Study shows we leave a trail of DNA behind us - even on the beach

Monitoring of endangered sea turtles inadvertently identifies human traces, raising surveillance concerns

Footprints are not the only trace that humans leave behind on a walk on the beach. Amy Leang / The National

People leave behind their DNA in the air that they breathe, in footprints in the sand and in the water close to where they live, a new study has discovered.

The findings come from a research project that analysed DNA “fingerprints” to study the health and locations of endangered sea turtles.

The scientists, most from the University of Florida, said that their detection of human DNA “raises ethical dilemmas” around consent, privacy, surveillance and data ownership.

'Substantial amounts of data'

Known as “human genetic bycatch”, the environmental DNA or eDNA has been detected at a time when reduced sequencing costs make its analysis much easier and cheaper.

With the eDNA data they collected in their new study, the researchers could identify the genetic heritage of the people living locally.

They also identified genetic mutations linked to conditions including autism, diabetes, eye diseases and heart diseases, the scientists wrote in Nature Ecology & Evolution.

The researchers said that even in areas with relatively low human population density, they “nevertheless inadvertently captured a substantial amount of human genomic data”.

Genomic refers to all of an organism's genetic material.

When it came to the act of collecting this data, researchers said that taking eDNA samples from some locations, such as popular tourist beaches, is likely to be “less ethically concerning” than monitoring samples of wastewater from “small, defined, stable populations”.

Blurring boundaries

However numerous “problematic implications” from the capture of human eDNA are highlighted in the study, some of which may be inadvertent, such as being able to track people.

A string of malicious applications also potentially open up, including the ability to harvest genetic data about particular ethnic groups.

Civil liberties organisations are becoming increasingly concerned about the way that DNA shed from people's skin, blood, saliva, sweat, nasal mucus and hair may be used.

“As long as we live in the world and leave our homes each day, we can’t avoid leaving a trail of our DNA in our wake,” the American Civil Liberties Union said.

“Every strand of DNA holds a treasure trove of deeply personal information, from our propensity for medical conditions to our ancestry to our biological family relationships.”

The ACLU has raised concerns about, for example, what it describes as the authorities in the US “surreptitiously collecting and testing people’s DNA without the protections and constraints of a warrant”, such as from discarded napkins or disposable cutlery.

No immediate danger

Prof Yves Moreau, from Leuven University in Belgium, who analyses genetic data, said he did not think that the new study, which he was not involved with, raised any “immediate concerns” in terms of authorities being able to track people.

However, he said that the research was “really quite important by highlighting how pervasive” the spread of our DNA was.

It was already known, Prof Moreau said, that people leave DNA in many locations, even on door handles, but the analysis of such “touch DNA” or “trace DNA” faces serious technical challenges, although they may be overcome by technology.

“Currently the landscape around DNA collection is very unclear,” he said. “The American Civil Liberties Union has argued because we cannot control where our DNA goes. We need to have that privacy respected as if it’s on your person.

“We need to have … a really good framework everywhere in the world that limits where and how our DNA is collected.”