Airborne micro- and nanoplastics are widely spread and pose a risk to human health. The effects of virgin (v) and home oxidised (ox) nano- and micropolystyrene (nPS/mPS) (0.1 and 1 µm) were studied on the human alveolar cells (A549). Ox-nPS/mPS, simulating photoaging, allowed effects due to environmental wear to be assessed. Cellular uptake was quantified using FITC-functionalised nPS/mPS, while cytotoxicity, changes in the acidic compartment, ROS production, mitochondrial function and DNA damage were assessed to study the effects of internalised v- and ox-nPS/mPS. The uptake was dose-dependent and very fast, since, at the lowest dose, 20.8% and 21.8% of nPS and mPS, respectively, were internalised after 1 h. Compared to v-, significant ROS increases, DNA damage and mitochondrial impairment were observed after exposure to ox-nPS/mPS. The enhancement of effects due to environmental aging processes highlighted the true potential impact on human health of these airborne pollutants.