Physiochemical properties of hair are impacted by many stressors ranging from physical, chemical, mechanical to environmental. A combination of several environmental factors such as sun exposure and air pollution can impact overall hair and scalp health. Damage induced by these aggressors impacts hair properties such as protein content, melanin oxidation, surface quality and structural components . Hair and scalp care go hand in hand and prolonged exposure to pollution can cause scalp sensitivity. In this article, we will discuss the impact of environmental factors on hair and some of the treatment strategies that can help protect hair against these harmful effects.
Hair is composed of heavily melanized keratin fibers. Hair keratins are classified as hard keratins, consisting of 65-96% proteins, 1-9% lipids, 3% melanin and other minor compounds. These proteins are the building blocks that contribute to the strength, flexibility, and overall health of hair. Hair is broadly structured in three layers: the cuticle, cortex, and the medulla. The cuticle forms the outermost coat of the hair shaft, acts as a protective wall shielding the inner layers and contributes to the feel and appearance of hair. The cuticle is subjected to many day-to-day insults such as washing, brushing, the use of thermal tools, UV radiation and pollution. Thus, the hair structure is gradually damaged. Next, we will review the impact of UV exposure and air pollution on hair properties.
Impact of UV radiation
Both UVA and UVB components of sunlight radiation are responsible for inducing damage to hair. It has been reported that morphological damage to the hair is caused by UVB and chemical changes in hair are caused by UVA .
UVB radiation (280-315 nm) affects hair approximately 5 µm beneath the surface  and localizes primarily in the cuticle area. It attacks the melanin pigment and protein fractions of hair . UVB range is more harmful than UVA for hair damage: once the main chromophore of hair proteins absorbs UVB, UVA acts as a secondary cause of damage . Effects of UVB radiation can be severe, resulting in the breakdown of di-sulfide bonds, which are fundamental to hair structural integrity. Such disruptions impact hair’s mechanical properties, resulting in the loss of tensile strength, increase in porosity and irregularities on the hair surface .
UVA radiation (315-400 nm) is less energetic but due to its longer wavelength, is capable of penetrating cuticle layers and cortex (causing partial loss of lipid, protein, and melanin) . However, UVA is primarily responsible for color changes in hair. In pigmented hair, melanin granules provide photoprotection to hair proteins and lipid components from oxidation. Therefore, blonde, and grey hair, which are low in melanin, are susceptible to more damage . Red and dark-brown hairs photo yellow when exposed to near ultraviolet plus visible radiation .
Overall, prolonged exposure to UV radiation can cause a decrease in 18-methyleicosanoic acid (18-MEA), a fatty acid found on the surface of hair cuticles and photochemical degradation of cystine, tryptophan and tyrosine. These changes contribute to signs of damage such as increased surface friction, poor manageability, brittle hair, and loss of shine, color, and tensile strength.
Impact of Pollution
Air pollutants consist of complex and varying mixtures of different size and composition particles suspended in the air. These can be polycyclic aromatic hydrocarbons (PAHs), volatile organic compounds (VOCs), nitrogen oxides (NOx), particulate matter (PM), ozone or cigarette smoke .
Particulate matter (PM) is classified into PM2.5 and PM10. Some PM2.5 particles form because of complex reactions between sulfur & nitrogen oxides and other compounds, which are pollutants emitted from power plants, industries, and automobiles . PM10 particulates like dust and pollen are much larger in size.
PM binds to the hair surface and infiltrates the hair follicle, something which could affect hair growth and texture. Severe air pollution can alter the hair surface making it rough and dull. The presence of sebum on the hair surface favors the deposit of larger PM. When it comes to your scalp, long term effects of pollution can contribute to scalp irritation, itching, excessive sebum secretion, dandruff, pain in the hair roots and hair loss. The combination of these symptoms is defined as sensitive scalp syndrome . Excessive sebum production on scalp translates into oily / greasy roots, clogged pores, and blocked hair follicles. This can lead to an effective weakening of the hair at the root, making it to more prone to breakage .
PAHs are among the most widespread organic pollutants and in addition to being a human health risk factor they can also damage hair . PAHs cling to the hair surface and the oxidizing pollutants penetrate inside the hair fiber, causing chemical damage to hair cuticle and protein. Furthermore, they can cause oxidative stress to hair when exposed to UV radiation; It is also shown that damage to cuticle and cortex is higher when PAH contamination increases and indeed fibers with increased PAH contamination show increased damaged after UV treatment .
Product Solutions to Combat Environmental Stressors
Consumers are always looking for products that help protect hair and scalp from these external aggressors. According to Mintel (GNPD, 2021) there has been a 61% increase in hair care product launches in North America with anti-pollution claims in the past three years. As consumers are shifting to healthier lifestyles and making cleaner choices, ingredients, their sources, and functionality are determining their purchase behaviors.
