The escalating accumulation of microplastics in the environment has emerged as a critical global issue, with significant implications for ecosystems and human health. Among the most prevalent and hazardous types are polystyrene microplastics (PS-MPs), widely derived from food packaging, insulation materials, and disposable consumer products. Due to their durability, low density, and resistance to degradation, PS-MPs are persistent pollutants that fragment into micro- and nanoplastics, infiltrating water, air, soil, and the food chain. Recent studies have confirmed their presence not only in diverse environmental matrices but also in human tissues, including the blood, lungs, liver, brain, and placenta. These particles have been shown to induce cellular stress, disrupt gene expression, alter microbiota, and trigger inflammatory and oxidative responses. This review provides a comprehensive overview of PS-MPs, highlighting their environmental distribution, exposure pathways, organ-level accumulation, and toxicological mechanisms. It also explores the analytical methods used for detection, such as Raman spectroscopy, FTIR, and pyrolysis-GC/MS. By identifying current knowledge gaps and future research priorities, this work underscores the urgent need for standardized methodologies and interdisciplinary strategies to assess, monitor, and mitigate the impact of PS-MPs on public health and the environment.