By: Jamie Morton
It’s a disgusting idea for most of us, but scientists say sampling our sewage on a mass scale – or “one large urine test”, as they’ve called it – has endless potential.
Already, tests at city wastewater treatment plants have revealed fascinating insights into our use of illicit drugs.
But Kiwi scientists say there are countless other discoveries waiting to be made in the burgeoning field of “wastewater-based epidemiology” – among them monitoring contaminants, disease, and even obesity.
Information about a whole population’s exposure to agents and disease can be revealed by picking up signature biomarkers among collective wastewater samples.
It’s currently being targeted at use of drugs methamphetamine, cocaine, heroin, alpha PVP, MDMA and creatinine in a project between police and ESR at Christchurch and Auckland treatment plants.
The latest figures suggest there are around 388,000 illegal drug users in New Zealand.
But such data – based off crime statistics, medical records, drug production and seizure rates – are considered notoriously inaccurate for assessing what’s a $1.8b problem.
Traditional analysis approaches were also time-consuming and limited in picking up changing patterns or differences between local communities.
When the joint-agency National Drug Intelligence Bureau commissioned ESR to build the country’s first state-funded wastewater drug testing programme two years ago, it was a first.
But the bureau’s boss, John O’Keeffe, said following Australia in turning to the method was well worth the investment, which itself was funded by seized proceeds of crime.
Customs NZ had also used the data to inform its work at the border.
“For us, up until now, reliable data about the volume of illegal drugs used by the population was difficult to obtain,” O’Keeffe said.
“Wastewater testing provides an accurate measure of illegal drug consumption that is cost effective, timely and non-intrusive.”
Flushing out our drug habits
ESR scientists spent a year sampling wastewater over seven consecutive days each month, meaning patterns could be pinpointed on week-to-week and annual scales.
It also gave agencies near real-time intelligence about what drugs – excepting cannabis – were flowing through cities.
They found meth was the main drug of choice in Auckland and Christchurch, with habitual use throughout the week, while cocaine and MDMA were more likely used recreationally as their traces spiked over weekends.
Auckland’s sampling turned up a higher proportion of cocaine consumption than Christchurch, which could be explained by community demographics and the drug’s high street price.
Traces of heroin and a-PVP were yet to be detected.
ESR chemist Andrew Chappell explained that whatever people consume was metabolised by the body into other compounds, before they were excreted and make their way into the wastewater system.
When drugs were consumed, a mixture of the parent compounds of the drug taken and associated metabolites were also excreted, and could be traced based on a method that was developed as recently as 2011.
“We don’t just look for the drugs themselves but for the biomarkers – that is the unique metabolites that humans excrete from their system after using drugs.”
Chappell and his colleagues were using what’s called a solid phase extraction machine, able to extract and concentrate drugs and other compounds from the wastewater.
“The metabolites that are indicators of the drugs present in the wastewater are extremely diluted,” he said.