The method draws on an understanding that the outermost layer of human skin carries chemical components drastically affected by the body’s inner chemistry and external, environmental factors. Researchers were able to capture the skin molecules present on these personal items and match them to a vast array of environmental and biological factors, quickly processing and crosschecking databases using a supercomputer.
Some of the molecules found on phone surfaces had lingered for extended periods of time. Researchers found traces of DEET on one participant’s phone even though that person had applied the mosquito repellent nearly five months before the study.
Pieter Dorrestein and Amina Bouslimani, co-authors of the study, decided to use phones to collect samples because of their widespread use. “We thought about what objects that we most frequently interact with that has the highest chance of demonstrating our proof of principle, that so much could be determined from a sample of these molecules,” Dorrestein said. “The phone is very obvious. Most of us spend so much time on our phones, so there are lots of molecules from your hands being transferred to the object itself at all times.”
Dorrestein and Bouslimani think that the applications of this type of broad chemical analysis are vast. They cited possible medical applications that monitor the effect of medication on a patient. The effects of using cosmetics and skin-care products can also be monitored. They also mentioned potential law enforcement uses, where officials could analyze samples from phones, car keys, handbags or other personal items left at a crime scene to determine the profile of a suspect.
But just how different is this method from other means of collecting chemical data? For example, medication effectiveness can be measured through blood samples. On the law enforcement side, police officers already have access to forensic analysis tools that can determine the presence of illegal drugs or explosives on objects found at crime scenes, and the addition of lifestyle information might not be particularly useful to narrowing down a subject. “The problem is [these lifestyle profiles] are not very discriminating things — if you were to find a particular brand of cosmetic it is not really going to narrow down for you who you would be looking for,” said John Bond, an associate professor in criminology at the University of Leicester in an interview with the Guardian.
But Dorrestein claims that the full profile of information gleaned from these samples, rather than targeted analysis of traces of illegal drugs, for example, makes the methodology useful to law enforcement. “The hardware that is used are not any different than what the FBI uses,” Dorrestein said. “It’s the thought process of the data that comes out. We can learn more from this swab than just an illicit molecule from this information. We can actually learn about the lifestyle of an individual.”