Secret tests of wastewater around Australia show methylamphetamine is the most popular illicit drug, with levels of use in WA far outstripping the rest of the nation.
The wastewater monitoring by the Australian Criminal Intelligence Commission, the first of nine planned tests over the next three years, confirmed anecdotal evidence that ice is the most widely used illegal drug in Australia.
The results also reinforce the outcomes of WA government tests last year, which showed the state was in the grip of an alarming meth epidemic.
While the WA monitoring of six catchment areas revealed the South West town of Bunbury was the state's meth capital, such specific information won't be made publicly available for the national study, which tested 51 sites, ACIC chief executive Chris Dawson said.
The detail from the WA tests was released under the Freedom of Information Act, he said, but the classified Australia-wide information would only be made available to police and health authorities in hotspots.
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"There's a contractual arrangement with the wastewater authorities - they did not want these sites particularly identified," he told reporters in Perth on Sunday.
Mr Dawson said the ACIC hadn't been able to sample all regional centres, so it didn't want to single out certain areas as being particularly troublesome.
"We're sensitive to that issue.
"We will review over the next three years whether we will continue in specific sites or whether the trend data invites us to actually expand."
The monitoring, which covers about 58 per cent of the population, also showed oxycodone and fentanyl use across all jurisdictions was at concerning levels.
Regional areas in Victoria and Queensland showed higher than average oxycodone levels, while fentanyl use in regional areas in NSW, South Australia and WA were above average.
"Whether that is all prescription dispensing or whether it is being diverted to an illicit market, that's the sort of information that will help us in our border protection, it will help us in our local policing," Mr Dawson said.
"It will also help the medical authorities to understand better whether there is in fact overprescribing taking place."
Mr Dawson said he had been warned by US authorities for several years that use of prescription drugs was a very significant problem there, with oxycodone users graduating to heroin.
"We take those warnings clearly on board. That's why these sorts of assessments are very important."
The monitoring also showed the use of synthetic cannabis was on the rise but ecstasy use had fallen, and NSW was Australia's cocaine hotspot.
