Unseen Hazards Lurking in Your Bathroom: Disturbing Chemical Emissions Unearthed in Common Hair Products

A recent investigation conducted by Purdue University has shed light on a hidden peril within our daily hair care routines. The study has unveiled that individuals are unwittingly exposing themselves to detrimental chemicals, with a particular focus on D5 siloxane, a prevalent component in numerous hair care products. This inadvertent exposure carries undisclosed long-term health ramifications and contributes to environmental contamination, particularly in urban settings. The findings underscore the urgency of either abstaining from such products or implementing ventilation measures to mitigate exposure, emphasizing the imperative need for further research and potential regulatory actions.

In the typical morning rituals of countless Americans lies an inconspicuous threat – the inhalation of several milligrams of potentially harmful chemicals, as disclosed by Purdue University researchers.

As detailed in a recently published article in Environmental Science & Technology, a journal under the American Chemical Society (ACS) umbrella, Nusrat Jung, an assistant professor in the Lyles School of Civil Engineering, has revealed that a variety of chemicals, notably cyclic volatile methyl siloxanes, which are ubiquitous in hair care products, persist in the air after application. On average, Jung’s team has estimated that an individual can inhale an accumulated mass of 1-17 milligrams of these potentially harmful chemicals during a single hair care session at home.

“We found the results to be extremely alarming,” Jung conveyed. “We did not anticipate such significant emissions of volatile chemical compounds from commonly used hair care products during routine grooming practices that many individuals perform daily.”

The primary culprit identified in this concerning scenario is decamethylcyclopentasiloxane, commonly known as D5 siloxane. This organosilicon compound often occupies the top positions in ingredient lists of numerous hair care products, indicating its prevalence. Over the past few decades, it has become a commonplace ingredient in various personal care products due to its low surface tension, inert nature, high thermal stability, and smooth texture.

“D5 siloxane has been linked to adverse effects on the respiratory system, liver, and nervous system in laboratory animals,” Jung emphasized. “Due to these concerns, the use of this chemical in rinse-off cosmetic products has already been restricted in the European Union. Moreover, many scented products contain chemicals that can be potentially hazardous if inhaled.”

The European Chemicals Agency classifies D5 siloxane as “very persistent and very bioaccumulative.” However, despite worrisome results from animal studies, there remains a scarcity of data concerning its impact on human health.

“Comprehensive research in this area is lacking, leaving us uncertain about the extent of harm these chemicals may cause through prolonged inhalation,” Jung noted. “While there have been studies on ‘wash-off’ products like shampoos, research on ‘leave-on’ products such as hair gels, oils, creams, waxes, and sprays is notably scarce.”

Additionally, Jung’s investigation revealed that subjecting these chemicals to high temperatures, such as when using curling irons or hair straighteners, amplifies their release into the air. Researchers observed that chemical emissions from hair care products increased by 50% to 310% when exposed to temperatures of 210 degrees Celsius.

To compound the issue, these airborne chemicals do not remain confined to a single room or household.

Jung elucidated, “Residential ventilation is a significant conduit for the transport of siloxanes from indoors to the outdoor environment. This poses a substantial concern in urban areas, where numerous homes release potentially harmful chemicals into the atmosphere concurrently, especially during morning preparations for work and school. Subsequently, these chemicals re-enter buildings through ventilation systems, impacting even those who do not use such products in their hair care routines.”

Surveys indicate that 16% to 70% of individuals use leave-on hair care or styling products. Considering an average frequency of two to five uses per week, the cumulative indoor-to-outdoor emission of D5 siloxane could range from 0.4 to 6 metric tons annually in the United States, based on data on hair care product usage patterns.

So, how can individuals safeguard themselves from inhaling these perilous chemicals?

“The optimal solution is to refrain from using these products altogether,” Jung advised. “I personally used similar products for hair straightening, but after scrutinizing the data, it became evident that the best way to protect my health was to discontinue their use.”

For those who cannot completely forgo these products, the next best course of action is to employ exhaust fans to minimize chemical inhalation, as suggested by Jinglin Jiang, a Purdue civil engineering PhD student and researcher.

“Ventilation can be an effective means of reducing siloxane exposure during indoor hair care routines,” Jiang explained. “Our model demonstrates that activating the bathroom exhaust fan can reduce inhalation exposure to D5 by over 90%.”

However, this approach also comes with environmental consequences. Jung’s research reveals that cumulative indoor-to-outdoor D5 emissions reach 710 milligrams within three hours without the exhaust fan, whereas running the exhaust fan continuously results in 900 milligrams emitted within just one hour.

“There’s a valid reason why certain regions have restricted the use of these chemicals in rinse-off hair care products,” Jung asserted. “The impact on both human health and the environment necessitates further investigation and regulatory measures.”

The research conducted by Jung’s team took place in a residential architectural engineering laboratory known as the Purdue zero Energy Design Guidance for Engineers (zEDGE) Tiny House, designed by Jung herself.

zEDGE, a mechanically ventilated, single-zone residential structure with a conditioned interior, was equipped with a state-of-the-art proton-transfer-reaction time-of-flight mass spectrometer (PTR-TOF-MS) from Jung’s laboratory. This instrument was used to monitor D5 siloxanes and other volatile chemicals in indoor air in real-time, second by second.

The experiments involving hair care routine emissions encompassed three types: realistic hair care experiments replicating actual routines, hot plate emission experiments examining the impact of temperature on emissions, and surface area emission experiments investigating the influence of hair surface area on emissions during grooming.

For the realistic hair care routine experiments, participants brought their own hair care products and styling tools to replicate their usual routines in zEDGE. These experiments involved a sequence of four periods to simulate a real-life routine.

After styling their hair, participants had two minutes to collect their tools and leave the laboratory. Subsequently, a 60-minute concentration decay period followed, during which zEDGE remained unoccupied while the PTR-TOF-MS monitored the decline in indoor volatile organic compound concentrations. The study focused on indoor volatile organic compound concentrations and emissions during and after active hair care routine periods.

Reference: “Siloxane Emissions and Exposures during the Use of Hair Care Products in Buildings” by Jinglin Jiang, Xiaosu Ding, Satya S. Patra, Jordan N. Cross, Chunxu Huang, Vinay Kumar, Paige Price, Emily K. Reidy, Antonios Tasoglou, Heinz Huber, Philip S. Stevens, Brandon E. Boor and Nusrat Jung, 16 November 2023, Environmental Science & Technology.
DOI: 10.1021/acs.est.3c05156

This research received financial support from Purdue University, the Alfred P. Sloan Foundation, and the National Science Foundation. Jung’s team intends to explore other chemicals identified in these experiments that were not covered in this study.

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More about Hair Care Chemicals

• Purdue University Study
• Environmental Science & Technology Journal
• European Chemicals Agency
• Hair Care Product Usage Patterns
• Purdue Zero Energy Design Guidance for Engineers (zEDGE)
• National Science Foundation
• Alfred P. Sloan Foundation