Chemicals in hair care products cause surprising amount of health issues

Recent research from Purdue University highlights a concerning aspect of many Americans’ daily routines: the inhalation of potentially harmful chemicals during hair care. The study led by Assistant Professor Nusrat Jung from the Lyles School of Civil Engineering sheds light on the significant emissions of volatile chemical mixtures from everyday hair care products.

Chemical exposure in daily routines

Jung’s team discovered that during a single hair care session, an individual could inhale between 1 and 17 milligrams of harmful chemicals. The primary concern centers around cyclic volatile methyl siloxanes, commonly found in hair care products.

“We found the results to be extremely alarming,” Jung said. “We did not expect to see such significant emissions of volatile chemical mixtures from off-the-shelf hair care products during typical hair care routines that many people perform each and every day.”

D5 siloxane chemicals in hair products

The study particularly highlights the dangers of D5 siloxane, an organosilicon compound prevalent in many hair care products. According to Jung, this compound, already restricted in the European Union, poses risks to the respiratory tract, liver, and nervous system based on animal studies.

“D5 siloxane has been found to lead to adverse effects on the respiratory tract, liver and nervous system of laboratory animals,” Jung said. “The use of the chemical in wash-off cosmetic products has already been restricted in the European Union because of this. Many of these products are scented, too, and some of the chemicals used to make these fragrances are potentially dangerous to inhale as well.”

The European Chemicals Agency classifies it as “very persistent, very bioaccumulative,” raising concerns about its long-term human impact.

“There has not been much in-depth research into this, so we really have no idea to what extent the threat these chemicals pose when inhaled over a long period of time,” Jung said. “There have been tests into ‘wash-off’ products like shampoos, but almost none for ‘leave-on’ products like hair gels, oils, creams, waxes and sprays.”

Heat and hair care chemicals

Applying heat to hair care products, such as with curling irons and hair straighteners, significantly increases chemical emissions. The research found that at 210 degrees Celsius, emissions increased by 50% to 310%.

Jung’s research also indicates that these chemicals don’t remain confined to a single room but can spread through urban environments via home ventilation systems. This widespread dispersion affects even those who don’t use such products.

“Home ventilation is likely a major pathway of indoor-to-outdoor siloxane transport,” Jung said. “In urban environments, this is especially significant as you will have hundreds — even thousands — of homes ventilating out potentially harmful chemicals into the urban atmosphere all in a short span of time as people get ready for work and school in the morning. These chemicals are then collectively piped back into buildings through ventilation systems once more. So even if using products with harmful chemicals is not part of your hair care routine, you will still be impacted due to your surroundings in an urban environment.”

The study also reports that 16% to 70% of surveyed individuals use leave-on hair care products. Based on average usage patterns, the estimated annual emission of D5 in the U.S. could range from 0.4 to 6 metric tons.

“There’s a good reason why these chemicals are restricted from being used in wash-off hair care products in certain parts of the world,” Jung said. “The effects on people and the planet need to be studied further and regulatory action needs to be taken.”

Recommendations and precautions

Jung advises the best protection is to avoid these products altogether. If usage is necessary, Purdue civil engineering PhD student Jinglin Jiang suggests using exhaust fans to reduce inhalation exposures, which can be effective but also contributes to environmental impact.

“Ventilation can be an effective way to reduce siloxane exposures during indoor hair care routines,” Jiang said. “Our model shows that turning on the bathroom exhaust fan can reduce D5 inhalation exposures by over 90%.”

Jung further emphasizes the need for more in-depth research and regulatory action, considering the potential effects on human health and the environment.

“The best solution is to simply not use these products,” Jung said. “I used to use similar products myself to straighten my hair, but after we analyzed the data, it became immediately clear that the best thing I could do to protect my own health was to stop using them.”

Studying hair care chemicals

The experiments were conducted in the Purdue zero Energy Design Guidance for Engineers (zEDGE) Tiny House, a mechanically ventilated, single-zone residential building. Using a high-end proton-transfer-reaction time-of-flight mass spectrometer, the team measured volatile chemicals in real-time.

The study included three types of experiments: realistic hair care routines, hot plate emission tests, and surface area emission studies. Participants used their own products and tools, replicating their routines in the zEDGE environment. The focus was on indoor volatile organic compound concentrations and emissions during and after the hair care activities.

In summary, the Purdue University study highlights a critical yet overlooked aspect of daily life: the potential health risks associated with common hair care products. The findings call for increased awareness, further research, and regulatory measures to mitigate these hidden dangers.

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

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