Film formers, UV filters and certain antioxidants have been used in hair care products to help protect hair from UV damage and prevent color fade. However, there is a growing need for multifunctional ingredients whose benefits go beyond sun protection alone, extending to helping protect hair and scalp against pollution as well.
The use of gentle cleansing ingredients to wash hair without disrupting scalp homeostasis has been a huge focus area for consumers. Botanical options such as Moringa and Chia seeds along with food-inspired ingredients like turmeric and bioinspired molecules (amino acids) have been spotlighted as ones that help purify, detox, and soothe the scalp. Antioxidants and anti-inflammatory ingredients like apple cider vinegar and exfoliators such as pink salt are in demand and help to stimulate good blood circulation. They can also help to remove build-up and excess sebum on the scalp.
As the photo-pollution category continues to evolve, researchers are now conducting exposome studies that can reveal new hypotheses on how hair could be affected by daily life environment and routine using wearable devices . The use of new data collecting devices and beauty apps continue to rise, as they help engage consumers and guide the cosmetic industry in developing new products and concepts.
Pollution and sun exposure are a global concern and the emphasis is beyond just skin. These stressors can cause hair damage and induce scalp sensitivity. Novel ingredients and new products that focus on providing full protection continue to advance. Key for hair and scalp health are protective hair and scalp care solutions that can help create an eco-barrier on the hair surface to prevent the adhesion and penetration of pollutants and radiation, restore hair from the inside-out and provide scalp bio balance.
- Rodrigo De Vecchi, Júlia da Silveira Carvalho Ripper, Daniel Roy, Lionel Breton, Alexandre Germano Marciano, Plínio Marcos Bernardo de Souza & Marcelo de Paula Corrêa, “ Using wearable devices for assessing the impacts of hair exposome in Brazil” , Scientific Reports ,volume 9, 13357 (2019)
- Kazuhisa Maeda, Jun Yamazaki, Nana Okita, Masami Shimotori, Kyouhei Igarashi and Taiga Sano, “Mechanism of Cuticle Hole Development in Human Hair Due to UV-Radiation Exposure”, Cosmetics, 24, 5(2) (2018)
- Lee, W. S.,” Hair photoaging “Aging hair, Springer, 123-133 (2010)
- Estibalitz Fernández, Blanca Martínez-Teipel, Ricard Armengol, Clara Barba, Luisa Coderch, “Efficacy of antioxidants in human hair”, Journal of Photochemistry and Photobiology B: Biology 117,146-156 (2012)
- Timothy Gao, Jung-Mei Tien, Abhijit Bidaye, Scott Cardinali and Jena Kinney, “A Diester to Protect Hair from Color Fade and Sun Damage”, Cosmetics & Toiletries (2013)
- Ernesta Malinauskyte; Samuel Gourion-Arsiquaud, “Dirty Air, Hair and Skin: Pollution Studies”, TRI talks
- Trefor A. Evans, “Combing Through Sun and Pollutant Effects on Hair”, Cosmetics & Toiletries (2016)
- Eleni Drakaki, Clio Dessinioti and Christina V. Antoniou, “Air pollution and the skin”, Frontiers in Environmental Science (2014)
- Seinfeld, J. H., & Pankow, J. F “Organic atmospheric particulate material”, Annual review of physical chemistry, 54(1), 121-140 (2003)
- Rajput R, “Understanding Hair Loss due to Air Pollution and the Approach to Management”, Hair Therapy and Transplantation (2015)
- Ashland: “How air pollution can turn into air pollution, and solutions to prevent it” Cosmetics design-europe.com (2019)
- Sharleen St. Surin-Lord, “Sun, Metals & Pollution Are Damaging Your Hair”, Happi (2020)
- Gregoire Naudin, Philippe Bastien, Sakina Mezzache, Erwann Trehu, Nasrine Bourokba, Brice Marc Rene Appenzeller, Jeremie Soeur and Thomas Bornschlogl, “Human Pollution exposure correlates with accelerated ultrastructural degradation of hair fibers”, PNAS, 116(37), 18410-18415(2019)
Mythili Nori has worked in the Personal Care industry for over a decade. Her expertise is in Product Claim Substantiation and Data Science. In her current role at BASF, she is responsible for Physical Claim Substantiation & Sensory testing for Hair & Skin Care. Prior to joining BASF, she spent 5 years at TRI/Princeton as a Senior Research Associate, supporting claim substantiation and fundamental research activities for textile and hair surfaces. She earned a Bachelor of Technology in Chemical Engineering from India and received Master of Science in Chemical Engineering at North Carolina Agriculture & Technical State University focusing on purification of drinking water.