How Pollution Disturbs the Skin

“Should we give credit to cosmetics claimed to be ‘anti-pollution’? Maybe we should, if they contain the right ingredients for it. Indeed, what is now for certain is that poor environmental conditions have a real negative impact on the skin’s condition. In a conference presented at the Beyond Beauty show, Marc-André Lefebvre, of L’Oréal, presented the research his group conducted, and which contributed to providing evidence of this.

As an expert in analytical chemistry, he managed L’Oréal‘s product assessment department for a long time. Today, Marc-André Lefebvre presents himself as the spokesman for both the group and its teams of researchers who have been working on the following question for several years: what are the consequences of poor environmental conditions on the skin?
The objective was to determine whether they were real, important, if it were possible to provide evidence of them, measure them, and document them in order to, of course, prevent them or correct them with cosmetic products.
It took many years and four studies, from Paris to Shanghai, and even Mexico, to come up with the results Marc-André Lefebvre presented.
‘This is not an easy issue to tackle’, the researcher underlined, ‘especially if one wants to take into account the complexity of all exposures, and even their quantification. And it requires considerable means’.
The L’Oréal group already had significant expertise in the field of sun protection and in-depth knowledge of UV consequences on the skin.
Many assessment techniques have been developed, in particular biophysical and biochemical methods, to which analytical tools were added for determining what occurs at the interface between the outside world and the skin, and particularly in the stratum corneum, the most superficial and accessible layer of the skin.

Preliminary study

It all started in 1998 with the simplest of protocols.
‘We picked up only one subject, a volunteer, who accepted to take part in this experience and be exposed to Parisian pollution for only one day’, Marc-André Lefebvre recalled. ‘He walked in the most crowded streets, took the metro… He did a real tour of Paris. Half his face and one of his arms were protected to be able to compare a certain number of cutaneous parameters between the area of the skin that was exposed and the area that was not. With half his face hidden, he got quite a lot of attention, especially in the metro!’
Thanks to this experience, researchers were able to collect and assess all the pollutants contained in the environment which had deposited on the skin exposed. In addition, they could measure a few biological, biophysical, and analytical parameters that they expected would change. That is how they found numerous differences between the areas exposed and the areas protected: among others, hydration, pH, secretion of sebum, vitamin E, squalene…
The speaker recognized that ‘objectively, with only one subject, it is quite hard to determine whether the differences found are statistically significant, but at the time, it represented good indications for our studies to come.’

Pilot study

Conducted in 2000, it followed a much more traditional protocol, with two separate populations (eight subjects, all in all), in two different exposure places, for two days: Paris again, and Neauphle-le-Château, a town in a region that is not much exposed to poor environmental conditions. Researchers measured the same parameters as those that had been identified during the preliminary study, with the same type of measurements, in vivo and in vitro.
And what did they find? ‘All initial parameters were not significant’, Marc-André Lefebvre indicated, ‘but several were confirmed’. In particular, the increase of the secretion of sebum, the identification of oxidation processes involving a decrease in vitamin E and squalene, an increase in lactic acid, and a decline of the barrier function. ‘This study showed that pollution has a real impact on the skin’, the researcher commented, ‘since some parameters are significantly modified and can be assessed’.

Mexico study

Still in 2000, the L’Oréal group decided to shift to a more large-scale approach, in partnership with two public organizations (the Centre régional de lutte contre le cancer of Montpellier, a regional cancer institute in the south of France, and the National Public Health Institute of Mexico). They used a larger cohort of volunteers (189 subjects, all in all) and an additional dimension: the study was conducted by dermatologists that were to determine whether any dermatological signs could be identified in addition to biochemical, biophysical, and analytical measurements.
There were 96 subjects in Mexico City, considered as one of the cities with the poorest environmental conditions in the world, and 93 in Cuernevaca, known in Mexico as ‘The City of the Eternal Spring’, and where conditions are much more favourable.
‘We proceeded to the assessment of the same parameters, in addition to the clinical evaluation carried out by the dermatologists’, Marc-André Lefebvre explained.
The results obtained were coherent with what had been demonstrated during the preliminary and pilot studies: increased sebum excretion, a very impacted oxidation process, modifications in the barrier function, decreased hydration… And the clinical evaluation confirmed these results.

Shanghai study

‘The Mexico study was a turning point for us, as it led us to conduct an additional study in 2008 in China, where the environmental conditions are critical in a few big cities’, the researcher explained.
This new study was conducted with 160 volunteers in the region of Shanghai, on two different sites, one of them presenting poor environmental conditions, the other benefitting from ‘acceptable’ conditions.
‘The originality of the study conducted in China was that we had also prepared a questionnaire to collect the participants’ impressions and see whether there was a correlation between what was observed in terms of biophysical and analytical parameters and the individual self-assessment of volunteers’, Marc-André Lefebvre specified. ‘It made it possible to reconfirm what had already been found on a lower number of parameters, but we were able to confirm the aspects related to the oxidation process and desquamation’.
The results of this experimentation were published in the International Journal of Cosmetic Science.


‘If we sum things up’, Marc-André Lefebvre declared, ‘our approach did take us a long time, for different reasons: the issue was a tricky one. We started with an original approach involving a subject that was his own witness, and we observed what changed. The parameters that were evidenced were confirmed in a pilot study, which was more “respectable” in terms of clinical ethics, and then these results were confirmed by a study conducted in Mexico, which included a dermatological part, and a study in Shanghai, with an evaluation carried out by consumers’.
Then he reminded the main effects of pollution on the skin:

• The production of sebum increases, and its composition is modified
• The oxidation process is considerably impacted: decrease in vitamin E and squalene, increase in oxidized proteins, which were measured in a few studies
• The barrier function is weakened
• Some biochemical parameters are modified…

All this was observed after short exposures to poor environmental conditions: one or two days were enough to notice modifications on the skin!
However, researchers do not intend to stop here: ‘we still need to find out why these parameters are modified’, Marc-André Lefebvre indicated. ‘L’Oréal keeps trying to identify the biochemical changes that occur on the skin, and it is a whole world that needs to be understood’. It could also be interesting to know which pollutant or environmental condition is responsible for which modification. To the speaker, ‘it is an extremely complex issue… but we will get to it!’

Cosmetic answers

The cosmetic approach arises from the results of these studies. It aims to offer solutions adapted to these exposures.
Marc-André Lefebvre mentioned four weapons that can be developed to protect the skin:

• Specific products adapted to the environmental conditions observed
• Products that remove dust, microparticles, etc., and that cleanse the skin so that environmental pollution agents have less effects on it
• The use of emollients to restore and/or enhance the barrier function, so as to prevent the penetration of a certain number of polluting agents
• The use of antioxidants to thwart oxidation processes…

And one should not forget about photoprotection, the speaker added, as we know UV exposure (UVAs and UVBs) potentiates the effects of pollutants.
‘There is still a lot to do’, concluded Marc-André Lefebvre. ‘All these gradually implemented data are still only avenues to explore. The explanation to all the phenomena identified remains to be scientifically proven, but we do have evidence that poor environmental conditions have an impact on the skin, and that this impact may be documented, and eventually corrected’.”


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