Environmental Air Pollutants Affecting Skin Functions with Systemic Implications

The increase in air pollution worldwide represents an environmental risk factor that has global implications for the health of humans worldwide. The skin of billions of people is exposed to a mixture of harmful air pollutants, which can affect its physiology and are responsible for cutaneous damage. Some polycyclic aromatic hydrocarbons are photoreactive and could be activated by ultraviolet radiation (UVR). Therefore, such UVR exposure would enhance their deleterious effects on the skin. Air pollution also affects vitamin D synthesis by reducing UVB radiation, which is essential for the production of vitamin D-3, tachysterol, and lumisterol derivatives. Ambient air pollutants, photopollution, blue-light pollution, and cigarette smoke compromise cutaneous structural integrity, can interact with human skin microbiota, and trigger or exacerbate a range of skin diseases through various mechanisms. Generally, air pollution elicits an oxidative stress response on the skin that can activate the inflammatory responses. The aryl hydrocarbon receptor (AhR) can act as a sensor for small molecules such as air pollutants and plays a crucial role in responses to (photo)pollution. On the other hand, targeting AhR/Nrf2 is emerging as a novel treatment option for air pollutants that induce or exacerbate inflammatory skin diseases. Therefore, AhR with downstream regulatory pathways would represent a crucial signaling system regulating the skin phenotype in a Yin and Yang fashion defined by the chemical nature of the activating factor and the cellular and tissue context.

Automated summary

The increase in air pollution worldwide poses a global environmental risk to human health. The skin is exposed to harmful air pollutants, which can lead to cutaneous damage. UV radiation can activate photoreactive pollutants, enhancing their detrimental effects on the skin. Air pollution also reduces UVB radiation, inhibiting vitamin D synthesis and compromising cutaneous structural integrity. Moreover, air pollution can interact with skin microbiota and trigger or worsen skin diseases through oxidative stress and inflammatory responses. The aryl hydrocarbon receptor (AhR) plays a crucial role in responding to (photo)pollution and targeting AhR/Nrf2 could be a promising treatment for inflammatory skin diseases caused or exacerbated by air pollutants. Hence, AhR and its downstream regulatory pathways are important signaling systems that regulate the skin phenotype.