Environment Your DNA can now be pulled from thin air. Privacy experts are worried. Technology focused on eDNA, a Harvard researcher 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. Environmental DNA research has aided conservation, but scientists say its ability to glean information about human populations and individuals poses dangers. Isabel Seliger/The New York Times 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…