Everywhere they go, humans leave stray DNA. Police have used genetic sequences retrieved from cigarette butts and coffee cups to identify suspects; archaeologists have sifted DNA from cave dirt to identify ancient humans. But for scientists aiming to capture genetic information not about people, but about animals, plants, and microbes, the ubiquity of human DNA and the ability of even partial sequences to reveal information most people would want to keep private is a growing problem, researchers from two disparate fields warn this week. Both groups are calling for safeguards to prevent misuse of such human genomic “bycatch.”

Genetic sequences recovered from water, soil, and even air can reveal plant and animal diversity, identify pathogens, and trace past environments, sparking a boom in studies of this environmental DNA (eDNA). But the samples can also contain significant amounts of human genes, researchers report today in Nature Ecology & Evolution. In some cases, the DNA traces were enough to determine the sex and likely ancestry of the people who shed them, raising ethical alarms…Similarly, scientists have for decades analyzed the genetic information in fecal matter to reveal the microbes in people’s intestines—the gut microbiome, which plays dramatic roles in human health and development.

The power to extract personal data from eDNA and microbiome samples will continue to increase, both groups of authors warn. That raises concerns about misuse by police or other government agencies, collection by commercial companies, or even mass genetic surveillance, says Natalie Ram, a law and bioethics scholar at the University of Maryland Francis King Carey School of Law. In the United States, she says, researchers and funding agencies should make greater use of federal Certificates of Confidentiality. They prohibit the disclosure of “identifiable, sensitive research information” to anyone not connected with a study, such as law enforcement, without the subject’s consent….

“Which companies and governments are going to pay and license to have poop-based surveillance technology?” he asks. “Imputing people’s identity based on their poop is compelling and interesting, for a number of reasons, and most of them are all the wrong reasons.”

Excerpts from Gretchen Vogel, Privacy concerns sparked by human DNA accidentally collected in studies of other Species, Science, May 15, 2023