Human DNA can be sequenced from small amounts of water, sand and air in the environment to extract potentially identifiable information such as genetic lineage, gender and health risks, according to our new research.

Every cell in the body contains DNA. Because each person has a unique genetic code, DNA can be used to identify individuals. Typically, doctors and researchers obtain human DNA through direct sampling, such as blood tests, swabs, or biopsies. However, all living things, including animals, plants, and microbes, are constantly shedding DNA. Water, soil and even the air contain microscopic particles of biological material from living organisms.

The DNA that an organism has shed into the environment is known as environmental DNA or eDNA. Over the past two decades, scientists have been able to collect and sequence eDNA from soil or water samples to monitor biodiversity, wildlife populations, and disease-causing pathogens. Tracking rare or elusive endangered species via their eDNA has been a boon to researchers, as traditional tracking methods such as observation or trapping can be difficult, often unsuccessful, and intrusive to the species of interest. https://www.youtube.com/embed/q7mp1wxLoyA?wmode=transparent&start=0 The authors and their colleagues use environmental DNA to study sea turtles.

Researchers using eDNA tools usually focus only on the species they are studying and ignore the DNA of other species. However, humans also shed, cough and dump DNA into their surroundings. And as our team of geneticists, ecologists and marine biologists at the University of Florida’s Duffy Lab discovered, signs of human life can be found in all but the most isolated places.

Animals, humans and viruses in eDNA

Our team uses environmental DNA to study endangered sea turtles and the viral cancers they are susceptible to. Baby hatching sea turtles lose their DNA as they crawl along the beach to the ocean shortly after birth. The sand collected from their tracks contains enough DNA to provide valuable information about turtles and the chelonid herpesviruses and the fibropapillomatous tumors that afflict them. Collecting a quart of water from the tank of a recovering sea turtle under veterinary care equally provides a wealth of genetic information for research. Unlike blood or skin sampling, eDNA collection does not cause stress to the animal.

The genetic sequencing technology used to decode DNA has improved rapidly in recent years and it is now possible to easily sequence the DNA of any organism in a sample from the environment. Our team suspected that the sand and water samples we were using to study sea turtles also contained DNA from a number of other species, including, of course, humans. What we didn’t know was how informative the human DNA we could extract would be.

To figure this out, we took samples from a variety of locations in Florida, including the ocean and rivers in urban and rural areas, the sand of isolated beaches, and a remote island people never usually visit. We found human DNA in all those places except the remote island, and these samples were of sufficient quality for analysis and sequencing.

We also tested the technique in Ireland, tracing along a river that winds its way from a remote mountaintop, through small rural villages, and into the sea in a larger city of 13,000. We found human DNA everywhere except in the remote mountain tributary where the river originates, away from human settlement.

We also collected air samples from a room at our Wildlife Veterinary Hospital in Florida. The people in the room gave us permission to take samples from the air. We recovered DNA matching people, the animal patient, and common animal viruses present at the time of collection.

Surprisingly, the human eDNA found in the local environment was intact enough for us to identify mutations associated with the disease and determine the genetic ancestry of people living in the area. DNA sequencing that the volunteers left in their footprints in the sand even yielded parts of their sex chromosomes.

Diagram illustrating eDNA collection sources and analysis workflow
Human eDNA can be collected and analyzed from a variety of sources. Liam Whitmore/Created with BioRender.com, CC BY-NC-ND

Ethical implications of human eDNA collection

Our team believes that the unintentional recovery of human DNA from environmental samples is human genetic bycatch. We call for a more in-depth discussion of how to handle human environmental DNA ethically.

Human eDNA could present significant advances to research in fields as diverse as conservation, epidemiology, forensic science and agriculture. When handled properly, human eDNA could help archaeologists trace unknown ancient human settlements, allow biologists to track cancer mutations in a given population, or provide law enforcement agencies with useful forensic information.

However, there are also a myriad of ethical implications related to the unintentional or deliberate collection and analysis of human genetic bycatch. Identifiable information can be extracted from eDNA, and accessing this level of detail about individuals or populations comes with responsibilities for consent and confidentiality.

While we conducted our study with the approval of our institutional review board, which ensures that studies in people adhere to ethical research guidelines, there is no guarantee that everyone will treat this type of information ethically.

Many questions arise regarding human environmental DNA. For example, who should have access to human eDNA sequences? Should this information be made public? Should consent be sought before taking human eDNA samples and from whom? Should researchers remove human genetic information from samples originally collected to identify other species?

We believe it is essential to implement regulations that ensure that the collection, analysis and storage of data are carried out ethically and appropriately. Policymakers, scientific communities, and other stakeholders need to take human eDNA collection seriously and balance consent and privacy with the possible benefits of studying eDNA. Raising these questions now can help ensure that everyone is aware of eDNA’s capabilities and provide more time to develop protocols and regulations to ensure appropriate use of eDNA techniques and ethical handling of human genetic captures.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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