- A professor at the University at Albany has come up with a new way to determine blood alcohol concentration through sweat analysis.
- Jan Halámek, the forensic chemist whose lab came up with the new process, says that because sweat glands are positioned closely to circulating blood, some ethanol is actually passed to our sweat.
- In the past, Halámek has come up with other clever uses for sweat, including as a biometric for unlocking phones.
Sure, sweat stinks, but it’s actually a fascinating body liquid because it works as a biometric. As in, don’t leave your sweaty fingerprints at a crime scene and don’t be surprised if breathalyzers are replaced with sweatalyzers in the near future.
Jan Halámek, an assistant professor of chemistry at the University at Albany, works as a forensic chemist and has a fully dedicated lab at the college. There, he and his students have uncovered something pretty wild: Your perspiration can totally give you away if you’ve been pulled over for drunk driving. The research was published last month in the scientific journal Analytical Chemistry.
Because sweat glands are positioned closely enough to circulating blood, some of the ethanol that courses through your veins after you have a beer or two will be transferred to the sweat. That makes it possible to measure how much ethanol is in the blood through sweat analysis.
“You smell that? You smell that? Sure, it’s on your breath, but it also comes through the perspiration,” Halámek tells Popular Mechanics. That’s why it’s so easy to tell if someone’s been drinking through your sense of smell alone.
Testing the Sweat
Halámek and his lab are in the process of creating a test strip that can determine those alcohol levels in the blood through sweat. The scientists have an active prototype ready, but they’re in the process of engineering a final product that could be used commercially. It would work a bit like a glucometer or pregnancy test, he says.
When the strip is placed against the skin of a suspected intoxicated individual, any ethanol present produces a visible color spot after 60 to 90 seconds. The darker the color spot, the more alcohol in the system, Halámek says. There is a significant delay in ethanol reaching the sweat, however. Halámek says it takes about 10 to 15 minutes for the ethanol to transfer from the blood to the sweat as it’s metabolized.
“The ethanol goes through the stomach and then goes through the blood,” he says. “From blood, it will transfer through to the tissues because [ethanol] is a small molecule.”
That’s not a huge drawback for this technology, though, because breathalyzers also have a sort of delay. Say you just took a shot of vodka. Your blood alcohol concentration (BAC) is going to spike because the ethanol has just entered your stomach and has not yet been metabolized. Your reading on a breathalyzer is going to be much higher than it would be in another 10 minutes, says Halámek.
It might actually be more beneficial to use a sweat strip to test the levels of ethanol in your system rather than a breathalyzer, he says, because those behind the wheel can use the excuse that they’ve just used mouthwash. Plus, people with diabetes actually tend to have acetone, another type of alcohol, on their breath. That’s thanks to ketosis, the same body process that breaks down fatty acids for energy. While the fat is broken down, your breath can smell sweeter thanks to the release of ketones, including acetone, as a byproduct.
Since people are constantly sweating—all over the body, all the time (watch this video of a finger sweating for proof)—you can pretty much always get a reading, even if a person is unconscious, says Halámek. That’s opposed to a breathalyzer test, which can require a blow of up to 10 seconds.
Plus, you only need the tiniest amount of sweat to conduct one of these sweat analysis tests—as in, less than a drop, which is less than one microliter, a.k.a one millionth of a liter.
To test out his sweat strip concept, Halámek’s lab led a controlled drinking study with 26 volunteers. Each individual first provided a sweat sample that proved their sobriety, then they took a few shots of 40 percent vodka until their BAC hit 0.08 percent. Then, over the next few hours, the lab took more than 100 readings on the sweat strips and breathalyzers. There was a strong correlation between the results.
Halámek and company are working with the University at Albany’s computer science department to design a smartphone app that will work with the sweat strips. The idea is to align the sweat strip’s color change with BAC to avoid any discrepancies.
Unlocking Sweat Potential
This isn’t the first time Halámek, who earned his Ph.D. in biochemistry from Masaryk University in the Czech Republic, has used sweat to solve a problem. Two years ago, he published a paper in the scientific journal ChemPhysChem on a sweat identification system that would work a bit like a fingerprint scan to unlock a phone—but, you guessed it, with a sweat profile.
Your sweat has its own unique signature, kind of like a fingerprint or sample of saliva, Halámek says. It’s influenced by what you put into your body, but remains relatively stable across days (unless you’re sick or pregnant, that is). Our signatures are all different, then, because we have varied amounts of active metabolites in our sweat.
“None of us is eating the same food or drinking the same drinks,” Halámek says. “There’s little chance that my lactate level and your lactate level are the same.”
The idea is to build an amino acid profile. These molecular building blocks are found in sweat and “can be exploited for the establishment of an amino acid profile capable of identifying an individual user,” according to the paper.
To build a profile, a device would first conduct a monitoring period where it could continuously measure the user’s sweat across various times of the day. Those who work the night shift, for example, will have a different sweat profile at 2 a.m. than those who work day shifts and are in bed by that time. Once that profile is created and saved, the device’s owner can be identified simply by holding the phone.
Currently, Halámek is working with engineers to build a device that can handle this process. Meanwhile, we’ll be patiently waiting to see how a company like Apple might one day use and market this idea: SweatID, anyone?