Since the mass production of polymers 80 years ago, inexpensive manufacturing techniques have been optimised, and a plethora of lightweight, durable, inert and corrosion-resistant plastics found numerous practical applications replacing wood, metals, skin and other natural materials. Global plastic production in 2016 was estimated at 335 million metric tones. Plastics very quickly spread worldwide and their disintegration into microplastic in the aquatic and the marine environment became an emerging environmental problem. In the last 40 years the world production of plastic resins increased 25-fold, while recovery of the waste material remained below 5%. It is estimated that between 8-12 million metric tons of plastic waste enters the oceans every year; eventually break down into small particles. These tiny plastic particles—known as microplastics—are entering the food chain and being fed into marine species which are consumed by humans. The question inevitably has been what toxic damage they are infering to biological aquatic and marine species and if consumed whether they could harm cells and tissue in the human gut. Numerous studies have been commissioned and their results revealed that microplastic pollutants are widespread and ubiquitous within the marine environment. Also, they adher to waterborne organic pollutants (adsorbed on the large porous surface) and are leaching plasticisers (stabilizers, plasticizers, flame retardants, colours) which are considered toxic. The harm to biota is much greater than intially thought because they are ingested and absorbed in the digestive system and tissues of marine biota. Also, microplastic toxicity increases because they can absorb other dissolved toxic substances from the aquatic environmen. Finally, their persistence and bioaccumulation can be dangerous to marine species. The European Marine Strategy Framework Directive and the United States Microbead Free Waters Acthave projected goals to protect the marine environment from microplastic pollution. In the last decade, studies revealed high concentrations of microplastics in marine species that inevitably raised questions on microplastics in seafood (fish and shellfish). High consumption in some countries of seafood raised concerns about the potential effects on human health. Scientists agree that there are at present major challenges and gaps in our understanding of toxic mechanisms and controversial findings on health risks from consumption of seafood. So, there is a need for more research regarding the level of potential exposure and associated health risk to micro- and nano-sized plastics. At present, there is no enough knowledge for the detailed toxic mechanism and metabolism. Also, toxciological information available about the fate of microplastics in the human body following ingestion through contaminated food consumption is lacking.
http://chem-tox-ecotox.org/microplastics-marine-species-human-cons-march-2019/