Heat-based hair styling found to produce lung-penetrating pollution

Research has found that a typical 10–20 minute morning hair care routine using heated styling tools with everyday hair products can release over 10 billion nanoparticles that deposit directly into the lungs. According to the researchers, the findings raise concerns about the practice’s long-term health effects.

The Purdue University study, published in Environmental Science & Technology, says the airborne nanoparticle exposure level is identical to that of standing in heavy highway traffic.

The US-based research team documented that the particles, many of which are smaller than 100 nanometers, are linked to risks such as respiratory stress, lung inflammation, and even cognitive decline.

“The sheer number of nanoparticles released from everyday hair care products was far greater than we ever expected,” assistant professor Nusrat Jung, tells Personal Care Insights. 

“Our modeling showed that during a single styling session, more than 10 billion of these nanoparticles could deposit in the respiratory system, with most reaching the deepest part of the lungs (pulmonary region),” she explains, adding that this was “one of the most concerning” findings of the study.

She stresses that the findings point to a need for manufacturers to rethink formulations and develop products that do not generate harmful nanoparticles when used with heat.

Measuring indoor emissions

The research was conducted in a controlled residential laboratory, part of Purdue’s Engineering test houses. Participants replicated their typical hair styling routines using products such as creams, serums, sprays, and heated tools, including straighteners, curlers, and wavers.

To capture emissions in real time, the team used advanced aerosol instrumentation to measure nanoparticles between six and 500 nanometers, and a proton transfer reaction time-of-flight mass spectrometer to track volatile organic compounds. Ventilation levels were also adjusted to mimic real household conditions.

The researchers tested variations such as hair length, product type, appliance surface temperature, and airflow.

The researchers tested variations such as hair length, product type, appliance surface temperature, and airflow.Participants applied their chosen products and styled each hair section while instruments monitored air quality second by second. This was followed by a 60-minute decay period to assess how long pollutants lingered indoors.

Health impact assessment

The findings showed that temperature was the key driver of emissions. Styling at surface temperatures above 148 °C produced nanoparticle concentrations of 10,000 to over 100,000 particles per cubic centimeter. More than 95% of these particles were below 100 nanometers in size.

“Hair styling tools aren’t all equal when it comes to the nanoparticles they release. Straighteners consistently produced the most nanoparticles, far more than curlers or wavers, even when used at the same heat settings,” Jung notes.

She adds that increasing the temperature worsened the nanoparticle exposure: “High heat released dramatically more particles than low heat or no heat at all.”

“Hair length mattered too: styling long hair generated much higher exposures than short hair under the same conditions.”

Chemical drivers

Chemical analysis revealed that cyclic siloxanes were a significant source of these particles. Siloxanes are commonly used in hair sprays, gels, and creams for their smooth texture and heat resistance.

When exposed to high heat, these compounds volatilize and nucleate into airborne nanoparticles. Some secondary formation also occurred through the reaction of fragrance additives with ozone.

“Siloxanes have been found to lead to adverse effects on the respiratory tract, liver, and nervous system of laboratory animals,” Jung explains.

“In the short term, breathing [the particles] in can irritate the lungs and worsen conditions like asthma. Over time, there is potential for more serious impacts because nanoparticles can pass from the lungs into the bloodstream, spreading to other organs.” 

Straighteners consistently produced the most nanoparticles, far more than curlers or wavers.“Research links long-term exposure to these kinds of particles with chronic respiratory and heart disease, and possibly effects on the brain. This makes even routine styling a source of invisible air pollution that could have lasting health implications,” she emphasizes.

Toward safer hair care

The authors concluded that heat-based hair styling should be recognized as a significant indoor source of nanoparticle pollution. This adds to the growing body of evidence on indoor air quality risks from personal care routines.

They suggest that improved ventilation or reducing the use of heated products can help minimize exposure.

The researchers also call for improved transparency between personal care companies and consumers.

“Greater transparency in ingredient lists and targeted innovation toward safer alternatives could significantly reduce exposure,” Jung concludes. “Our findings show that the beauty and cosmetic industry has an opportunity and a responsibility to make everyday styling products safer for those who use them.”