<p>  </p> <p>Inhalation is a primary route of environmental and occupational exposures. Inhalation toxicology studies have thoroughly demonstrated the efficacy and adverse effects of a large number of chemicals, metals, pharmaceuticals, and agrochemicals. With the rapid development of new technologies and emergence of prominent subpopulations, some emerging exposure issues have arisen. To better protect public health, it is necessary to address these numerous emerging issues related to inhalation toxicology including 1) exposures to complex and unknown chemical emissions generated as we resolve infrastructure needs, 2) real-world exposure scenarios such as nanoparticle (NP) mixtures that may induce unique toxicity, and 3) variations in toxicity responses that occur in vulnerable and prevalent subpopulations following exposures. We designed three aims 1) to characterize differential representative composite manufacturing emissions (CMEs) and toxicity assessment of inhalation exposure to CMEs, 2) to examine the contribution of variable iron and manganese NP components in welding fumes to pulmonary toxicity, and 3) to evaluate metabolic syndrome (MetS)-induced variations in NP-Biocorona (NP-BC) composition following inhalation and modulation of pulmonary toxicity. Overall, this proposal aimed to characterize the emerging and complex exposures occurring in the real world and elucidate the mechanisms of differential pulmonary toxicity and susceptibility associated with CMEs, different metal NP components in welding fumes, and underlying diseases such as MetS. The conclusions from this project can help to improve the application of water infrastructure repairing technology and the utilization of welding and understand the mechanism of susceptibility to NP exposure among individuals with underlying diseases. Furthermore, the findings from these evaluations have supported and improved worldwide regulation, which promotes a safer utilization of novel materials, newly developed medicines, and complex chemicals.</p>