Toxicological Assessments of Released Engineered Nanoparticles from Aerosolized Products on Human Small Airway and Bronchial Epithelial Cells

Nanotechnology has led to the development of novel applications and materials incorporated into consumer products known as nano-enabled products (NEPs). Consequently, the wide-spread use of NEPs has led to a concern of human exposure to constituent engineered nanomaterials (ENMs) utilized in the consumer products. This growing public health issue is largely due to limited safety regulations imposed on manufacturers and a lack of hazard characterization of NEP exposures to understand the human health implications. This in vitro study focused on NEPs such as aerosolized cosmetics, which are becoming more mainstream within the general population. A large majority of constituent ENMs such as metal nanoparticles (NPs) that are heavily used in the cosmetic industry have been associated with asthma, inflammation, and other pulmonary conditions upon exposure. Within this study, we utilized a novel aerosol exposure system to monitor and sample released nanoparticle (rNP) aerosols from two separate cosmetic lines to determine potential differences in manufacture or production. The exposure system consisted of a stainless-steel glove box containing a mannequin head with fitted outlet sample portals that allowed monitoring of aerosols using scanning mobility particle sizer (SMPS). To generate cosmetic aerosols, an automated nebulizer controlled by proprietary software that controlled spray durations, length of exposures, and aerosol concentrations was fitted in the glove box. The enclosed glove box system was pressurized using a vacuum while HEPA filtered air was used to regulate air flow (11 L/min) and aerosol release from the nebulizer. The generated aerosols or rNPs were sampled or collected on to mixed cellulose ester (MCE) filters for subsequent aqueous extraction and off-line physico-chemical characterization of collected rNPs to determine particle morphology and elemental composition using scanning electron microscopy coupled with energy dispersive x-ray spectroscopy (SEM-EDS). Colloidal characterization was performed on extracted rNPs and pristine nanoparticles (pNPs) iron-oxide (Fe2O3) and titanium dioxide (TiO2), which are found in great quantities in each of the raw or whole cosmetics determined by inductively coupled plasma mass spectrometry (ICP-MS). The toxicological profiles of acute 24hour exposure to extracted rNPs and pNPs were then compared using human bronchial (16HBE) and primary small airway epithelial cells (SAEC) to model airway responses to NEP exposures. The results indicate that SAEC were most susceptible to exposure to rNPs than 16HBE. It was also determined that rNPs, specifically the darker shades of cosmetics induced higher levels of reactive oxygen species, oxidative stress, and cytotoxicity. Immunocytochemistry confirmed by western blot analysis of 3-week sub-chronic exposures to rNPs indicated epithelial mesenchymal transition (EMT), suggesting fibrotic changes in exposed SAEC. While further studies are needed to provide a more comprehensive picture of the effects of rNPs, this study has established findings that can be used towards future research regarding inhalation exposure to NEPs. Moreover, the findings indicate that susceptible populations such as darker skinned individuals or individuals with pre-existing conditions may be at higher risk to the adverse effects of NEP cosmetic exposures.