Pollution, a Relevant Exposome Factor in Skin Aging and the Role of Multi-benefit Photoprotection.

Skin aging is a complex, continuous, multifactorial process resulting from cumulative morphological and functional changes in the skin over time. This happens because of two processes: intrinsic and extrinsic skin aging. Intrinsic skin aging occurs naturally over time and reflects each person's genetic makeup, or heredity. Extrinsic skin aging, on the other hand, is due to exposomal factors, such as solar radiation, air pollution, tobacco or nutrition, being the first two the most important of all. Exposure to air pollutants, primarily gases such as ground-level ozone and particulate matter, can accelerate the process via four key mechanisms: reactive oxygen species generation, inflammation, skin microbiome disruption, and aryl hydrocarbon receptor activation. Regarding solar radiation, all wavelengths reaching the Earth's surface have an impact on the skin, having a synergistic effect with air pollution ("photo-pollution"). Here, we discuss this phenomenon and mitigation strategies, including sunscreens, cosmetics with film-forming plus antioxidant ingredients, and oral supplementation.