Characterization of aerosols produced during shampoo use and harmful chemicals in shampoo aerosols

To declare a shampoo toxicologically safe, one should evaluate the hazards posed by the inhalation of aerosols produced during its use. Herein, tap water was sprayed into a shampoo-filled plastic container to investigate the formation of shampoo aerosols and the possibility of their inhalation. The aerosols thus obtained had higher mass concentrations (geometric mean = 5779 μg m^-3 (PM₁₀) and 2249 μg m^-3 (PM_2.5)) than water aerosols (geometric mean = 927 μg m^-3 (PM₁₀) and 476 μg m^-3 (PM_2.5)). In particular, shampoo aerosol particles with an aerodynamic diameter of 2.5 μm, which can penetrate the alveoli when inhaled, had the highest mass concentration (geometric mean = 2000 μg m^-3). The volatile organic compounds contained in shampoo aerosols featured alcohol and ether groups attached to dodecane and tetradecane backbones; these compounds were generated by the thermal decomposition of surfactants (i.e., lauryl and laureth sulfates) during instrumental analysis. The acquired data suggest that inhalation exposure and chronic inhalation toxicity evaluations should be performed for various shampoo usage conditions to ensure inhalation safety.