ANALYSIS of the state’s sewerage has revealed West Australians use about two tonnes, or $2 billion worth, of methamphetamine a year.

It has been revealed Bunbury has the highest rate of meth use in the state — with 558 doses of the drug being used per 1000 people each week.

Camera Icon Police Minister Liza Harvey. Credit: News Corp Australia

Meanwhile, wastewater testing in Perth shows about 344 doses of meth are being used every week per 1000 people.

The State Government has been testing raw sewerage since July last year, revealing the secrets of the WA’s illicit drug use.

Three catchments — Bunbury, Perth and Geraldton — were used in the trial.

Police can also use the data to show how different busts affect meth use in different communities and will be expanding the trial to the remote townships in the Kimberley in coming weeks.

Police Minister Liza Harvey said the project had, for the first time, provided science-based evidence of the scale of meth use across the WA community.

“The results provide the most accurate data yet on consumption levels; daily, weekly and seasonal rates; trends; and a broad geographical breakdown,” she said.

Testing assumes a meth purity of 68.5 per cent and doses are assumed to be a “point”, which is 0.1 gram of the drug worth $100 on the street.

The data will help inform the State Government’s WA Meth Strategy 2016, aimed at educating, providing treatment to addicts and disrupting supply.

Meth use in WA is about twice the national average, according to data from 2013, revealing about 3.8 per cent of the population used the drug.