Hair styling releases billions of toxic nanoparticles that then enter your body

Many of us associate air pollution with traffic, industry, or outdoor smog. Yet daily personal care routines can expose people to invisible risks within their own homes.

Hair sprays, serums, and heat styling tools release particles so tiny they can slip deep into the lungs. New research reveals just how significant these exposures may be.

Billions of tiny particles

A Purdue University team led by Nusrat Jung and Ph.D. student Jianghui Liu found that a 10-20 minute hair styling routine can produce more than 10 billion airborne nanoparticles.

These particles are smaller than 100 nanometers and can penetrate deeply into the lungs, triggering respiratory stress, inflammation, and even cognitive effects.

“This is really quite concerning,” Jung said. “The number of nanoparticles inhaled from using typical, store-bought hair-care products was far greater than we ever anticipated.”

Heat drives the release

The study shows that heating tools like straighteners or curlers are the primary drivers of nanoparticle release.

At temperatures above 300 degrees Fahrenheit, volatile and low-volatility chemicals rapidly evaporate, nucleate, and condense into dense clouds of particles.

At 360 degrees and higher, sub-100 nanometer particles made up more than 95 percent of the emissions.

“Atmospheric nanoparticle formation was especially responsive to these heat applications,” Liu explained. “Heat is the main driver – cyclic siloxanes and other low-volatility ingredients volatilize, nucleate and grow into new nanoparticles, most of them smaller than 100 nanometers.”

Harmful hair styling chemicals

Among the chemicals, D5 siloxane stands out. This ingredient is widespread in hair products because of its smooth texture and thermal stability.

Yet it is very persistent in the environment and bioaccumulates in living organisms. Animal studies link D5 siloxane to respiratory, liver, and nervous system damage.

“When we first studied the emissions from hair care products during heat surges, we focused on the volatile chemicals that were released, and what we found was already quite concerning,” Jung said.

“But when we took an even closer look with aerosol instrumentation typically used to measure tailpipe exhaust, we discovered that these chemicals were generating bursts of anywhere from 10,000 to 100,000 nanoparticles per cubic centimeter.”

More than one pathway

The Purdue study revealed that two mechanisms fuel nanoparticle creation. The first is volatilization of siloxanes and similar ingredients during heating.

The second involves atmospheric chemistry: fragrance additives and terpenes can react with indoor ozone, producing secondary organic aerosols.

Even when no heat was applied, some nanoparticle formation still occurred through these chemical reactions.

Breathing zone risks

Hair styling often happens close to the face, placing emissions directly in the breathing zone. Modeling shows that nanoparticles deposit most efficiently in the pulmonary region, the deepest part of the lungs.

Pulmonary deposition rates for sub-100 nanometer particles are especially high, raising concern over repeated exposures from daily routines.

Hair styling products and tools matter

The researchers found that temperature mattered more than product type. At 410 °F, more than 46 billion nanoparticles deposited in the respiratory system, compared to less than one billion at 300 °F.

Long hair also led to higher doses, since longer styling times produced more emissions.

Interestingly, appliances behaved differently. Straighteners and curlers emitted the most ultrafine particles, while wavers generated fewer but larger particles.

Even so, larger particles can carry greater mass, meaning risk cannot be judged by particle counts alone.

Safer hair styling practices

For context, 20 minutes of hair straightening at high heat can equal the nanoparticle dose of 20-200 minutes of sitting in vehicle traffic or 30-100 minutes of exposure to urban outdoor air.

In poorly ventilated homes, these exposures can become even higher as particles linger longer in indoor air.

Jung and Liu recommend limiting the combined use of hair products and heat tools. If use cannot be avoided, ventilation becomes essential. Exhaust fans, open windows, or air purifiers can help reduce particle buildup.

“If you must use hair care products, limit their use and ensure the space is well ventilated,” Liu said. “Even without heating appliances, better ventilation can reduce exposure to volatile chemicals, such as D5 siloxane, in these products.”

Future research directions

Future studies aim to measure even smaller particles down to one nanometer and identify their chemical makeup. This will help clarify the full health implications of these emissions and refine strategies to reduce risks.

“By addressing these research gaps, future studies can provide a more holistic understanding of the emissions and exposures associated with heat-based hair styling, contributing to improved indoor air pollution assessments and mitigation strategies,” Jung said.

The study is published in the journal Environmental Science & Technology.

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