56 µg /L (PFOA).  These levels include a safety factor of 30, which means that the measured PFAS levels in drinking water would have to significantly exceed these readings over a prolonged period for there to be any risk from exposure.

At the request of the Department of Health, PWC conducts water testing on a weekly basis at a number of sites within the Katherine public water supply system as a response to the detection of PFAS in bores near the Tindal RAAF base.

Sampling results are reported as a rolling average, and taking into account the results from the most recent samples, the PFAS level in the drinking water remains below the HBGV of 0.07µg/L.

It would not be surprising for individual sample results to move slightly from one sample to the next, and this has been the case, with some recent samples slightly exceeding the HBGV of PFAS (PFOS+PFHxS).  However the most recent results of sampling undertaken by PWC have revealed levels of PFAS below the HBGV, and this is also the longer-term rolling average result.

The Commonwealth Deputy Chief Medical Officer, Dr Tony Hobbs has advised that there is minimal risk to human health posed by short term exceedances of the HBGV for drinking water, particularly where there is limited intake of PFAS from other sources and the long term average is below the HBGV.

This advice is supported by the Northern Territory Chief Health Officer, Dr Hugh Heggie, who has reiterated that the PFAS HBGVs are a measure of whole-of-life exposure (that is, spanning many decades), not shorter-term exposure. Dr Heggie has also underscored that there is no consistent evidence of any link between PFAS and human health impact.

The Katherine public water supply is considered by the experts to be safe to drink, and consumers of the Katherine water supply are not required to take any action in relation to their water supply. 

The results of water testing are ongoing and the Chief Health Officer will update this advice as appropriate.

A government spokeswoman also added that the 0.07 PFAS limit is an average and that average is currently at 0.05 and has remained below the 0.07 limit - even though four individual  tests have been above this level.