Abstract Background Micro- and nano-plastics (MNPs) and environmental pollutants, including plastic-associated chemicals, are widespread in the outdoor but also, importantly, indoor environments 1 to 4, where humans spend the majority of their time 5. Exposure to all of the above can occur via inhalation, with children at extra risk of negative health impacts 6. Previous work has focused on toxicity testing of individual chemicals, however real-life scenarios are likely to involve mixtures and chemicals adsorbed to MNPs 7. Methods Four different test substances were used: a textile dye (DB 373), flame retardant (BDE-47), heavy metal (in the form of CuCl2) and hydroxylated polystyrene (PS) spheres. Lung epithelial cells (A549) and macrophages (RAW 264.7) were exposed to each chemical alone and in combination for 24 h. Analysis included measurements of cell viability, cytotoxicity, cytokine release and intracellular reactive oxygen species (ROS) production. Mixtures were also assessed for size distribution and acellular ROS production, using DLS and FRAS analysis, respectively. Results Results showed a statistically significant decrease in cell viability occurred for each test substance individually and a decrease or increase in effect was observed when combined as a mixture, dependent on mixture composition. For example, a significant increase in IL-8 was seen for a mixture containing PS, DB 373 and CuCl2. Conclusions Variation of observed effect compared to expected additive effect suggests that mixtures may be acting synergistically or antagonistically. This work suggests that mixture toxicity should gain more focus and be relied upon more than just toxicity assessment based on individual chemical data.
Meadows et al. (2026) studied this question.