What are microplastics and why are they bad for human and planet's health?

How can microplastics choke the seas and oceans and pollute the food chain?

Microplastics are those small plastic particles that pollute our seas and oceans, they have a diameter between 330 micrometers and 5 millimeters. Their danger to human health and the environment is demonstrated by several scientific studies, the most serious damage is mainly in marine and aquatic habitats. When plastic ends up in water it dissolves into smaller fragments for various reasons, for example due to the effect of ultraviolet rays, wind, waves, high temperatures, etc. The chemical additives used during production that give the materials specific characteristics, such as flame retardants that make them more resistant to ultraviolet rays, to waterproofing, also contribute to their fragmentation.

From the 1930s to the first decade of the 2000s, world production of plastics has grown from 1.5 million tonnes to over 280 million tonnes (up 38 percent in the last 10 years). Clearly, more plastic is used, more of it is thrown, directly or indirectly into the seas, at least eight million tons per year, according to Greenpeace.

In the marine environment plastic is present in many forms, bags, packaging material, construction coatings, containers, polystyrene, ribbons and fishing equipment. It has been quantified, however, that plastic waste from land represents about 80 percent of all plastic waste in the environment. Once at sea, these substances are ingested by wildlife and even modify the food chain. About 20 percent of the marine species that end up on our tables contain microplastics. Researchers at the National University of Ireland who have fished in the North Sea for mesopelagic fish at depths between 200 and 1,000 meters in the North Sea have estimated that this percentage would rise to 73%.

According to the latest report of the United Nations Environment Programme (UNEP), each square kilometer of ocean contains on average 64,000 particles of microplastics, with significant differences in various areas of the Planet, for example in South-East Asia the level is 27 times higher than in other countries. The Mediterranean is one of the most polluted seas in the world, here is concentrated 7% of the microplastics at a global level, in addition, five oceanic areas (called gyres) have been identified where, due to the currents, accumulate the largest amounts of waste.

For this reason, UNEP has placed the problem of plastics in the seas and oceans among the six most serious environmental emergencies. If we don't act now, by 2050 there will be more plastic than fish in our seas.

Fortunately there are different laws that each state has introduced to solve the problem.
In December 2015, President Barack Obama signed the Microbead-Free Waters Act 2015, prohibiting cosmetic manufacturers from adding small plastic beads into "rinse-off" products such as toothpaste and skin creams. As for other initiatives, there are several local laws in the United States that each state or city has decided to introduce.
In the Old Continent, the United Kingdom has introduced the same ban by extending the ban on adding microplastics to all cosmetic products.
Also China, the world's largest plastic recycler, has decided to take serious steps by blocking the import of plastics from the rest of the world to focus on domestically produced plastics and by blocking the import of 24 materials, including plastics, paper, textiles and some metals, with the aim of increasing domestic recycling to 350 million tons per year.
Other countries such as South Africa, Eritrea, Rwanda, Kenya, have banned the use of plastic bags. Even India, where the problem of plastics feeds illegal burning, has banned the production of disposable plastic, starting from New Delhi.