Further testing will take up to 10 weeks | Image: Mattinbgn, CC BY 3.0, via Wikimedia Commons.
An investigation has been launched after drinking water from Merriwa exceeded the advised radioactivity levels.
Routine tests were conducted on samples taken from the Merriwa water supply groundwater bores and identified radiation levels above the screening values set out in the Australian Drinking Water Guidelines (ADWG).
The guidelines use a reference level of 1 milliSievert per year and initial assessments of the water samples taken show the current figure is roughly double that.
Upper Hunter Shire Council is now working with NSW Health and the Department of Climate Change, Energy, the Environment and Water to ensure the ongoing safety of the Merriwa drinking water supply.
In a statement, the council said it does not mean the town’s drinking water is unsafe, but that further investigation is required.
“NSW Health advises that the level of radiation is unlikely to pose a health risk,” the statement said.
“NSW Health have assessed the maximum possible dose based on the current screen level results to be approximately 2mSv/year… Standard medical diagnostic equipment such as CT scans can deliver a dose as high as 10mSv. However, efforts should be made to reduce exposure where feasible if the annual radiation dose in drinking water is found to exceed 1mSv.”
“The dose of radiation will be accurately calculated when the radionuclides in the water have been measured.”
That process is expected to take up to 10 weeks as experts from the Australian Nuclear Science and Technology Organisation (ANSTO) are brought in to conduct detailed testing.
In the meantime, the Shire council has switched to using two bores with the lowest radioactivity as a precaution.
The time consuming process requires the activity of each radioactive material, known as a radionuclide, in the water to be separately measured. It is a complicated task, as the radiation detected could originate from various materials found within the water source and each is likely to give a different dose of radiation.
The type or radionuclides at work in Merriwa have been identified as Alpha and Beta particles, which are from natural sources such as underground rock material that is in contact with the water.
“Radioactive materials occur naturally in the environment and everyone is exposed to low levels of radiation. Some minerals that emit radiation can be present in drinking water and typically contribute a small amount to overall exposure to naturally occurring radiation,” the council statement said.
“Naturally occurring radiation is more likely to be found in bore water.”
Once ANSTO’s final testing results are received, the council will begin planning the next steps in consultation with key stakeholders including NSW Health and the Department of Climate Change, Energy, the Environment and Water.
The community will be kept informed of all developments via official channels. More information can be found HERE.