Abstract.Global plastics production reached 368 million metric tons in 2019. Exceptional properties, such as low cost, lightweight, high strength and durability, make plastics suitable for manufacture on a wide range of useful products and industrial materials. But in the last decades, plastics have become the most dominant form of terrestrial and aquatic waste with devastating environmental consequences. It has been estimated that at least 5 trillion plastic particles weighing above 268,000 tons have been discarded into the oceans. The UNEP estimated 4.8–12.7 million metric tonnes of plastic are introduced to the oceans annually (2017). However, the high demand and inappropriate disposal of plastic materials have led to their dispersion and accumulation in the natural environment. During the COVID-19 pandemic, the worldwide production and disposal of plastic face masks and other medical materials have added to the vast thrown away waste. with most important sources in big cities’ municipal waste. Once plastic debris go into the terrestraial, marine and ocean environment, they break down into microplastics (<5mm) by photolytic, mechanical and biological degradation. Further, there is additional fragmentation from larger to smaller size nanoplastics (< 25 µm) accumulating continuously in the marine environment and in tissues of marine species. Micro- and nanoplastics pollution has been a cause of concern among toxicologists for their risk potential for filter feeders consuming plastic waste. Plastic fragments are persistent and due to their micron sized particle are mistaken as food and ingested by a range of marine biota (corals, zooplanktons, sea urchins, lobsters, mussels, fish, etc) and ultimately get transferred to higher trophic levels. Μicro- and nanoplastics (MNPs) are increasingly found in the human food system with potential to cause harmful metabolic effects to human health. Toxicologists and risk assessment specialists try to estimate the toxicological impact on human health, although it is difficult to assert and scientists suggest that there is urgent task for further research. This review presents a large number of toxicological risk assessment studies from exposure to MNPs through in vitro (cellcultures) and in vivo experiments (rats, mice, etc) used in toxicological investigations. Knowledge of direct human health implications are lacking. Epidemiological risk assessment is focusing on inflammation, oxidative stress and other cytotoxic effects at realistic environment concentrations of plastics, but accurate risk to human health is difficult to validate.
Risk Assessment and Toxicological Research for Microplastics and Nanoplastics. Adverse effects to marine organisms and potential harmful implications to human health
Oct 25, 2021