A screening-level human health risk assessment for microplastics and organic contaminants in near-shore marine environments in American Samoa

Solid waste disposal is a growing concern among Pacific Island nations. With severe limitations in land area, in combination with the lack of reuse or recycling options, many near-shore marine ecosystems across Oceania are highly impacted by locally derived marine debris, including plastics, microplastics and associated chemical contaminants. In order to catalyze improved solid waste management and plastic use policies, the potential ecological and public health risks must be clearly identified and communicated. Using an ecological risk assessment framework, potential risks to marine ecosystems and human health are explored by quantifying microplastics and organic contaminants in 4 study sites located in Tutuila, American Samoa. Results of sampled near-shore marine waters, marine sediments and molluscs indicate that microplastics are unevenly distributed in the marine environment, with the highest concentrations detected in marine molluscs (e.g. average of 15 and 17 particles per organism, the majority of which were microfibers identified as polyethylene terephthalate). These invertebrates also have the highest environmental concentrations of organic contaminants, including phthalates, pesticides and PCBs. However, based on estimated rates of invertebrate consumption, the risk of adverse impacts to human health are likely to be low. Regardless, future studies are recommended to better understand the environmental partitioning of microplastics in dynamic near-shore marine environments, as well as the specific pathways and consequences of the physical and chemical impacts of microplastics on marine species populations and overall marine ecosystem health.