During the announcement of the 2017 budget, Treasurer Scott Morrison signalled the Coalition plans to use wastewater monitoring to help the government profile, identify and target welfare recipients with potential drug dependencies.

It appears the government’s plans to profile individuals with drug dependencies using sewage samples hinges upon the Australian Criminal Intelligence Commission’s (ACIC) National Wastewater Drug Monitoring Program. 

This is odd, because as far as I can tell, the scientists from the University of Queensland and the University of South Australia who were commissioned to deliver and prepare the first National Wastewater Drug Monitoring Program Report — the capability the government are relying on to profile Centrelink recipients with drug dependencies — have been incredibly quiet about the government’s decision to use their work to persecute welfare users. 

One begins to wonder if the scientists involved in preparing the ACIC report even knew their work would eventually be used to try to track individual drug users? 

So can the type of water quality analysis as used by the ACIC pinpoint individual drug users? 

Meet Stuart Khan. He’s a scientist and a water quality specialist who wants to tell you why the government’s wastewater testing plans to profile these individuals simply won’t work. 

“I’ve been measuring pharmaceuticals, drugs and other trace chemicals in sewage for over 20 years. I did my PhD on this topic and have published over 100 research papers on it. So I have a reasonable understanding of what can and can’t be achieved by it,” Khan said.

“It is possible to measure very low concentrations of some of these chemicals in raw sewage and, in some cases, that can provide useful information about patterns of drug use in the community. It’s an interesting idea and many research groups around the world have now had a go at it.

Khan says measuring traces of drugs in sewage won’t give the government a reliable sense of which suburbs to target when drug-testing Centrelink recipients.

“But people who have paid close attention to the science realise that the level accuracy in translating raw sewage concentration data to community drug use is very low. This is especially true when you try to break it down to a suburb-by-suburb level.”

“One reason is that the measured concentrations in raw sewage fluctuate wildly. The sample sizes are necessarily very small (usually 1L) and not representative of the huge variation in concentrations of these chemical in raw sewage. This is mainly a problem in small sewage catchments, as you would have if you try to look at the problem on a suburb-by-suburb level. In such cases, you could take three samples a minute apart and get as much variability among them as you get by monitoring different locations.”

Khan says the composition of trace chemicals in small sewage catchments, such as drugs and pharmaceuticals, varies due to the randomness of when people use and flush a toilet, compared to generating other sources of sewage such as using showers, baths, dishwashers, and so on.

“In order to calculate the ‘load’ of the chemical being transported down a sewer, you need to understand both the concentration variability and the flow rate variability in fairly precise way. Neither of these sources of variability are easy to determine in a small sewage catchment, hence they are generally very poorly understood. 

“In a very large sewage catchment (such as most of Sydney mixed together), the variability is less since you get an ‘averaging’ effect from mixing many sources.” 

Khan also says there are other reasons — unrelated to drug use patterns or household activity — why sewage concentrations fluctuate.

“These include the level of groundwater or storm water intrusion into sewers, as well as other factors that affect the concentration of sewage. These can be highly variable from one suburb to another.”

“My concern is that, due to the high-tech nature of the water quality analysis, law enforcement officials and others may make the mistake of assuming the measured concentrations are accurate reflections of patterns of drug use in the community. The truth is, they are far from accurate.”

“It is because of this lack of accuracy — and lack of understanding of accuracy — that I could not support the use of these data in any way that affected individuals on a personal level. It’s far too random as a measurement to be used as evidence against a community.”

You heard it from the expert: the government’s proposed wastewater testing measures are “far from accurate” and “too random to be used as evidence against a community” — let alone individual welfare recipients.