Water pollution is a broad term that describes any kind of contamination of bodies of water such as rivers, lakes or wetlands with substances that can pose threats to human health or the natural environment.
Such pollution is a major source of death and disease worldwide, especially in developing nations. Even in wealthier nations where piped water supplies mean that water pollution poses fewer direct threats to human health, many lakes and rivers are polluted.
Pollution can come from a wide variety of sources and these sources are often categorized as either point source or nonpoint source. Point source pollution has single identifiable source, whether it is a wastewater pipe or a ship dumping waste. Nonpoint source pollution comes from water runoff picking scattered pollutants off the ground.
Examples of water pollution include: chemical or oil spills; industrial waste, fertilizers and pesticides that run off agricultural land into rivers; sewage that enters rivers and seas, heavy metals that leach out of the ground, or plastics that degrade in water.
Other forms of water pollution include the presence of microbes that can harm human health (see Water-borne Diseases), or an an excess of suspended particles that can block light and harm aquatic life.
These combined forms of water pollution pose grave threats to human health. A 2010 report by the UN Environment Program said that more people now die from contaminated and polluted water than from all forms of violence including wars.
The report stated that two million tons of waste — estimated to equal two or more billion tons of wastewater — will enter rivers and seas every day. This can both spread diseases to humans and damage key ecosystems such as coral reefs and fisheries.
Where fresh water is scarce, pollution can become an even bigger problem as people are forced to make use of contaminated supplies. The UN estimates that by 2025, some 1.8 billion people will live in areas where water is scarce.
Water pollution is more likely in places where environmental protection laws are weak or poorly enforced, where infrastructure is lacking, and where there is a little awareness of the dangers of allowing harmful substances to enter water bodies such as lakes or rivers.
Most household wastewater generated in less-industrialized countries is released untreated into water courses. This is a major contributor to the nearly two million deaths of children under the age of five every year from water-borne diseases.
Agricultural land is another major source of water pollution, including pesticides, fertilizers and animal waste. In 1995, when about 20 million gallons of waste spilled from a pig farm in North Carolina, United States, the sewage killed thousands of fish in local rivers and polluted drinking water for nearby communities.
The best ways to limit risks from water pollution are to prevent dangerous contaminants from entering water, and – if this cannot be avoided – to treat polluted water to remove the threats before people are exposed to them.
As many of the main sources of water pollution are forms of waste — such as household, industrial and agricultural waste — legislation, standards and infrastructure for waste management play a key role in reducing the threat. These vary greatly from country to country, however.
When clean drinking water is not available through piped supplies it can be treated at the point of use with chemicals, filters or other approaches.
A big challenge in reporting on water pollution is that it is often difficult to say for sure where the pollution comes from, especially for nonpoint source pollution.
Good sources of information for journalists include the many different UN agencies whose work relates in some way to water. UNWater exists to improve links between these agencies. Its website includes factsheets, relevant publications and other information for journalists.
The UN has also initiated a ten-year program called Water for Life, which aims to improve communication about water and has many activities aimed specifically at improving journalistic reporting.
World Water Week is an annual conference in Stockholm, Sweden – and is a rich source of stories. The conference’s website has an online press room with regional factsheets, statistics and graphics to help journalists.
Another source of stories and contacts is Water-L, an email-based mailing list for news and announcements about water policy around the world.
Other sources of news, contacts and story ideas include Circle of Blue, an international network of journalists, scientists and communicators who share information publish Water News, which is updated daily online.
Lastly, National Geographic has gathered a good list of organizations working on water pollution, which journalists can turn to as sources.