It is a tragedy that there are still 1.5 billion people on this earth has limited access to drinking water. Most of the people are from the developing countries. Another 1.5 billion people are suffering from gastrointestinal diseases due to water-carried pathogens every year. About 3 million people die each year due to gastrointestinal diseases. Arsenic contaminated drinking water is consumed by 50 million people. Five million people are drinking fluoride. Even one million people are consuming lead due to distribution pipes. These pictures are all from the developing countries. In 2002, three-fourth of our total population (72% of the rural population and 82% of the urban population) have the access to safe water. Our focus is on arsenic, fluoride, pesticides, manganese and cyanobacteria.