A Reddit post made a major splash on the internet this week when it claimed that the infamous, $30 “GamerGirl bathwater” being sold by social media star Belle Delphine contained no human DNA — and therefore might not be her bathwater at all. This was promptly challenged by other Reddit users and debunked: the shipments of said bathwater hadn’t even been sent out yet. As the news of the non-scandal broke around The Verge offices, reporters began pelting the science desk with questions, including; “wait, you can test bathwater for DNA?”
“Yes, you can,” says forensic biologist Helen Page. Page is a senior lecturer at Teesside University in the UK, and has actually studied how to recover very specific samples of DNA from a bath.
It’s serious work. Recovering DNA from a shower or bath can be useful during the investigation of a sexual assault, especially if a victim doesn’t want to undergo a full forensic exam, or showered after the assault. Page has studied how semen can be recovered from specially-designed mesh objects made to fit in shower drains, and “bath scrunchies” (also known as sponges, loofahs, or poufs). She found that you can recover DNA from mesh, from scrunchies, and also by simply wiping around the walls, base, and drain of a tub.
Page has shown it’s possible to recover DNA from semen in bathwater, but semen is very different from other cells. “The structure of a sperm is quite resistant, as it were, to degradation in the same way that other cells would be,” Page says. In the case of Delphine, the most likely source of DNA would be skin that might get sloughed off in the tub. Page’s research was also done under controlled conditions in the lab. In the case of the “GamerGirl Bathwater,” without seeing the manufacturing process, there’s really no way to know how much of Delphine’s DNA made it into the water at all.
“It’s hard to know how many cells would have been shed in the process of washing,” Page says. She points out that if Delphine washed lightly, fewer skin cells would come off than if she washed more thoroughly. “I very much doubt there’s going to be a huge quantity of DNA in a small vial of the bathwater,” Page says.
It’s not clear how long DNA would last in bathwater, either. The biggest threats to DNA’s integrity are heat, humidity, and bacteria, which tubs have in abundance. Soap and other cleaning products might also play a role in breaking down DNA, but there’s not enough scientific research available to know for sure.
Even if there is enough DNA in the water to test, and you had the right lab equipment, and it hasn’t degraded, all an analysis could tell a person is whether or not the DNA is human, not which human was bathing in it. “You wouldn’t be able to tell it was her DNA unless you had her DNA profile to compare against.” Page says.
Of course, all of this only answers the question of whether people could — not whether they should — test a small jar of $30 bathwater for DNA in the first place. Why it’s being sold, however, is crystal clear: as Patricia Hernandez points out at Polygon, Delphine is known for performance-art-worthy stunts.
While Page emphasizes that she wouldn’t spend her money on bathwater, she does understand why people might want to authenticate their purchase. “If I was paying that much money for some water that had been bathed in by Person X,” Page says, “then I’d want the bathwater to have been bathed in by Person X.”
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