This study investigates the bioavailability and toxicological risks of microplastics to marine mussels, specifically focusing on the adsorption and transfer of pyrene, a polycyclic aromatic hydrocarbon (PAH). Microplastics, particularly polyethylene (PE) and polystyrene (PS), were found to adsorb pyrene in a time- and dose-dependent manner. The contaminated microplastics were then used to expose mussels, leading to the accumulation of pyrene in tissues, especially in the digestive glands and gills. Histological analyses revealed the presence of microplastics in various tissues, and biochemical analyses showed significant immunological, genotoxic, and oxidative stress responses in mussels exposed to both virgin and contaminated microplastics. The study also employed a DNA microarray platform to analyze gene expression changes, identifying several pathways and genes involved in the cellular responses to microplastics. The results highlight the potential risk of microplastics as a source of chemical exposure and their toxicological implications, emphasizing the need for a comprehensive risk assessment approach.This study investigates the bioavailability and toxicological risks of microplastics to marine mussels, specifically focusing on the adsorption and transfer of pyrene, a polycyclic aromatic hydrocarbon (PAH). Microplastics, particularly polyethylene (PE) and polystyrene (PS), were found to adsorb pyrene in a time- and dose-dependent manner. The contaminated microplastics were then used to expose mussels, leading to the accumulation of pyrene in tissues, especially in the digestive glands and gills. Histological analyses revealed the presence of microplastics in various tissues, and biochemical analyses showed significant immunological, genotoxic, and oxidative stress responses in mussels exposed to both virgin and contaminated microplastics. The study also employed a DNA microarray platform to analyze gene expression changes, identifying several pathways and genes involved in the cellular responses to microplastics. The results highlight the potential risk of microplastics as a source of chemical exposure and their toxicological implications, emphasizing the need for a comprehensive risk assessment approach.