Beware Hair Care: It Might be Safer to Leave Your Head Bare
Tell me if this sounds familiar: you’re just trying to look hot by applying some HCP in your homey little zEDGE, but suddenly the PTR-TOF-MS picks up crazy ERs of cVMS and monoterpenes and suddenly you’re worried about massive indoor-to-outdoor transport of VOCs that might, I don’t know, give your neighbors cancer. So frustrating, right?
WTF?!?
Okay, yeah, so. Here’s the deal. Hair lotions, creams, pomades, oils, shampoos, conditioners, serums, masks, and sprays are typically made from the kind of syllable-salad that comes from piling in dozens of custom-manufactured chemicals.
The chemicals are in there because they help the products stay smooth and creamy at room temperature or more evenly distribute specific oils over our hair. But after they do their job, they don’t just disappear—they can linger on our skin, potentially being absorbed, or (more often) they can evaporate into the air where they linger, waiting to be breathed in.
That isn’t necessarily a problem—some of these chemicals are harmless. Others, not so much. One potentially risky category is “siloxanes,” a group of silicone-based ingredients that are used in tens of thousands of hair care and cosmetic products all over the world. They’re currently categorized as safe for consumers, at least in Europe, although one of them (“D4”) is currently being reviewed by the EPA here in the US. There’s some solid evidence, though, that they might lead to cancer risk and/or issues with lung and kidney function.
A big part of why they’re still legal is that they tend to evaporate pretty quickly, and the products that have the most siloxanes in them, like shampoo, tend to be stuff that we wash off (that can be a problem for fish, but we’re focused on humans right now).
The problem is that, until a few months ago, no one had checked whether evaporating creams, pomades, oils, and so on might release siloxanes into our bathrooms and bedrooms as we apply them, potentially in such high amounts that they could actually be dangerous.
The Experiment
Enter Jinglin Jiang and her team out of Purdue. They put together an experiment using some cutting edge tech—a sealed and ventilated tiny house (the “zEDGE”) and a high-resolution, time-sensitive mass spectrometer to measure concentrations of chemicals in the air (that’s the “PTR-TOF-MS”) with a special focus on potentially dangerous siloxanes.
Then they brought people in to do their normal hair-care routines, using their normal products from home, and carefully separated out chemicals from the tiny house itself, chemicals released or carried in by the participants, and chemicals that came specifically from the hair care products (HCPs).
The results are concerning. Cyclic volatile methyl siloxanes, or cVMS, were measured at much higher-than-normal concentrations in the tiny house during people’s hair care routines. Two factors dramatically changed how much cVMS they inhaled: whether the exhaust fan was on, and whether they used heated tools like hair straighteners.
It took about 20 minutes for the chemicals to dissipate. During that time, participants absorbed anywhere from 1 to 20 mg of the most common siloxane, decamethylcyclopentasiloxane (D5). Over a year, they calculated that daily use of a hair care product with these chemicals in it would end up putting anywhere from 4 g to 65 g of D5 into our bodies, depending on whether the fan was on or off.
That’s about the weight of a C battery. A battery’s worth of a potentially deadly chemical every year.
Plus, there’s a twist. Having the exhaust fan on is a must for the safety of the person using these products, but all that really accomplishes is moving D5 from inside to outside. Fan-on, the authors figure daily use would add up to 310 g per year in the area just outside your home—about a soup-can’s worth of toxic chemicals.
The Take-Home
It’s a brilliant study, and it should leave us with two take-home points. The first is that we really, really need some better research on how dangerous siloxanes are, because anybody putting hair creme in every day, especially in an unventilated bathroom, is taking in way more of it than regulators estimated.
The second is that you should probably avoid cVMS if you can. For a lot of men, this shouldn’t be too hard—lots of pomades and hair oils use mostly natural ingredients, and hair curling and straightening aren’t nearly as common for us. But that only covers men and their direct hair care and styling routines. If you’re sharing your hair care space and time with a partner who uses products containing cVMS, you could both have an exposure risk. The hard part is that these chemicals aren’t always easy to spot since their names get pretty crazy, but this guide can help. As always, a solid basic principle is: look for simple, natural ingredients with names you can understand.
