ANTI-POLLUTION
Designing new anti-pollution cosmetics
Annette Mehling, Petra Schulte – BASF Care Creations
Pollution is the introduction of contaminants into the natural environment that endanger human health and/or the environment. It can take the form of chemical substances or energy, such as noise, heat or light. Pollutants, the components of pollution,
can be either foreign substances or energies, or naturally occurring contaminants. From cars and industrial emissions to dust storms, pollen and smoke inside the home, air pollution poses a major threat to our health and the climate. According to the WHO, 90% of us are exposed to it.1 Airborne particular matter (PM) with
diameters of <10 µm and in particular of <2.5 µm is associated with serious health effects, including cardiovascular disease and lung damage, but also with skin health issues. The skin, the interface between the environment and the body, is the first site of contact with pollutants, regardless of type and size.2-4
PM
and adhering substances can: ■ Exacerbate (inflammatory) acne ■ Be a carrier for environmental stressors associated with extrinsic premature skin ageing, such as polycyclic aromatic hydrocarbons (PAHs) ■ Up-regulate genes associated with ageing, pigmentation disorders and wrinkle formation, such the aryl hydrocarbon receptor (AHR) or matrix metalloproteinases (MMPs) Other major components of pollution
affecting skin health include: UV light, blue light, ash, pollen, dust, ozone, sulfur compounds,
heavy metals, smoke, smog, NOx, COx, SO2 and reactive oxygen species (ROS). Exposure to these can alter the composition of the skin microbiome and skin barrier. It can also lead to oxidative stress, causing inflammation and the formation of ROS, or oxidise proteins, lipids, DNA, etc., causing further skin damage. Because of concerns like these, the number
of new skin care launches with anti-pollution claims has been growing rapidly in recent years and in all regions of the world, from 1,276 in 2016 to 2,413 in 2020 (Figure 1).
Tests for PM BASF has been developing cosmetic concepts that help reduce PM’s negative effects. We began by systematically evaluating the efficacy of each functional ingredient. Consumers rarely put an active or a UV filter directly on their skin; these are almost always in the form of a formulation, comprising emollient, emulsifiers and polymers, as well as the active. We also
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developed novel test methods to evaluate the efficacy of the ingredients and formulations for the specific application type, and designed formulations that take the efficacy of each ingredient into consideration. First, we identified different mechanisms
that could play a role in targeting the effects of PM, based on best-in-class ingredients and product efficacy. These comprise: ■ Anti-adhesion: Reducing the adhesion of pollutant particles from pre-treated skin ■ Removability: Enhancing the rinse-off of adhered pollutant particles from pre-treated skin ■ Anti-penetration: Decreasing the penetration of harmful substances into the skin ■ Cleansing: The active removal of pollutant particles from the skin Because PM usually reaches our skin via the
air, we designed a method for testing anti- adhesion and removability that applied PM to the skin via an airburst inside a fume hood. This avoids inadvertent inhalation by volunteers and the associated inhalation (toxicological) issues. The formulation was applied and dried,
then the test pollutant – activated charcoal with mean particle sizes of 80 and 2.5 µm – was applied and rinsed off with clear water. Pictures were taken at each stage. Using image analysis, we could see how much remained on the skin and evaluate the anti-adhesion and removability performance of our ingredients. Figure 2 shows the performance of various
polymers that were incorporated as 1% active matter. Most reduced the adhesion of the PM
■Europe ■Asia Pacific ■North America ■Latin America ■Middle East & Africa
1,276 49%
2% 1%
32% 16%
2016 1,566
to the skin relative to the untreated skin (the zero line) but some of them actually increased it and are thus unsuitable for this application. Emollients, by contrast, generally increase model pollutant adhesion. The pictures show two examples of how
different polymers performed: Hispagel® 200 (INCI: Glycerin (and) Glyceryl Polyacrylate), which scored badly for adhesion but quite well for removability; and Rheocare® XGN (INCI: Xanthan Gum), which was one of the ‘star ingredients’, doing well on both counts. The pictures in Figure 2 also show that rinse-off has very little effect on untreated skin. For the anti-penetration test, commercially
available plates were used. These have a membrane that mimics the skin barrier properties of the stratum corneum. We applied the test substance to this membrane, waited for it to dry, then put a model pollutant, in this case a fluorescent dye, on top. Anything that goes through to the lower chamber can be regarded as penetrating the skin. Based on this test method, we evaluated the
performance of different ingredients, such as polymers (Figure 3) and these proved to have highly varied effects. All of the emollients and some of the polymers decreased penetration. The star ingredients, again including xanthan gum, were used for the development of the formulation. Our test model for cleansing used a collagen
membrane as a surrogate for the skin. We applied a sebum pollutant model onto an area of this biomatrix and took a picture of the
2,016 2,389 51% 52% 47% 26%
3% 3%
35% 13%
2017 29%
3% 2%
15% 2018 17%
3% 2%
2019
Figure 1: Number of new skin care launches with anti-pollution claims, 2016-2020 Note: Source – Mintel
November 2021 PERSONAL CARE
5% 3%
2020 16% 28% 2,413 49%
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