Arsenic contaminated tube well water was first detected in Bangladesh in early 1990s. The arsenic comes from naturally arsenic-rich material delivered by the region's river systems, deposited over many years to make up the land of Bangladesh. Arsenic contamination is not caused by tube wells, or by irrigation or application of fertilizers.<br> Today, although 98 per cent of the population uses an improved drinking water source the safe water coverage of Bangladesh is 86 per cent because of arsenic contamination.