Plastics are ubiquitous across the globe and contain a wide array of chemical additives that enhance or impart specific physical and chemical properties to the finished products. However, at the end of their lifecycle, plastics frequently enter the environment as waste due to improper disposal or inadequate waste management practices. Mismanagement leads to the release of chemical additives into various environmental matrices, resulting in widespread contamination. These chemicals can get released from plastic materials throughout their lifecycle, starting from their virgin form during production to their degradation at end of life. The chapter explores pathways through which these chemical additives are released into the riverine and marine environments, emphasizing contamination and interaction with various ecosystems. This chapter also comprehensively lists potential health impacts posed by these chemicals associated with plastics. The aim is to provide readers with a thorough understanding of the types of chemical additives used in plastic products, their release mechanisms, and their impact on environmental and human health.