Sydneysiders consume more than twice as much cocaine than other areas, an examination of wastewater treatment plants across Australia finds.

Sydneysiders are consuming more than twice as much cocaine as people in Melbourne and Brisbane, according to Australia's sewers.

In August last year, for every 1000 people, 1.2 grams of cocaine was consumed daily in Sydney, compared with just over 400 milligrams in Melbourne and Brisbane.

The figures were revealed in the Australian Criminal Intelligence Commission's most recent examination of wastewater treatment plants across the country, compiled in partnership with the University of Queensland and University of South Australia.

NSW POLICE FORCE Australia's demand for illicit substances has not gone unnoticed by international drug dealers. Border Force officials at Sydney Airport seized 154kg of heroin blocks which were allegedly hidden in crates containing straw hats and souvenir items.

It is the sixth report of the National Wastewater Drug Monitoring Program, which covers 56 per cent of Australia's population, or 13 million people, and is concluding its second year.

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It found that capital city and regional locations in New South Wales in August last year were the only parts of Australia where cocaine consumption rivalled levels of methylamphetamine, or ice.

Everywhere else, cocaine use was detected to be far below that of methylamphetamine.

Nationally, more than 4.1 tonnes of cocaine was consumed between 2017 and 2018, an increase of 34.6 per cent on the previous year, worth A$1.5 billion ($1.56b).

Between August 2017 and August 2018, the study found A$9.3 billion ($9.7b) was spent on almost 10 tonnes of methylamphetamine, more than four tonnes of cocaine, 1.1 tonne of MDMA and 700kg of heroin.

Of the A$9.3 billion, almost 80 per cent was spent on methylamphetamine.

The dollar figure is not far off the A$9.8 billion Australians are estimated to spend at cafes and coffee shops in a single year, according to a recent IBIS World Australia Industry Report.

Over two years the study collected samples of 13 different substances, including alcohol, nicotine, oxycodone, heroin and MDMA (or ecstasy) from 58 wastewater treatment plants.

In NSW, data was collected from five wastewater plants in Sydney and seven from regional sites.

Each site was allocated a code, to maintain the confidentiality of participating sites.

The demand for illicit substances has not gone unnoticed by international drug dealers, with an estimated A$1.29 billion worth of methylamphetamine bound for Australia seized earlier this month in the United States, just weeks after 154kg of heroin worth around A$77 million was seized by Border Force officials at Sydney Airport.

"It is astounding that Australians waste over A$9.3 billion a year on drugs," ACIC chief executive officer Michael Phelan said.

"This is money people could be spending on legitimate goods for themselves and their families."

For the first time the report also recorded levels of cannabis consumption, which Phelan described as "one of the most used illicit drugs, both domestically and internationally".

According to the report, consumption of cannabis, an illicit depressant, was reportedly low in NSW compared to the rest of Australia, with Tasmania recording the highest levels of use overall.

However, as the specific marker for cannabis consumption is excreted in extremely small amounts, the report's authors identified possible "spatial differences...across the nation".

The drug consumption figures come at the end of a period that saw five drug-related deaths at music festivals, which prompted controversial debate about the merits of pill-testing and the dangers of party drugs like MDMA, or ecstasy.

Yet in comparisons of wastewater from August 2016 to August 2018, the population-weighted average consumption of MDMA in capital city and regional sites around Australia decreased. The same was true for levels of oxycodone detected at wastewater sites.

Consumption of methylamphetamine, cocaine, fentanyl, nicotine and alcohol in the same period increased. Of the 13 substances surveyed, alcohol and nicotine were the most highly consumed of those measures with available dose data.

In regional areas, consumption of alcohol, nicotine, methylamphetamine, MDMA, MDA, oxycodone, fentanyl and cannabis surpassed levels recorded in capital cities.

