Your e-DNA is in some seriously weird places – here’s why that’s a big privacy concern

We leave traces of ourselves everywhere we go. Like snakes (but without the drama) we shed our dead skin and hair. We cough and spit, or flush the DNA in our body’s waste into the environment, and – on a bad day – we bleed into our surroundings too.

Now, scientists have discovered that this human DNA can be pulled out of water, earth, and literally ‘thin air’ – and is strong enough to be matched to individuals. The University of Florida researchers found human DNA almost everywhere – swirling through oceans and rivers or buried in the sand of beaches. They are calling this ‘human genetic bycatch’.

“We were absolutely shocked to find more DNA from the general public in the river systems around the institute than we were from our own facility,” Dr David Duffy, an assistant professor of wildlife disease genomics at the University of Florida and one of the authors of the paper, toldBBC Science Focusand other publications.

Environmental DNA, or e-DNA, is free-floating fragments of tissues or other biological material that circulates through terrestrial and aquatic ecosystems. It’s often used in scientific investigations to monitor biodiversity, trace diseases or track invasive species.

But the study published inNature Ecology & Evolution reveals that human DNA can be collected and identified just as easily as these target species.

The researchers discovered this almost by accident. When tracing the viral cancers causing a sea turtle pandemic, they expected to find some human e-DNA – particularly in their own labs – but not to find it almost everywhere they looked. The only places human e-DNA was not found was remote islands and mountaintops.

Read more:

• How we unravelled the structure of DNA
• Environmental DNA and the hunt for marine species

These aren’t just traces: according to Duffy, the DNA samples they found allow the same level of advanced study as DNA taken directly from individuals themselves. “What was really surprising was the quantity and quality,” he said. “There are some other studies where trace amounts of human DNA have been picked up, but never really to this level.”

We’re talking such high-quality DNA that the researchers would have been able to sequence it to identify the owner’s genetic ancestry, or detect mutations linked to genetic diseases like autism and diabetes.

Except that they didn’t sequence all of the DNA they found – only that of volunteers who had consented for this to happen. To do so would have embroiled the researchers in an ethical dilemma: while scientific investigations of this kind will often share the study’s findings publicly, in this case that would mean sharing incredibly sensitive information about specific individuals.

Anyone would be to access and harvest this information – not just about where an individual had been, but also the specifics of their health and ancestry. In the future, the researchers warn that this could even enable the tracking of individuals or specific ethnic groups through the environment.

The findings do also present beneficial opportunities, including forensic use in criminal investigations – like identifying suspects from the DNA in the air of a crime scene. It could also advance study in the research fields of medicine, environmental science, and archaeology. Archaeologists, for example, could uncover archaeological sites by searching for hidden human DNA.

Either way, the study highlights an urgent need for policymakers to tackle issues of consent and privacy when it comes to e-DNA.

“This collection of human e-DNA is an issue that's going to grow over time,” according to Duffy.

“We can't just ignore that there's all of this human data potentially being accumulated,” he added.

“That’s the case for policymakers and scientists to sit down and decide how we should take this technology forward, what sorts of checks and balances that may need to be put in place before it's more widely used.”