## 4 Discussion
The results show a highly significant positive correlation between the IL-8 expression increase and the endotoxin concentration in each sample, while no significant correlation with the PM\({}_{10}\) mass was observed. These findings align with the literature, in which the negative impact of particulate matter on human health is more closely associated with the chemical and biological composition of PM than its mass. Endotoxins have an inherently inflammatory nature and are powerful activators of the NLRP3 inflammasome complex, which, through caspase 1 activation, is responsible for the release of pro-inflammatory cytokines and interleukins. [PERSON] et al. [39] evaluated the inflammatory potential of airborne endotoxins emitted from composting plants, finding significantly elevated concentrations near the plants, as well as in surrounding areas. Cells exposed to bioaerosol extracts released high amounts of IL-8 and IL-6, which correlated significantly with endotoxin levels. When the cells were treated with Polymycin B (a specific endotoxin inhibitor), the pro-inflammatory effect was inhibited, and the cytokine stimulation was found to be higher for airborne endotoxins than for commercially purified _E. coli_ endotoxins. A significant variation in gene expression was found when considering the types of plants. Normally, air and bioaerosol characterization in these environments reveals different compositions of airborne microbial communities in various plants and specific operational areas within them. This leads to heterogeneity in the overall PM composition and, consequently, in the resulting biological effects. A previous study conducted on similar plants revealed significantly higher microbial contamination in the air in organic waste treatment plants, with a prevalence of bacterial species in biomass entry and storage areas compared to plants treating different matrices, where the fungal component predominated [17; 40]. Therefore, gene expression, cytotoxic activity, and PM concentration and endotoxins seem to differ significantly based on the plant type or specific operational phase, rather than the PM fraction. Specifically, IL-8 was significantly induced by PM from composting plants, which appear to produce more inflammatory PM, while XPF was significantly down-regulated by PM from lignocellulosic matrix plants, where ERCC1 significantly increased, indicating a PM that seems to impair genomic damage repair mechanisms more than others. Although full-scale biomass treatment plants are rarely assessed for genotoxic potential, this study presents several limitations. One of the main issues is the lack of characterization of the biological and chemical components of the particulate matter. While the identification of individual agents could provide valuable insights, the objective of this study was to assess the genotoxicity of the complex, multi-component pollution mixtures typical of the waste treatment methods examined, rather than to isolate a specific microbial or chemical signature. Another limitation is the inability to provide a mechanistic interpretation of the observed genotoxic effects, which would be desirable in future research. This study focused on organic extracts of particulate matter, which have been shown in the literature to have the strongest association with genotoxic effects. However, we cannot rule out the potential contribution of aqueous extracts, typically examined for reactive oxygen species (ROS) activity. Future research could include parallel sampling streams, one dedicated to extract-based genotoxic assays and another reserved for molecular endpoints. Furthermore, the analytical techniques employed in this study could be expanded. Incorporating methods such as RNA sequencing or western blotting could provide complementary evidence. Additionally, validating the findings across multiple cell lines would strengthen the reliability of the data.