The impact of airborne pollution on skin

Abstract

Indoor and outdoor airborne pollutants modify our environment and represent a growing threat to human health worldwide. Airborne pollution effects on respiratory and cardiac health and diseases have been well established, but its impact on skin remains poorly described. Nonetheless, the skin is one of the main targets of pollutants, which reach the superficial and deeper skin layers by transcutaneous and systemic routes. In this review, we report the outcomes of basic and clinical research studies monitoring pollutant levels in human tissues including the skin and hair. We present a current understanding of the biochemical and biophysical effects of pollutants on skin metabolism, inflammatory processes and oxidative stress, with a focus on polyaromatic hydrocarbons and ground-level ozone that are widespread outdoor pollutants whose effects are mostly studied. We reviewed the literature to report the clinical effects of pollutants on skin health and skin ageing and their impact on some chronic inflammatory skin diseases. We also discuss the potential interactions of airborne pollutants with either ultraviolet radiation or human skin microbiota and their specific impact on skin health.

Figure 1

Direct and indirect pollution uptake – Biochemical and clinical effects of pollutants and potential interactions with UV light. Direct dermal uptake with the accumulation of airborne pollutants (PAHs, PM, O3; black dots) on the stratum corneum and subsequent penetration. Indirect dermal uptake in the dermis and basal epidermal layer with the systemic blood distribution of inhaled or ingested pollutants that may have been metabolized (black dots). Left panel: Airborne pollutants (black dots) penetrate the skin directly or indirectly (black arrows) and induce biochemical effects such as an increase in the production of ROS via the aryl hydrocarbon receptor, an elevation of lipid peroxidation, protein oxidation and cell death (apoptosis), and a reduction in cell proliferation and antioxidant and ATP levels. Clinically, the effects of pollutants correspond to the exacerbation of skin ageing processes, the symptoms of inflammatory diseases (e.g. atopic dermatitis) and the deregulation of skin moisture. Right panel: UV radiation penetrates the skin where it might induce the production of ROS. In addition, some pollutants located at the surface or within the skin might induce the production of ROS (red and black filled circles). The combination of UV radiation and pollutants might exacerbate the biochemical and clinical effects of airborne pollutants. ATP, adenosine triphosphate; O3, ground‐level ozone; PAHs, polycyclic aromatic hydrocarbons; PM, particulate matter; ROS, reactive oxygen species; UV, ultraviolet.