Air pollutants break your hair

Organic pollutants damage the fine structure and promote UV damage in the hair

How shiny and healthy our hair is also depends on the cleanliness of the air in our living environment. © Photoattractiv / iStock
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Damage caused by thick air: If the hair becomes stained and spotty, it is not always faulty care. Even a strong air pollution can measurably damage the hair structure, as a study reveals. Accordingly, organic air pollutants lead to the destruction of pigments and the finest fractures. In addition, they increase the harmful effects of UV radiation in the sun, as the researchers report.

A healthy, shiny head hair is considered an important beauty feature. But our hair does not have it easy. Because after the individual hairs have been formed by the follicle, they are only dead material. They consist mainly of keratin fibers and dead cells in which coloring pigments are incorporated. As a result of environmental damage such as exposure to the sun, chemicals or mechanical stimuli, the hair can no longer repair itself.

A single hair under the microscope. One recognizes the scale structure of the outer shell consisting of dead cells. © Jan Homann / Public domain

How does the air pollution affect the hair?

But there is another factor that can damage our hair: air pollution. This is revealed in a study conducted by Gregoire Naudin of the L'Oreal Research Center in collaboration with colleagues from the Luxembourg Institute of Health. The researchers collected hair samples from approximately 100 women aged 25 to 45 in the Chinese cities of Baoding and Dalian. Both cities are in a similar position and have a comparable climate.

The key difference, however, is that Baoding has significantly higher levels of air pollution than Dalian, as measured over several months. Accordingly, the values ​​for particulate matter, ozone, nitrogen oxides and sulfur dioxide, but also for organic pollutants such as polycyclic aromatic hydrocarbons (PAH), are permanently higher in Baoding than in Dalian.

"Empty zones" in the hair

Would these differences also be noticeable in the hair samples? To find out, the researchers examined a section about 20 centimeters from the root of all hair samples this corresponds to a hair age of about 1.5 years. They analyzed the microstructure of the hair by electron microscopy and used gas chromatography to determine the content of PAHs in the hair samples. display

The result: In fact, there were clearly visible differences between the hair samples: the hair that was exposed to the more polluted air in Baoding had significantly more white, empty zones. "Such damage is also observed in chemically treated and over time aged hair, " report Naudin and his colleagues. These vacancies therefore arise when pigments, cells and other biological components are lost through breakage and other microprotects.

More PAHs - more hair loss

Another analysis revealed that the hairs that have the highest levels of PAHs also showed the most microscopic damage. This correlation was still evident when the researchers mixed the hair samples from both cities and grouped them only according to their pollutant contamination. The most heavily contaminated hair had lost an average of two cuticle layers per year and suffered 2.7% more damage to the keratinous fiber layer of the hair. In the case of little-contaminated hair, on the other hand, it was only a cuticle layer and 0.67 percent damage per year, as reported by Naudin and his team.

"To our knowledge, this is the first time that an association of PAH concentrations in the hair with pronounced structural changes has been found, " say the researchers. "The naturally occurring damage appears faster on hair with higher PAH concentrations." They suggest that the organic pollutants release aggressive oxygen compounds in the hair that damage cells and keratin fibers.

Sensitive to UV radiation

But one more thing turned out: when the hair was exposed to UV radiation, which naturally occurs on 60 sunny days, it reacts differently depending on the level of pollution. The hairs with an elevated PAH concentration were more sensitive to UV radiation and more than twice as likely to cause new damage, the researchers said. They conclude that the presence of pollutants and the aggressive oxygen compounds they produce enhances the harmful effects of UV radiation.

According to the researchers, this demonstrates that air pollutants such as PAHs not only harm our health but also our hair. They cause damage to the microstructure of the hair and exacerbate the harmful effects of UV radiation. "Our results also indicate that these negative effects of PAHs could also occur in other human tissues such as the skin, " say Naudin and his colleagues. (Proceedings of the National Academy of Sciences, 2019; doi: 10.1073 / pnas.1904082116)

Source: Proceedings of the National Academy of Sciences

- Nadja Podbregar