Water pollution is the contamination of certain bodies of water, such as rivers, oceans, and lakes which may ultimately lead to the harm of organisms living in the surrounding environment. Throughout the world, water pollution is the main cause of death and disease, claiming approximately 14,000 lives daily. Water is classified as polluted when it is no longer able to provide a use for humans (i.e. drinking water, water for bathing), or when it is unable to support the life of organisms living in and around the source of water, such as fish and aquatic plants. There are many causes of water pollution, which attribute to the complexity and severity of the situation as a whole.
Sewage systems often become one of the major sources for water pollution. Disease causing pathogens thrive in situations where sewage water is treated inadequately. For example, in underdeveloped countries, sewage systems may not be built to the standards of more prosperous societies. Sewage pipes may be leaky, and ultimately may cause sanitary sewer overflows, which discharge contaminated sewage into the environment. This could be caused by heavy rainfall, and may carry the sewage into storm-water drains, which eventually empty into rivers and oceans, thus polluting the water harming aquatic life.
Water may also become polluted as a result of littering by humans or other factors. Waste may be disposed of in rivers or also thrown into storm-water drains, thus releasing chemicals and pollutants from certain objects, such as detergents or even cosmetic products. Littering on beaches may also contaminate ocean water, due to high tides collecting rubbish and waste left on the beaches by tourists and residents. Another large factor that contributes to water pollution is oil spills. Large oil tankers may secrete oil into the ocean due to storms or leaks. This becomes highly damaging to life not only in the ocean but also to other organisms such as birds, which become poisoned due to their relentless attempts at ridding themselves of the oil trapped in their feathers.
Pollution, however, is not always caused by unnatural factors. Flooding may also attribute to the pollution and contamination of water. Heavy rain and an overflow of water in rivers may cause dirt erosion from the banks, causing pollution from a surplus of sediment. Storms may contribute by tearing down trees and plants, causing debris to enter rivers, eventually contaminating water with bacteria from pieces of bark or other debris.