Cell phone science: Can the molecules you leave behind determine who you are?

cellphonedial_cropHumans leave behind trace chemicals, molecules and microbes on every object we touch. By sampling the molecules on cell phones — an object we tend to spend a lot of time touching — researchers conducting a recent study were able to construct lifestyle sketches for each phone’s owner, including diet, preferred hygiene products, health status and locations visited.

It all started with a 2015 study in which Dr. Pieter Dorrestein, a professor at the University of California San Diego School of Medicine, and his team constructed 3D models to illustrate the molecules and microbes found at hundreds of locations on the bodies of two healthy adult volunteers. Despite a three-day moratorium on personal hygiene products before the samples were collected, the researchers were surprised to find that the most abundant molecular features in the skin swabs still came from hygiene and beauty products, such as sunscreen.

“All of these chemical traces on our bodies can transfer to objects,” Dorrestein said in the article. “So we realized we could probably come up with a profile of a person’s lifestyle based on chemistries we can detect on objects they frequently use.”

Published in the Proceedings of the National Academy of Sciences, the article explains studies like this one could have a number of applications, including criminal profiling, airport screening, medication adherence monitoring, clinical trial participant stratification and environmental exposure studies, just to name a few.

In Dorrestein’s latest study, 39 healthy adult volunteers participated. The team swabbed four spots on each person’s cell phone and eight spots on each person’s right hand, for a total of nearly 500 samples. Then, they used a technique called mass spectrometry to detect molecules from the samples.

The article explains the team identified as many molecules as possible by comparing them to reference structures in the GNPS database, a crowdsourced mass spectrometry knowledge repository and annotation website developed by Dorrestein and study co-author Dr. Nuno Bandeira.

With this information, the researchers developed a personalized lifestyle “read-out” from each phone. Some of the medications they detected on phones included anti-inflammatory and anti-fungal skin creams, hair loss treatments, anti-depressants and eye drops. Food molecules included citrus, caffeine, herbs and spices. Sunscreen ingredients and DEET mosquito repellent were detected on phones even months after they had last been used by the phone owners, suggesting these objects can provide long-term composite lifestyle sketches.

“By analyzing the molecules they’ve left behind on their phones, we could tell if a person is likely female, uses high-end cosmetics, dyes her hair, drinks coffee, prefers beer over wine, likes spicy food, is being treated for depression, wears sunscreen and bug spray — and therefore likely spends a lot of time outdoors — all kinds of things,” author Dr. Amina Bouslimani said. “This is the kind of information that could help an investigator narrow down the search for an object’s owner.”

There are limitations, however. First of all, these molecular read-outs provide a general profile of person’s lifestyle, but they are not meant to be a one-to-one match, like a fingerprint. To develop more precise profiles and for this method to be more useful, he said more molecules are needed in the reference database, particularly for the most common foods people eat, clothing materials, carpets, wall paints and anything else people come into contact with. He’d like to see a trace molecule database on the scale of the fingerprint database, but it’s a large-scale effort that no single lab will be able to do alone.

Moving forward, the researchers have already begun extending their study with an additional 80 people and samples from other personal objects, such as wallets and keys. They also hope to soon begin gathering another layer of information from each sample — identities of the many bacteria and other microbes that cover our skin and objects.

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