A plastic is any synthetic or semi-synthetic material that is composed mainly of organic polymers (long chains of identical molecules that contain both carbon and hydrogen). Plastics derive their name from the fact that they are highly "plastic," that is, they feature great ease of forming into a virtually limitless range of shapes through moulding, extruding and pressing. They can also have a wide range of other useful properties, including light weight, durability, flexibility, ease of combination with a wide range of additives to adjust their properties, and low cost of production. These properties have resulted in an extremely wide range of applications and a huge volume of output at about 360 million metric tons annually.
Most plastics are still produced from chemicals derived from fossil fuels, chiefly natural gas and petroleum, although they are now increasingly being made from renewable materials, such as corn or cotton.
Because of their vast of output and the fact that most are not biodegradable, plastic solids and fine particles are accumulating in huge, and ever-increasing volumes throughout the environment, including in the soil, air, water and even in the bodies of animals, including humans. They enter and circulate in the environment in several ways, mostly by discarding plastic waste on land and in the oceans. Another important source is the fine particles created by abrasion from tires on road surfaces which enter water bodies with road runoff and also enter the atmosphere.
Plastic ultra-fine, invisible particles are ingested into the bodies of humans by inhaling air containing them, by drinking water containing them, and by eating other animals that have them in their bodies. Once inside of bodies they can enter the bloodstream and the internal organs, including the heart and brain where they will remain permanently. The long-term effects of this on public health are still unknown, but they cannot be good.