Microplastics in coastal and marine environments: A critical issue of plastic pollution on marine organisms, seafood contaminations, and human health implications

• Microplastic is one of the most prevalent environmental pollutants globally. • Microplastics pose significant threats to coastal and marine organisms. • Aquatic organisms reflect the physiological disruption of microplastics. • Fish and shellfish are among the most consumed seafood worldwide. • Exposure to microplastics exacerbates the onset of human health. Plastic has quickly become one of the world's most prevalent environmental pollutants. Population growth has only amplified the demand, resulting in 430 million tons of plastic produced annually, with 11 million tons ending up in our oceans. Without intentional intervention, plastic waste in the oceans is expected to triple, posing severe risks for the aquatic ecosystems, animals, and humans dependent on these waters. As plastic accumulates in oceans and other water environments, the non-biodegradable particles break down into micro- and nano-plastics, invading coastal and marine organisms and causing considerable physiological and morphological damage. This is especially concerning for the millions of people globally who rely on seafood as a primary protein source and depend on healthy oceans for their livelihoods. Among marine species, filter-feeding bivalve mollusks like oysters, mussels, and scallops play an essential role as bioindicators of water quality and ocean health. Yet, marine mollusks are also the most consumed raw seafood, meaning that any toxins or pollutants that accumulate within their bodies—including microplastics—are directly ingested by humans. With increasing microplastic pollution, mollusks are ingesting more of these particles, posing a direct risk to human health. This article critically summarizes the history and classifications of microplastics and their effects on fish and shellfish species, including how oxidative stress and antioxidant levels in these organisms respond to an increase/decrease in microplastic exposure. Additionally, it explores the potential human health impacts of consuming microplastic-burdened seafood, particularly shrimp, clamps, crabs, and oysters, and other risks for human and environmental health.