That 20-minute hairstyling session with your flat iron just pumped billions of toxic nanoparticles into the air around your face, creating pollution levels that rival standing behind a city bus during rush hour, according to a new study.
The study findings highlight the need to rethink air quality regulation and product safety, Nusrat Jung, lead author and assistant professor at Purdue University’s Lyles School of Civil and Construction Engineering, told The Epoch Times.
“The combination of heat and certain ingredients is clearly a recipe for airborne nanoparticle formation, raising concerns about a wider range of hair treatments and products,” he said.
What Goes Into a Good Hair Day
Styling hair with hair products creates air pollution that is comparable to traffic exhaust and cooking fumes.
In a test-house lab designed to track indoor air, researchers recreated everyday styling routines. Seven volunteers used curlers, straighteners, and wavers with popular creams, serums, lotions, and sprays, while the team adjusted for heat, hair length, and ventilation. Monitors tracked the surge of particles and vapors in real time. Then, with computer modeling, the researchers traced where those invisible particles would likely travel—down the nose and throat, or deep into the lungs.
Using hair products with heated tools causes the rapid release of billions of nanoparticles, concentrating at tens of thousands to hundreds of thousands of particles per cubic centimeter, according to a new study in Environmental Science & Technology.
“This close proximity and confinement give airborne nanoparticles a more direct pathway into the lungs, and the doses can be surprisingly high even during a short styling routine,” Jung said.
Most people style their hair in bathrooms with poor ventilation, allowing particle concentrations to build up rapidly. Unlike outdoor pollution that gets diluted by wind and space, these particles have nowhere to go, Aidan Charron, associate director of Global Earth Day, who wasn’t part of the study, told The Epoch Times.
Heating Increased Particle Release
Ingredients in hair products are not typically airborne at room temperature but vaporize when heated, forming nanoparticles, which are invisible to the naked eye.
Airborne nanoparticles can be harmful to health by penetrating a person’s lungs, causing biological reactions such as oxidative stress. While they have not been directly tied to health damage, prolonged exposure has been linked to lung stress.
Further heating—to around 360 degrees Fahrenheit—can cause these nanoparticles to form smaller ultrafine particles. These microscopic particles are more harmful than larger nanoparticles as they can penetrate deep into the lungs, stick to airway surfaces, and enter into the air sacs.
Inside air sacs, ultrafine particles can trigger inflammation and, in some cases, pass into the bloodstream and reach other organs. By contrast, larger particles stick in the larger airways or nose and throat, where many can be cleared out by coughing, sneezing, or mucus.
Research suggests these particles may contribute to acute effects such as breathing irritation, and chronic risks such as asthma or cardiovascular problems, with long-term exposure.
“It takes a lot of chemicals to make your hair smell like coconut and apple,” Charron said.
The main chemicals given off from hairstyling are siloxanes.
D4, D5, and D6—collectively known as cyclic siloxanes—are widely used in hair products and cosmetics. They act as emollients and conditioners, giving products a silky, nongreasy feel. They keep hair manageable, reduce frizz, and add shine without buildup.
D5 and D6 have been banned in the EU due to concerns about their persistence and accumulation in the human body, with animal studies showing that this can cause lung inflammation and liver damage at high doses. However, they are not banned in the United States. An independent review by the U.S. Food and Drug Administration concluded that cyclic siloxanes are safe at current levels.
Similarly, a Canadian government risk assessment found that, at levels of consumer exposure, D5 and D6 are not harmful to human health or the environment.
A Call for Better Regulation
In the United States, the FDA does not review or approve cosmetic ingredients before they hit the shelves—except for color additives. Instead, companies are held legally responsible for ensuring their products are safe under the Federal Food, Drug, and Cosmetic Act.
While the agency’s independent review concluded that cyclic siloxanes are safe at current usage levels, critics point out that safety reviews often focus on short-term consumer use—overlooking occupational exposures, environmental impacts, and long-term risks.
Meanwhile, the Environmental Protection Agency is conducting a separate formal risk evaluation of cyclic siloxanes, examining environmental fate, indoor and outdoor air exposure, and bioaccumulation concerns.
Experts recommend several strategies to reduce your exposure:
- Avoid the Problem Entirely: Switch to heat-free styling methods when possible, or skip styling products that contain siloxanes.
- Improve Ventilation: Use exhaust fans, open windows, or style your hair in well-ventilated areas rather than small bathrooms.
- Choose Safer Products: Look for siloxane-free formulations and products with shorter, more recognizable ingredient lists.
- Read Labels Carefully: Avoid products listing D4, D5, or D6 siloxanes, especially if you use high-heat tools.