Testing times: student rises to wastewater task

The importance of wastewater testing has come into its own with Covid-19.

At first, it was an early warning system to show where cases were located. These days, it’s proving there’s under-reporting of Covid cases.

Scientists at Waipapa Taumata Rau, University of Auckland, are involved in the powerful science of wastewater surveillance. The monitoring is best known for revealing the prevalence of the Covid-19 (SARS CoV-2) virus, but can also detect norovirus and even Ebola.

Doctoral candidate Mackay Price, supervised by Dr Sam Trowsdale, an urban hydrologist and senior lecturer in the School of Environment, is working on an aspect of this wastewater analysis.

“Luckily none of my work is particularly smelly,” says Mackay, promptly putting to bed the question of what it’s like to trawl through sewage.

“I’m helping to better understand the wastewater treatment plant catchments. So if we have detection in the wastewater, what that means in terms of the exact area it covers.”

Mackay says ethical questions sometimes arose about announcing where Covid-19 had been found in wastewater.

“The challenge faced by hydrologists and environmental scientists is how to communicate the information to the public and to decision makers to avoid issues of stigma.”

As far as Covid-19 measurements go, stigma is not such a concern these days, when the virus is being expelled into waste catchments all over the country. No one’s poo is sacred.

However, wastewater monitoring is used to assess other substances. Mackay’s masters research involved identifying drugs in wastewater.

“There’s perhaps more stigma attached to drugs, especially meth. If we detect meth in a certain community, how do we report this data so it doesn’t end up that a whole town becomes known as ‘the meth capital’ of New Zealand?”

Mackay and Sam have published a series of papers on wastewater-based epidemiology, including one looking at the ethics of wastewater surveillance for public health. It discusses the implementation of national-scale wastewater surveillance and the data being used for decision making by government departments.

It says: “Consent is not typically required for wastewater surveillance, which can exacerbate perceptions of risk and undermine public trust. Seemingly innocuous communication of surveillance data can stigmatise communities and perpetuate inequities.”

“Traditional media outlets love a catchy headline,” says Mackay. “The nuances and uncertainties of wastewater surveillance, a relatively new science, can be lost. If meth or Covid is found, what does that actually mean? And what are the appropriate actions?”

Mackay says while wastewater scientists will understand the finer details around results, people in public office may not, which means a lot of work needs to be done to communicate the information effectively. He observed this first-hand when he published a paper on drug use that was based on wastewater surveillance.

“On social media this got picked up in ways that aren’t possible to control, and twisted into a narrative such as ‘poor communities are like this, rich communities are like that’.”

He says while scientists generally have a social licence to do the testing, the absence of consultation may mean some people feel their rights are being infringed. In the US, some local governments have barred wastewater surveillance over fears of communities being labelled ‘drug towns’.

Mackay’s research involves analysing maps of all the wastewater treatment plants across New Zealand and ascertaining which suburbs are in each catchment.

“There are about 330 wastewater treatment plants and ESR monitors more than 100. So they cover a lot of the population, at least 85 percent, I would estimate. I’m helping refine some of the catchment maps, which involves going through the country’s treatment plants and checking ‘is this suburb in the catchment or not?’”

Mackay’s research also looks at the methods used in wastewater surveillance. “I’m looking at methodological improvements that apply to drugs or Covid-19, or whatever you’re testing for.”

Mackay’s undergraduate degree was in environmental science and geography but he is enjoying the transdisciplinary nature of his PhD – epidemiology, science, geography and health.

Covid-19 has supercharged interest and skills in wastewater-based epidemiology and surveillance – largely due to the pandemic.

“Wastewater surveillance has almost become a bit of a household name. Before, if I mentioned what we’re doing to my parents and my grandparents they’d say, ‘that sounds a bit weird and a bit smelly’. But later it was, ‘oh yes, I heard Ashley Bloomfield talking about that’.”

Mackay still has a few more years to go on the PhD but is looking to expand on his research in collaboration with ESR and New Zealand Police by combining data. “That’s when we’ll get meaningful insights about long-term trends, accounting for population size, which could lead to improved resources and decision making.”

Story by Denise Montgomery