Traces of Human DNA Are Everywhere in the Environment

May 15, 2023
Dennis Thompson HealthDay Reporter

Detailed remnants of human DNA can be found just about everywhere that people have been, a surprising finding that raises a host of ethical issues for researchers, a new study says.

Environmental samples of human DNA were found nearly everywhere, save for isolated islands and remote mountaintops where people have never visited, researchers said. While sequencing this DNA offers researchers consistent data, it also presents an ethical dilemma because it reveals so much personal genetic information.

"We've been consistently surprised throughout this project at how much human DNA we find and the quality of that DNA,"David Duffy, a professor of wildlife disease genomics at the University of Florida in Gainesville, said in a school news release. "In most cases the quality is almost equivalent to if you took a sample from a person."

The DNA samples were of such high quality that scientists could identify mutations associated with disease and determine the genetic ancestry of nearby populations, researchers reported.

In fact, environmental human DNA even could provide specific genetic information about individual volunteers, the investigators discovered.

The research started from an attempt to study endangered sea turtles and viruses that can cause cancer in them by gathering environmental turtle DNA from the tracks they leave in the sand.

Scientists found human DNA in their turtle samples, raising the question of where else people might have coughed, spit, shed and flushed genetic samples in the environment.

Modern genetic sequencing technology makes it relatively easy to sequence the DNA of every organism in an environmental sample, researchers noted. They wondered how much human DNA there would be in samples taken from various places, and whether it was intact enough to harbor useful information.

Duffy's team found quality human DNA in the ocean and rivers surrounding UF's Whitney Laboratory for Marine Bioscience and Sea Turtle Hospital in St. Augustine. The DNA was found close to town, far from human settlement, and even in the sand from isolated beaches.

The researchers also traveled to a remote island never visited by people, and found it free of human DNA -- at least until they showed up. They were able to retrieve DNA from the footprints that volunteers left in the sand, and these samples were good enough to allow some genetic sequencing.

Duffy also tested the technique during a trip to his native Ireland. He followed a river that winds through town on its way to the ocean and found human DNA everywhere but the remote mountain stream where the river starts, far from civilization.

Researchers also collected room air samples from a veterinary hospital and recovered DNA matching the staff, the animal patient and common animal viruses.

These sort of environmentally collected DNA samples could, if ethically handled, prove a boon to a number of research fields ranging from medicine to archaeology to criminal forensics.

For example, scientists could track cancer mutations from wastewater samples or locate undiscovered archaeological sites by checking for hidden human DNA. Detectives could identify suspects from the DNA floating in the air of a crime scene.

But because humans can't help but leave DNA samples in their wake, scientists and regulators will need to grapple with the ethical dilemmas inherent in the widespread availability of precious human genetic information.

Ethical standards and guardrails are needed to govern this kind of research, since it has the ability to potentially identify individuals down to a genetic level.

"It's standard in science to make these sequences publicly available. But that also means if you don't screen out human information, anyone can come along and harvest this information,"Duffy said. "That raises issues around consent. Do you need to get consent to take those samples? Or institute some controls to remove human information?"

Policymakers and scientific communities need to seriously weigh issues around consent and privacy, and balance them against the possible benefits of studying this errant DNA, Duffy said.

"Any time we make a technological advance, there are beneficial things that the technology can be used for and concerning things that the technology can be used for. It's no different here,"he said. "These are issues we are trying to raise early so policy makers and society have time to develop regulations."

The findings were published May 15 in the journal Nature Ecology and Evolution.

More information

The World Wildlife Fund has more on environmental DNA sampling.

SOURCE: University of Florida, news release, May 15, 2023

DNA Genetics