Occurrence, distribution, and ecological risks of microplastics in the offshore environment: a review

The indiscriminate use of plastic worldwide, coupled with inadequate disposal practices, has led to substantial accumulation of microplastics (MPs) in marine environments, with offshore regions acting as major sinks. This study reviews the current understanding of MP sources, classification, and distribution in offshore water columns, sediments and biota. It identifies terrestrial inputs as the dominant source and highlights the role of oceanic and atmospheric processes in modulating their dispersal. MPs exhibit diverse morphological and polymer profiles, with polyethylene (PE), polypropylene (PP), and polystyrene (PS) being the most prevalent polymers. Their small size, hydrophobicity, and high specific surface area promote ingestion by marine organisms, leading to bioaccumulation, oxidative stress, endocrine disruption and impairments in metabolic and reproductive functions. Furthermore, MPs may act as vectors for adsorbed hazardous contaminants, potentially amplifying ecological and human health risks. Key research priorities include addressing gaps in spatial and seasonal distribution data, lack of in situ toxicity validation, and the development of comprehensive risk assessment frameworks for combined pollutant exposures. This review aims to support targeted research and inform effective mitigation strategies against microplastic pollution in coastal-offshore ecosystems.