David Duffy, a wildlife geneticist at the University of
Florida, just wanted a better way to track disease in sea turtles. Then he
started finding human DNA everywhere he looked.
اضافة اعلان
Over the past decade, wildlife researchers have refined
techniques for recovering environmental DNA, or eDNA — trace amounts of genetic
material that all living things leave behind. A powerful and inexpensive tool
for ecologists, eDNA is all over — 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
wildlife populations, and even to rediscover species thought to be extinct. The
eDNA technology is also used in wastewater surveillance systems to monitor
COVID and other viruses.
But all along, scientists using eDNA were quietly recovering
gobs and gobs of human DNA. To them, it’s pollution, a sort of human genomic
bycatch muddying their data. But what if someone set out to collect human eDNA
on purpose?
New DNA collecting techniques are “like catnip” for law
enforcement officials, says Erin Murphy, a law professor at the New York
University School of Law who specializes in the use of new technologies in the
criminal legal system. Police have been quick to embrace unproven tools,
including using DNA to create probability-based sketches of a suspect.
That could pose dilemmas for the preservation of privacy and
civil liberties, especially as technological advancement allows more
information to be gathered from ever smaller eDNA samples. Duffy and his
colleagues used a readily available and affordable technology to see how much
information they could glean from human DNA gathered from the environment in a
variety of circumstances, such as from outdoor waterways and the air inside a
building.
The results of their research, published Monday in the
journal Nature Ecology & Evolution, demonstrate that scientists can recover
medical and ancestry information from minute fragments of human DNA lingering
in the environment.
Forensic ethicists and legal scholars say the Florida team’s
findings increase the urgency for comprehensive genetic privacy regulations.
For researchers, it also highlights an imbalance in rules around such
techniques in the US — that it is easier for law enforcement officials to
deploy a half-baked new technology than it is for scientific researchers to get
approval for studies to confirm that the system even works.
Genetic trash to genetic treasure
It has been clear for decades that fragments of our DNA
cover the planet like litter. It just did not seem to matter. Scientists
believed DNA in the environment was too small and too degraded to be
meaningfully recovered, much less used to identify an individual human being,
unless it came from distinct samples such as a bloodstain or an object someone
had touched.
Wildlife researchers embraced environmental DNA anyway
because they are only looking for very small segments of DNA — scanning for
what they call bar codes that will identify the creatures in a sample to a
species level. But after finding “surprising” levels of human eDNA in their
samples while monitoring disease in Florida sea turtles, Duffy and his team set
out to get a more accurate picture of the condition of human DNA in the
environment, and to see how much information it could reveal about people in an
area.
As a proof of concept in one of their experiments, the
researchers scooped up a soda-can-size sample of water from a creek in St.
Augustine, Florida. They then fed the genetic material from the sample through
a nanopore sequencer, which allows researchers to read longer stretches of DNA.
The one they used cost about $1,000, is the size of a cigarette lighter, and
plugs into a laptop like a flash drive.
From the samples, the team recovered much more legible human
DNA than they had anticipated. And as knowledge expands about human genetics,
analysis of even limited samples can reveal a wealth of information.
The researchers recovered enough mitochondrial DNA — passed
directly from mother to child for thousands of generations — to generate a
snapshot of the genetic ancestry of the population around the creek, which
roughly aligns with the racial makeup reported in the latest census data for
the area (although the researchers note that racial identity is a poor proxy
for genetic ancestry). One mitochondrial sample was even complete enough to
meet the requirements for the federal missing persons database.
Surveillance and forensics
Anna Lewis, a Harvard researcher who studies the ethical,
legal, and social implications of genetics research, said that environmental
DNA hadn’t been widely discussed by experts in bioethics. But after the
findings from Duffy and his colleagues, it will be.
Technology focused on eDNA, she said, could be used for
surveillance of certain kinds of people — for example, people with a specific ancestral
background or with particular medical conditions or disabilities.
The implications of such uses, researchers agree, depend on
who is using the technology and why. Although pooled eDNA samples could help
public health researchers determine the incidence of a mutation that causes a
disease in a community, that same eDNA sample could equally be used to find and
persecute ethnic minorities.
“This gives a powerful new tool to authorities,” Lewis said.
“There’s internationally plenty of reason, I think, to be concerned.” Countries
such as China already conduct extensive and explicit genetic tracking of
minority populations, including Tibetans and Uyghurs. Tools such as eDNA
analysis could make it that much easier, she said.
How much of an ethical minefield eDNA research will be also
depends on the extent to which it’s possible to identify an individual. In some
situations, it’s already achievable.
The kind of genetic data Duffy recovered from public places
wouldn’t work with the methods law enforcement personnel in the US currently
use to identify individuals, said Robert O’Brien, a forensic biologist at
Florida International University and a former crime laboratory DNA analyst.
When law enforcement DNA analysts compare a crime-scene
sample to a suspect, they’re looking at 20 markers spread across the human
genome that are tracked by the FBI’s Combined DNA Index System, or CODIS,
O’Brien said. Those markers are only useful if there’s certainty that several
of them come from the same person, and because the eDNA fragments Duffy studied
can’t capture more than one marker at a time, a public place such as the
Florida stream becomes a nightmarish jigsaw puzzle.
However, forensic researchers suggest that individual
identification from eDNA could already be possible in enclosed spaces where
fewer people have been. In October, a team from the Oslo University Hospital’s
forensic research center piloted a new technique to recover human DNA from air
samples and was able to construct full CODIS profiles from airborne DNA inside
an office.
Who gets access when DNA is free for the taking?
In the US, rules vary widely for who is allowed to capture
and analyze DNA.
University scientists hoping to learn more about human eDNA
must justify the scope and privacy concerns of their studies in an imperfect
process involving ethics boards at their institutions that can limit or reject
experiments. But there are no such guardrails for law enforcement officials
trying out a new technology.
“There’s an imbalance in almost all systems of the world
between what law enforcement is allowed to do, versus publicly funded research,
versus private companies,” said Barbara Prainsack, a professor at the
University of Vienna who studies the regulation of DNA technology in medicine
and forensics.
Some countries, including Germany, have an approved green
list of technologies and forms of evidence that law enforcement agencies can
use, but it’s exactly the reverse in the United States.
“It’s a total Wild West, a free-for-all,” said Murphy. “The
understanding is police can sort of do whatever they want unless it’s
explicitly prohibited.”
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