Evaluation of Chronic Inhalation Toxicity of E-Vapor Aerosols in an 18-Month Study in AJ Mice

      Wong, E.; Luettich, K.; Woon, K.; Yeo, Y.; Kratzer, G. F.; Kondylis, A.; Kumar, A.; Smith, C.; Peitsch, M. C.; Hoeng, J.; Lee, K.; Vanscheeuwijck, P.

      Conference date
      Mar 30, 2021
      Conference name
      Society of Toxicology (SOT) Annual Meeting and ToxExpo 2022

      Many flavor ingredients in e-liquid formulations are ‘generally recognized as safe’ for oral consumption, however there is limited information on their inhalation toxicity especially after repeated exposures. Based on structural grouping, we selected 38 flavor group representatives from a total of 245 flavor chemicals, which were combined as prototype e-liquid formulations and tested in an 18-month inhalation study in AJ mice. The objectives were to characterize and compare the potential impact of flavor containing e-vapor aerosols to the chronic inhalation toxicity of cigarette smoke. Mice were whole-body exposed to air, aerosol from carriers propylene glycol (PG) and vegetable glycerol (VG), PG/VG with nicotine (N, 2% [w/w]), PG/VG/N with flavors (F) at low, medium and high concentrations (4.6 to 18.6% [w/w]), PG/VG/F-High or to mainstream smoke (MS) from the 3R4F reference cigarette for 6 h/day, 5 days/week for up to 18 months. The target aerosol nicotine concentration was set to 15 μg/L. The main endpoints consisted of systemic toxicity (body weight, survival), pulmonary inflammation (bronchioalveolar lavage fluid [BALF] analyses), clinical chemistry, and whole blood analyses. No signs of severe toxicity were noted following exposure to e-vapor aerosols and MS. There were no exposure-related differences in survival rates amongst the female groups, but the survival rate was lower in the male PG/VG/F-High group. Body weights at month 18 were lower in the male PG/VG/F-High and male and female PG/VG/N/F-High groups, however, all the e-vapor aerosol groups showed consistently higher body weights compared to the MS group. In contrast to MS exposure, exposure to the e-vapor aerosols did not cause notable changes in the BALF parameter indicative of lung inflammation. Typical MS-induced changes in serum liver function and erythrocyte parameters were not observed in the e-vapor aerosol groups. While reduced blood lymphocyte counts were observed in the male PG/VG/F-High and PG/VG/N groups, the effect was comparable or significantly lower than those in the MS group. In summary, chronic exposure to flavor e-vapor aerosols under the tested condition did not result in notable chronic toxicity or lung inflammation.