Wastewater surveillance provides crucial COVID data, but also carries privacy concerns: scientists
Researchers say data from your poop is anonymous. Steve Hrudey says we need more assurances
Throughout the COVID-19 pandemic, wastewater surveillance and analysis became a key tool in monitoring and measuring the amount of virus in communities.
But some experts caution that the data collected from these studies could also lead to privacy concerns, especially because samples are often gathered from public sources without individual consent.
"Bioethics, which sort of underlies what health-care providers do, has historically been based upon 'do no harm' — and the idea of informed consent," said Steve Hrudey, a professor emeritus from the University of Alberta's department of laboratory medicine and pathology. "Well, informed consent is really not possible for this kind of technique."
Hrudey is chair of the national research advisory group for the COVID-19 Wastewater Coalition, a non-profit group founded in the spring of 2020 that helps co-ordinate and share information about wastewater surveillance efforts across the country.
A 2021 paper co-authored by Hrudey and six other researchers recommended that wastewater surveillance programs for COVID-19 follow a list of 17 guidelines presented by the World Health Organization for ethical public health surveillance.
Those guidelines suggest that surveillance programs should follow four main goals: working toward the common good, equity, respect for persons and good governance.
"The case for maximizing the potential of this approach is compelling, but the benefits of wastewater surveillance must clearly outweigh the ethical risks for the community," the paper reads.
The poop doesn't lie
Humans can shed genetic material of the SARS-CoV-2 virus in the form of RNA. Sometimes the virus can be detected in human wastewater samples before someone displays symptoms of the disease.
"If you're shedding it right away, within days of being infected, that information is already being flushed down the toilet [and] travelling to your wastewater treatment plant where it's being collected and analyzed by, you know, us or someone like us," said Newsha Ghaeli, co-founder of wastewater epidemiology company Biobot Analytics.
Ghaeli, who studied in Waterloo, Ont., and Montreal before co-founding Biobot in the U.S., said the technology used by her company can currently detect a positive case in a sample from a population of 6,500 people.
That data has become increasingly important as provinces and territories scaled back access to PCR tests in the latter half of 2021, particularly as the Delta and later Omicron waves saw significant spikes in reported and suspected positive cases.
Experts like Ghaeli say that while the data can be very precise, there's no way to identify an individual even if they detect a single positive case.
Your poop doesn't have identifying information like a fingerprint, as it were.
"When we get a positive test, there's no way we know who it came from. You know, it's like saying, 'Oh, we have so many cars on the 401 today.' You have no idea who's driving those cars," said Kim Gilbride, a professor and molecular microbiologist at Toronto Metropolitan University's Gilbride Lab for wastewater surveillance.
Sludge life, poop pellets
Gilbride's lab analyzes sewage samples that are delivered from across the Greater Toronto Area: some from hospitals, long-term care homes, while others come from the Humber Wastewater Treatment Plant.
Those bottles are mostly filled with cloudy water, but some of them are more opaque and labelled "sludge."
"When you open one of those — yeah, you got to duck for cover," said Babneet Channa, a research assistant who helps process the samples.
Channa and another assistant Matthew Santilli mostly work with equipment that's fitted with a fume hood to vent those odours. They put the samples into test tubes that spin inside a centrifuge — rendering the sludge into a relatively inert, pea-sized pellet for analysis.
"It's anonymous. We don't really, like, go after people and say, 'It's you,' you know, or 'It's your house,'" said Nora Dannah, a post-doctoral researcher who also works at the lab.
Data could help or hurt people in neighbourhoods: Hrudey
That's not enough to assuage Hrudey's concerns, who says that "you can zero in on very small areas" if samples are identified and gathered from specific sewer networks in a city.
With narrow enough data, public health officials could deploy to a neighbourhood to prevent outbreaks from spreading further. But it could also be misused to stigmatize the people living there — or worse, Hrudey warned.
It isn't purely theoretical either, he said.
There have been cases in Hong Kong and Singapore where wastewater surveillance has been used in apartment buildings and then authorities have tracked down positive samples from individual apartments, Hrudey said.
"The authorities have shown up and said, 'Well, you know, you've got a case here and you need to be tested,'" he said.
"Now, you can argue that there's a public health rationale for that. But you can see there's a slippery slope possible."
Hrudey also said he'd seen a draft research proposal that suggested it might be possible to chart a neighbourhood's infection rates of COVID or other traceable diseases down to the block.
"It was in enough detail that you could almost identify the street addresses," he said.
He stressed, however, that the proposal was theoretical — only presenting what might be possible — and is not aware that anyone in Canada has attempted this or has been granted access to private citizens' data to use it.
"Health authorities are bound, at least in Alberta and I suspect in most provinces, by very strict privacy legislation concerning individually identifiable health records," he wrote to The Sunday Magazine in a follow-up email.
He isn't the only one to raise these concerns.
A 2021 article in the European Journal of Law and Technology, by Dutch scientist Bart van der Sloot, posits potential future uses that almost read like science fiction: wastewater surveillance robots that could crawl through residential pipes, taking samples from a single street or even a single home.
Ghaeli agrees that a more definitive ethical groundwork needs to be laid out for how wastewater surveillance is used — and sooner rather than later. But we're not there yet, she said.
"I think that within a year or so we'll be in a different place, because it's absolutely necessary for us to, I think, talk through and hammer out these tough questions," she said.
With files from Peter Mitton. Radio segment produced by Peter Mitton.
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