Adverse Effects of Airborne Heavy Metals on Human Skin Cells: Insights From Sebum Analysis of Indoor and Outdoor Workers.

Heavy metals in particulate matter (PM) contribute to oxidative stress, DNA damage, and inflammatory responses in skin cells. This study aimed to investigate the toxic effects of airborne heavy metals on human sebocytes, keratinocytes, and ex vivo skin. To this end, we collected sebum samples from indoor (n = 62) and outdoor (n = 40) workers in Shanghai and quantified the concentrations of 24 metals using inductively coupled plasma mass spectrometry (ICP-MS). Outdoor workers exhibited higher levels of cobalt (0.0004 vs. 0.39 mg/kg, 924.7-fold), arsenic (0.11 vs. 14.15 mg/kg, 134.7-fold), barium (0.70 vs. 20.24 mg/kg, 28.8-fold), and manganese (0.86 vs. 14.93 mg/kg, 17.3-fold) than indoor workers. Sebum-mimicking metal mixtures (SMMs), formulated to reflect the specific heavy metal profiles identified in the workers' sebum, were applied to human epidermal keratinocytes and sebocytes. Outdoor SMMs significantly reduced cell viability, increased lipid peroxidation, and induced DNA damage, as evidenced by the phosphorylation of histone H2AX (γH2AX) foci formation. Real-time quantitative reverse-transcription polymerase chain reaction (RT-qPCR) analysis revealed upregulated IL1A, IL1B, TNFA, IL6, and PTGS2 mRNA, primarily after treatment with outdoor SMMs. Further activation of the NF-κB and MAPK signaling pathways was also identified. This was corroborated in human scalp skin models, in which exposure to outdoor SMMs increased the expression of proinflammatory cytokines, including interleukin-1β (IL-1β) and IL-6, and decreased the expression of keratin 10. These findings highlight the detrimental effects of environmental heavy metals on skin homeostasis, providing a scientific basis for the development of antipollution skincare formulations.