Increasing global air pollution levels caused by urbanization, industry and transport are recognized as a major public health concern. In 2021, the World Health Organization (WHO) updated its published air quality guidelines offering global direction and limits for key air pollutants that pose health risks including particulate matter (PM2.5 and PM10), ozone, nitrogen dioxide (NO2), sulfur dioxide (SO2) and carbon monoxide.1 The WHO report included an assessment of the health effects of air pollution and stated that in 2019, the majority of the world population (99%) was living in places where the WHO air quality guidelines were not met.
Polluted urban and indoor environments provide a range of airborne insults that can damage the skin and consequently impact the health of the whole body. Air pollutants generate reactive species that can cause oxidation and related mechanisms of disruption in skin cells, proteins and lipid layers.2-4 As is well-known, at physiological levels, reactive oxygen species (ROS) are generated as by-products of normal, healthy cell functioning. These are controlled and neutralized by the body’s antioxidant defense system. However, harmful effects can result when an overproduction of ROS overwhelms the body’s defenses.
This leads to an imbalance between the production and destruction of ROS within the skin cells and causes oxidative stress. Clinical manifestations of the effects of pollution in skin include aging (e.g., wrinkle formation and pigmented spots), imbalance of the skin microbiota, inflammatory skin disorders (e.g., acne, eczema and atopic dermatitis) and skin cancer.2, 4
Consumers are increasingly aware of the effects of air pollution on the skin and seek multifunctional protective products. The inclusion of anti-pollution ingredients in color cosmetics could provide convenient protection in consumers’ daily routines. However, this poses the challenge of combining the physical performance of a powder with functional performance to neutralize pollution.
Natural wool fibers are well-known to bind and neutralize NO2, SO2 and formaldehyde pollutant gases in urban environments due to their high natural cystine content.5-7 Ethically and sustainably sourced wool powder and pigments could therefore combine the particle size and insolubility requirements of color cosmetics with the performance of pollution protection.
The present work explores the potential anti-pollution efficacy of a wool powder and wool powder-based pigment in vitro and ex vivo; specifically examined were SO2-absorbing, antioxidant and cellular stress-reducing effects. Results suggest the material provides a high surface area and a rich array of chemical groups to which pollutant species can bind, neutralizing them before they can impact the skin. Future work aims to test this efficacy in cosmetic formulations.
Materials and Methods
Ingredients and characterization: Wool powdera was prepared using wool fibers from New Zealand sheep and proprietary processes. Red wool pigmentb was then prepared by combining FD&C Red 40 dye with the wool powder. For comparison purposes, red iron oxide powder also was purchasedc and activated carbon granules were extracted from commercial cartridgesd used for NO2(g) filtration.
Scanning electron microscopy (SEM) images were obtained for the test materialse and particle size and distribution were determined by laser diffractionf with ethanol as the dispersion medium. Nitrogen absorption/desorption isotherms were measured for Brunauer-Emmett-Teller (BET) surface area analysis. Poured and tapped densities were determined by standard methods.
- World Health Organization (2021). WHO global air quality guidelines: particulate matter (PM2.5 and PM10), ozone, nitrogen dioxide, sulfur dioxide and carbon monoxide. Available at https://apps.who.int/iris/handle/10665/345329.
- Puri, P., Nandar, S.K., Kathuria, S. and Ramesh, V. (2017). Effects of air pollution on the skin: A review. Indian J Dermatol Venereol Leprol 83 415-423.
- Rembiesa, J., Ruzgas, T., Engblom, J. and Holefors, A. (2018). The impact of pollution on skin and proper efficacy testing for anti-pollution claims. Cosmetics 5 4-12.
- Denisow-Pietrzyk, M. (2021). Human skin reflects air pollution–A review of the mechanisms and clinical manifestations of environment-derived skin pathologies. Pol J Environ Stud 30(4) 3433-3444.
- Crawshaw, G.H. (1978). The role of wool carpets in controlling indoor air pollution. Textile I Ind 12 12-15.
- Causer, S.M., McMillan, R.C. and Bryson, W.G. (1995). The role of wool carpets and furnishings in reducing indoor air pollution. Proc 9th Int Wool Text Res Conf. Biella (vol I) 155-161.
- Spicer, C.W., Coutant, R.W., Ward, G.F., Joseph, D.W., Gaynor, A.J. and Billick I.H. (1989). Rates and mechanisms of NO2 removal from indoor air by residential materials. Environ Int 15 643-654.
a Wool Source Powder (INCI: Keratin)
b Wool Source Pigment Red PC (INCI: Keratin (and) FD&C Red 40)
c Pure Nature
d 3M Organic Vapor
e JEOL JSM 7000F field emission system, accelerating voltage of 10-15 keV
f Mastersizer 2000, Malvern Instruments