The capital's annual cocaine use could be approaching a tonne if a new test is accurate, writes Claire O'Connell
A key step in tackling a problem is to know what you are up against. But when it comes to cocaine abuse, figuring out the scale of the problem in Ireland is no easy task.
That's why scientists at Dublin City University (DCU) are developing a novel approach to work out how much cocaine goes into a city - by literally measuring what comes out in the wastewater.
In the first study of its kind in Ireland, they discovered that 70 per cent of wastewater samples taken from Dublin and surrounding areas contained traces of the illicit drug. The figures also suggest that around two kilogrammes of cocaine is consumed in the greater Dublin area per day.
Assessing levels of drug use accurately is a challenge, says Prof Brett Paull, head of DCU's School of Chemical Sciences. For example, random blood testing is not an option and questionnaires are unlikely to reveal true drug-taking habits.
"Really the only non-socially invasive way you can do it to get a completely unbiased evaluation is look at waste," explains Paull. "There will always be issues with the approach - where the cocaine comes from, degradation and so forth. But there's some reasonably accurate indication of societal use from wastewater."
Paull and Dr Jonathan Bones at the National Centre for Sensor Research in DCU examined samples from wastewater plants in Ringsend, Swords, Shanganagh, Leixlip and Navan, which together serve a total of almost 2 million people in Dublin and surrounding areas.
In the lab they passed the murky wastewater samples through a special powder tailored to absorb cocaine and related compounds onto its surface. "It means you can go from a very dilute amount in a large sample to a very concentrated amount in a small sample," explains Bones, whose work is funded by the Irish Council for Science, Engineering and Technology.
Using this approach the researchers found traces of cocaine or related compounds in 70 per cent of wastewater samples taken during a weekend last November.
Thanks to the sensitivity of the test, the scientists could detect even tiny traces of drugs in the samples, says Paull. "You are talking about nanograms, or a billionth of a gram per litre."
And what comes out in the wastewater represents about 10 per cent of what people originally consumed, states Bones. "Most cocaine is transformed in the body into metabolites, but about 10 per cent passes through as cocaine, so we had to correct for the metabolism," he says.
From their calculations, the researchers estimate that around 14 doses, or 1.4g of cocaine, was consumed per 1,000 head of population for the time they conducted their tests. "That doesn't mean that on a Saturday night 14 people per thousand were taking cocaine," explains Paull. "People might take several doses in an evening."
Based on the study, which is to be published in the Journal of Environmental Monitoring, the scientists reckon that around two kilogrammes of cocaine is used in the greater Dublin area per day.
This relates to the 1.7 million people whose wastewater systems are handled at the Ringsend treatment works where measurements were taken. That adds up to around three-quarters of a tonne of the drug used in the Dublin area each year, notes Paull.
However while the study has yielded interesting statistics on the prevalence of the drug in society, the scientists stress that there are limitations to the approach they used. For example, it assumes that all cocaine detected came from human use, rather than being put directly into the water system, explains Paull.
"But I think if you measure the cocaine and assume that it all comes from human usage, then you have a reasonable answer that represents 10 per cent of what is actually being taken," he says.
The researchers have found "comparable levels" of cocaine residues in wastewater samples from Oslo, where they have been collaborating with Dr Kevin Thomas at the Norwegian Institute of Water Research. "Then there's the question of whether we want to do a longer-term study here, where we take samples and look at patterns over a year," says Paull.