Water pollution can occur directly, when contaminated runoff enters lakes and streams, and through atmospheric pollution that results in acid rain. Water that has been polluted may be unsafe for human use or consumption and may damage entire ecosystems.
Agricultural and industrial operations often produce hazardous chemicals that may enter into the water cycle through runoff. Fertilizers, pesticides and even antibiotics used on livestock all have the potential to pollute groundwater, lakes and streams and even ocean water in coastal areas. Other industrial sources of water pollution include oil spills and other accidents resulting in chemicals being directly introduced into a body of water.
Water pollution may affect bacteria levels, resulting in an environment that is unable to sustain life. Fertilizers used in agriculture have been responsible for the creation of hundreds of aquatic dead zones in coastal areas. Plastics and other non-biodegradable materials are also introduced to rivers, streams and oceans through non-point pollution. Phenomena such as the Great Pacific Garbage Patch are also a result of water pollution. The garbage patch, sometimes called the Pacific Trash Vortex, is the result of litter, debris and other materials that have been introduced to the ocean, where they have formed a vast collection of debris.