Atmospheric microsized particles producing reactive oxygen species can pose a serious health risk for city residents. We studied the responses of organisms to microparticles in 255 healthy volunteers living in areas with different levels of microparticle air pollution. We analyzed the distribution of microparticles in snow samples by size and content. ELISA and flow cytometry methods were employed to determine the parameters of the thiol-disulfide metabolism, peroxidation and antioxidant, genotoxicity, and energy state of the leukocytes. We found that, in the park areas, microparticles with a size of 800 μm or more were predominant (96%), while in the industrial areas, they tended to be less than 50 μm (93%), including size 200–300 nm (7%). In the industrial areas, we determined the oxidative modification of proteins (21% compared to the park areas, p≤0.05) and DNA (12%, p≤0.05), as well as changes in leukocytes’ energy potential (53%, p≤0.05). An increase in total antioxidant activity (82%, p≤0.01) and thiol-disulfide system response (thioredoxin increasing by 33%, p≤0.01; glutathione, 30%, p≤0.01 with stable reductases levels) maintains a balance of peroxidation-antioxidant processes, protecting cellular and subcellular structures from significant oxidative damage.