Chance of DNA being extracted from the air worries experts – 05/17/2023 – Science

David Duffy, a wildlife geneticist at the University of Florida, just wanted a better way to identify disease in sea turtles. Then he started finding human DNA everywhere he looked.

Over the past decade, wildlife researchers have refined techniques for recovering environmental DNA, or eDNA—the vestiges of genetic material that all living things leave behind. A powerful yet inexpensive tool for ecologists, eDNA is everywhere — floating in the air or lingering in water, snow, honey and even your cup of tea.

Researchers have used the method to detect invasive species before they take over, to track vulnerable or secretive wild populations, and even to rediscover species thought to be extinct. eDNA technology is also used in wastewater surveillance systems to monitor the Covid and other viruses.

But all the time scientists using eDNA were silently recovering mounds of human DNA. For them it’s pollution, a kind of bycatch of the human genome that confuses their data. But what if someone decides to collect human eDNA on purpose?

New DNA collection techniques are “a big draw” for law enforcement, says Erin Murphy, a law professor at New York University School of Law who specializes in the use of new technologies in the criminal justice system. Police quickly adopted unproven tools, including using DNA to create probability-based sketches of a suspect.

This can pose dilemmas for the preservation of privacy and civil liberties, especially as technological advances allow more information to be gleaned from ever smaller samples of eDNA. Duffy and his colleagues used readily available technology to see how much information they could extract from human DNA collected from the environment in a variety of circumstances, such as outdoor waterways and the air inside a building.

The results of their research, published on Monday (15) in the journal Nature Ecology & Evolution, demonstrate that scientists can recover medical and ancestral information from tiny fragments of human DNA remaining in the environment.

Forensic ethicists and legal experts say the Florida team’s findings add to the urgency of comprehensive genetic privacy regulations. For the researchers, it also highlights an imbalance in the rules surrounding these techniques in the United States — it’s easier for law enforcement officials to use a new semi-ready technology than it is for scientific researchers to get approval for studies to confirm that the system works.

From genetic junk to genetic treasure

It’s been clear for decades that fragments of our DNA litter the planet like garbage. It just didn’t seem to matter. Scientists believed that DNA in the environment was too small and too degraded to be recovered in any meaningful way, let alone be used to identify a human individual, unless it came from distinct samples, such as a bloodstain or an object someone had touched. .

Wildlife researchers approved of environmental DNA anyway because they’re only looking for very small segments of DNA — scanning what they call barcodes that will identify creatures in a species-level sample. But after finding “surprising” levels of human eDNA in their samples while monitoring diseases in Florida sea turtles, Duffy and his team decided to get a more accurate picture of the condition of human DNA in the environment and see how much information it could reveal about the conditions. people in an area.

As a proof of concept in one of their experiments, the researchers took a water sample from a stream in St. Augustine, Florida. They then fed the sample’s genetic material through a nanopore sequencer, which allows researchers to read longer stretches of DNA. The one they used costs around $1,000, is about the size of a cigarette lighter, and plugs into a laptop like a thumb drive.

From the samples, the team recovered much more readable human DNA than anticipated. And as knowledge of human genetics expands, analysis of even limited samples can reveal a wealth of information.

The researchers recovered enough mitochondrial DNA—passed directly from mother to child over thousands of generations—to generate a snapshot of the genetic ancestry of the population around the creek, which roughly matches the racial makeup reported in the latest census data for the area (although researchers note that racial identity is a poor proxy for genetic ancestry). A mitochondrial sample was sufficiently complete to meet federal missing persons database requirements.

Surveillance and expertise

Anna Lewis, a Harvard researcher who studies the ethical, legal and social implications of genetic research, said that environmental DNA has not been widely discussed by experts in bioethics. But it will be, after the findings of Duffy and his colleagues.

Technology focused on eDNA, she said, could be used for surveillance of certain types of people — for example, people with a specific ancestral background or with specific medical conditions or disabilities.

The implications of such uses, researchers agree, depend on who is using the technology and why. While pooled eDNA samples can help public health researchers determine the incidence of a disease-causing mutation in a community, that same eDNA sample can be used to find and pursue ethnic minorities.

“It provides a powerful new tool for law enforcement,” said Lewis. “I think internationally there’s a lot to be concerned about.” Countries like China already carry out extensive and explicit genetic screening of minority populations, including Tibetans and Uyghurs. Tools like eDNA analysis can make this much easier, she said.

How much of an ethical minefield will also be eDNA research will depend on the extent to which an individual can be identified. In some situations, this is already achievable.

The kind of genetic data Duffy retrieved from public places wouldn’t work with the methods US law enforcement currently uses to identify individuals, said Robert O’Brien, a forensic biologist at Florida International University and a former crime lab DNA analyst. .

When police DNA analysts compare a crime scene sample to a suspect, they look at 20 markers scattered across the human genome that are tracked by the FBI’s Combined DNA Index System, or Codis, O’Brien said. These markers are only useful if you are certain that several of them come from the same person, and since the eDNA fragments studied by Duffy cannot capture more than one marker at a time, a public place like the Florida creek becomes a terrible nightmare.

However, forensic researchers suggest that individual identification of eDNA may already be possible in closed spaces where fewer people have been. In October, a team from the forensic research center at the University Hospital in Oslo (Norway) tested a new technique for recovering human DNA from air samples and managed to build complete Codis profiles of airborne DNA inside an office.

Who has access when DNA is available?

In the United States, rules vary widely about who is allowed to collect and analyze DNA. University scientists who wish to learn more about human eDNA must justify the scope and privacy concerns of their studies in an imperfect process involving ethics boards from their institutions, which can limit or reject experiments.

But there are no protective barriers for law enforcement trying out a new technology.

“There is an imbalance in almost every system in the world between what law enforcement can do, versus publicly funded research, versus private companies,” said Barbara Prainsack, a professor at the University of Vienna (Austria) who studies the regulation of DNA in medicine and forensic medicine.

Some countries, including Germany, have an approved green list of technologies and forms of evidence that law enforcement bodies can use, but the exact opposite is true in the United States.

“It’s a total western, a free-for-all,” Murphy said. “The understanding is that the police can do whatever they want unless it is explicitly prohibited.”

^{Translated by Luiz Roberto M. Gonçalves}