Water pollution, together with loss of biodiversity, climate change, energy and socioeconomic issues, is one of the main threats and challenges humanity faces today. Human activities and human-related substances and wastes introduced into rivers, lakes, groundwater aquifers and the oceans modify the environmental water quality and make huge quantities of water unsuitable for various uses. This is the case not only for human-related uses such as drinking, bathing, agricultural irrigation and industrial production but also for terrestrial and aquatic ecosystems for which clean, fresh water is a prerequisite for life.
Water pollution is a serious problem for human health and the environment. The extent of the problem has been confirmed by many reports from UN organisations and related statistics. For example the Global Environment Outlook report (2000) produced by the United Nations Environment Programme (UNEP) included the following statistics:
. Already one person in five has no access to safe drinking water.
. Polluted water affects the health of 1.2 billion people every year, and contributes to the death of 15 million children less than 5 years of age every year. . Three million people die every year from diarrhoeal diseases (such as cholera and dysentery) caused by contaminated water. . Vector-borne diseases, such as malaria, kill another 1.5-2.7 million people per year, with inadequate water management a key cause of such diseases.
Water pollution contributes to the so-called global water crisis, because it reduces the available amount of freshwater resources for both people and ecosystems. Freshwater scarcity is already a reality in many parts of the world, not only in developing countries like India, China and many African countries, but also in countries and regions traditionally considered as water rich, such as the USA and Europe. The United Nations (UN) predicts that two-thirds of the worlds population will live in water-scarce regions by 2025. The increase in water demand, together with the increase in population in many parts of the world, but mainly the over use of water in areas like agriculture, together with water pollution and climate change are the main driving forces behind this phenomenon.