A discovery as exciting as it is disturbing. Scientists have succeeded in capturing human DNA from the environment. This discovery could lead to applications for medicine, the environment or forensics. But it poses an ethical problem, given the ease with which these traces of human life have been collected, warn the authors of the study published Monday in Nature Ecology and Evolution. Surprised by the results of their work, they call for "safeguards" against privacy violations.

Recently developed, the environmental DNA technique is used to track wildlife and better understand biodiversity. It consists of taking samples from the animals' natural environments, which leave genetic traces in their wake via the cells (skin, hair, scales, etc.) that they lose permanently.

An unintentional discovery

The human being is no exception to the rule, spreading his DNA - the carrier of genetic information specific to each individual - wherever he goes: by treading the beach, swimming, coughing and postilloning in the air or flushing the toilet ... Usually stealthy footprints, which scientists did not expect to capture on such a large scale, according to the study.

This "unintentional taking of the human genome" began in the Whitney Marine Biodiversity Laboratory at the University of Florida, with sand samples to study the environmental DNA of sea turtles. The researchers expected to find some human DNA in the samples, which are often contaminated by the people handling them. But not in such large quantities, and of a quality "almost equivalent to that of a sample taken from a person," said David Duffy, a specialist in genetic diseases of wildlife at the University of Florida, who led the work.

Towards the identification of individuals

In the field, he and his team found human DNA fingerprints almost everywhere: in the ocean and rivers around the lab, near urban centers and in less populated places, on the sand of isolated beaches...

At a veterinary hospital, the collection of ambient air samples revealed the presence of DNA matching staff and animal viruses, the University of Florida said in a statement. The DNA sequences collected were long enough to be "readable" to identify mutations associated with diseases, such as diabetes, and determine genetic ancestry, said Mark McCauley, one of the lead authors. They were even able to sequence parts of the genome of volunteer participants who agreed to have their DNA taken from their sand fingerprints.

"For ethical reasons, we didn't look at our sequences so that we could identify specific individuals. But it is certain that this step will be taken one day. The only question is when," McCauley told a news conference.

Between hopes and worries

In the future, the collection of human environmental DNA could "benefit society", for example by helping to detect cancer mutations in wastewater, or to identify the suspect of a crime that has not left a more tangible trace, according to the Whitney laboratory researcher. But this raises as much hope as "serious concerns about genetic privacy and the limits of policing," said Natalie Ram, a law professor at the University of Maryland. In a commentary attached to the study, she points to a risk of "perpetual genetic surveillance."

These concerns are shared by the authors, who fear the technique could be misused to "track individuals or target certain ethnic minorities." There is also the question of consent to collect data that "floats freely in the air," says Mark McCauley. "This is why we are now alerting scientists and society to consider our results and develop the necessary regulation to frame research on human DNA," insists Professor Duffy.

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