Pollution occurs in all habitats, land, sea, fresh water and in the atmosphere, occurring when the environment cannot process and neutralize harmful by-products of human activities. Run off from fields, CSOs, pollution that finds a way into the river courses and oceans. Discarded litter that finds its way into drains, to the river and ultimately to the ocean.
There are 5.25 trillion pieces of plastic debris in the ocean. Of that mass, 269,000 tons float on the surface, while some four billion plastic microfibers per square kilometer litter the deep sea (stats taken from National Geographic)