Development of an in Vitro Inhalation Method for Characterization of Aerosols Released During the Use of Hair Products

Introduction: Aerosols generated from heated hair products may pose respiratory risks, particularly for hairdressers due to occupational exposure. While some products show a higher potential for these effects, a clear link toward product and application methods remains unestablished. This study aimed to evaluate a cell-based in vitro inhalation approach to better understand the toxicological impacts, screen existing products, and facilitate the “safe-by-design” approach. Materials and Methods: Four test materials (TM1–TM4), including different products, application techniques, and subtle real-life effects observed after prolonged use, were evaluated, including two methods for TM2 (TM2 and TM2A). Aerosols were generated by product application to real hair strands and sampled by exposure of human lung cells (A549) under optimized conditions (P.R.I.T. ® ExpoCube ® ). Dose–response testing assessed cell viability, mitochondrial function, cellular stress, and interleukin-8 release. Results: Results indicated significant differences in aerosol release based on the test material and application method. Cell viability and mitochondrial function generally remained unaffected; however, there were notable differences in cellular stress and IL-8 release. A score was developed to facilitate a general assessment of the test materials, evaluating both aerosol release and biological effects. It showed promising correspondence between in vitro results and real-life observations. Conclusion: This in vitro –based alternative to animal testing has the potential to provide a strategy to investigate the respiratory effects of cosmetic product aerosols. It might offer a framework for product screening and, as experience with additional test compounds accumulates, could help facilitate the development and acceptance of alternative methods in safe-by-design and safety assessment strategies.