Tracking You By Your Hair

Your body contains a lot of tracking and recording devices. Anything that grows reasonably slowly — your hair, and I suspect also your fingernails or toenails — embeds bits of whatever was in your body at the time a given millimeter of the hair was being formed. Analyzing hair to determine recent drug use has been around for a while — the idea being if you’ve smoked or taken anything in the last few months (or years), it will show up at the appropriate point in strands of your hair.

These scientists have taken the idea a little further. They’ve mapped the relative concentration of different hydrogen and oxygen isotopes in water supplies around the world. Since even bottled drinks tend to be bottled locally, they can look for those isotopes in a hair sample and determine approximately where someone’s been from their hair.

The somewhat scary aspect of this is that the technical expertise needed to do it is comparatively low. The main hurdle is manpower and time — getting hair samples from enough different areas of the world.

Somehow I’m reminded of long rows of glass jars with yellow cloths in…

“2,000 envelopes and vials stored here also contain human hair, collected from across the United States and around the world. “Guatemala, Japan, Newfoundland, Thailand,” says Valenzuela, rattling off some of the countries.
In fact, the scientists have hair from every continent, even Antarctica. They are using all this hair—from regular, everyday people—to perfect a technique to help solve murder cases.[…]

Ehleringer realized that what an animal eats and drinks does get recorded—in its tissues.

Every chemical element comes in different forms, known as isotopes, with some slightly heavier than others. Take hydrogen and oxygen, the atoms that make up water, H2O. Their different isotopes are found in different concentrations depending on where the water comes from. And that mixture of heavy and light atoms gets laid down in the growing tissues of the animals that drink the water. These tissues include hair.

“The hair becomes a linear tape recorder,” says Ehleringer. “So it tells us a little story about the history of what an animal was eating or drinking.”

Our hair acts as a timeline—recording where each of us has been and when we were there.Ehleringer suspected the same thing would apply to humans and our hair. So he and his colleagues collected hair from local barbershops across the U.S. to test a hypothesis. They wanted to determine if it was possible to tell where hair came from based on an analysis of the hydrogen and oxygen in the local water supply.

Thure Cerling, a geologist at the University of Utah and another collaborator on this project, says the vast majority of the water in our diet is local.

“People often say, ‘Well, oh, I don’t drink water. I drink Coke,'” he says. “[But] where was the Coke or the Pepsi bottled?” It’s usually at a local bottling plant, using local water.[…]

At about the same time that the Utah scientists were developing this technique, a team in the United Kingdom was working on the same approach.

Wolfram Meier-Augenstein, a chemist at the James Hutton Institute in Scotland, has examined the isotopic composition of hair and water in Europe and the Middle East, and he has used that information to help police in the U.K., United Arab Emirates, and elsewhere with about a dozen murder cases.

He is not at liberty to talk about most of those cases, but in one case he can discuss, a man was found dead in Wales several years ago. The man appeared to be Asian, but police did not know where he came from or when he entered the U.K.

The man’s hair was almost six inches long. Meier-Augenstein explains that was long enough to determine where the man had lived in the year before he died.

“The person lived in the Ukraine for three months, moved then to Germany for six-and-a-half months, and then to the United Kingdom prior to his untimely death,” he says.

The police knew of an organized crime gang that was shuttling illegal Vietnamese immigrants into Britain via Ukraine and Germany. The police suspected the murder victim had been smuggled into the U.K. by that gang.

By examining isotopes in hair, scientists can also learn other things about a person diet—including whether someone was vegetarian or vegan, preferred fish to chicken or beef, or had gone through an sustained period of starvation.Once the clue from the hair analysis had confirmed that suspicion, the other bits of the puzzle came together. The police learned that the man was originally from Vietnam and had been killed in a dispute over marijuana.

“In any homicide investigation, knowing who the victim is, is critical—who they associate with, where they’ve been,” says John House, head of the criminal investigative division at the Royal Newfoundland Constabulary, in Canada.

House has used this type of forensic analysis of hair and says it can offer a starting point for murder cases that would otherwise go cold fast. “Without that information, we’re really at a standstill,” he says.

By examining isotopes in hair, scientists can also learn other things about a person’s diet—including whether someone was a vegetarian or vegan, preferred fish to chicken or beef, or had gone through a sustained period of starvation. All of these details might prove helpful in identifying a murder victim.

Back in Salt Lake City, Luciano Valenzuela pulverizes a hair sample in a machine that looks like a small version of a paint can shaker. This is one of the first steps the staff at IsoForensics uses to analyze hair isotopes.


The company gets requests from law enforcement agencies once or twice a month, and the demand is growing. Meanwhile, the scientists continue to refine the technique by gathering more hair from other parts of the world.

“Obviously, everywhere we go and every time we get a chance, we continue to collect samples,” says Lesley Chesson.

She looks over at Valenzuela, who is from Argentina. “Luciano,” she says, smiling, “maybe we should send you home for Christmas—send you on a collecting trip.” They both laugh.

That chance will come soon enough. Valenzuela returns to Argentina next year to start his own lab. His goal is to create a detailed map of the invisible variations in hair and water across his own country.”


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