The influence of air pollution on skin microbiome: a link to skin barrier dysfunction

An equilibrium of skin microbiome is crucial for maintaining skin barrier function. However, external factors such as air pollution have the potential to disrupt this equilibrium. Hence, further investigation into the influence of air pollution on the skin microbiome emerges as a critical imperative. Healthy women matched for age from two different ambient air cities in Thailand: Bangkok, characterized by highly polluted air (HPA) (n = 33), and Songkhla, characterized by less polluted air (LPA) (n = 33) were recruited. Skin barrier physiological parameters were measured on the forehead skin. Microbiome samples were collected via the scraping and swabbing technique from the forehead skin and analyzed for microbiome profiles using amplicon sequencing. We found that the abundant microbiome at the phylum level was comparable between HPA- and LPA-exposed skin. However, microbiome diversity was decreased at genus level of fungus and species level of bacteria on HPA-exposed skin. Interestingly, some relatively higher enriched microbiome correlated with skin barrier physiological parameters. Specifically, a higher enrichment of Streptococcus parasanguinis on LPA-exposed skin correlated with both lower skin pH and higher stratum corneum (SC) hydration. Conversely, a higher enrichment of Malassezia spp. and Aureobasidum spp. on HPA-exposed skin was correlated with increased transepidermal water loss and decreased SC hydration, respectively. In conclusion, air pollution potentially affects the skin microbiome by reducing its diversity, disrupting its beneficial correlations with barrier physiology, and promoting the overgrowth of pathogenic microbiome, resulting in decreased hydration and increased pH levels. These factors could ultimately lead to skin barrier dysfunction.