It is of great significance to examine the adverse effects of nanoparticles (NPs) on the environments and human health. In the present study, we have investigated the toxicological effects of NPs on two distinct strains of yeast, S. cerevisiae and S. pombe, in aqueous solutions of NaCl. The positively charged NPs of 100-nm diameter were more significantly adhered on (and uptaken by) a negatively charged cell of every yeast strain at lower ionic strength. Every yeast in 150-mM NaCl solution (high ionic strength) showed the cell viability of more than 80% even after exposure to 100-mu g/mL NPs, whereas in 5-mM NaCl solution (low ionic strength) it exhibited zero cell viability at 25-mu g/mL NPs. Interestingly, the dead cells in 5-mM NaCl solution containing 6.25-12.5 mu g/mL NPs exhibited about 2-fold amount of cellular adhesion/uptake of NPs, compared with the corresponding live cells. The ratio between the saturated amounts of the cellular adhesion/uptake of NPs in 5-mM and 150-mM NaCl solutions for S. cerevisiae was about eighteen times greater than that for S. pombe. This behavior of S. cerevisiae is explained in part by the larger ratio between the zeta potentials of a cell in 5-mM and 150-mM NaCl solutions. (C) 2020 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.