In West Bengal, India, water is mostly supplied from rivers. Groundwater comes from deep tube wells, which are few in number. Because of the low quantity of deep tube wells, the risk of arsenic poisoning in West Bengal is lower. According to the World Health Organization, "In Bangladesh, West Bengal (India), and some other areas most drinking-water used to be collected from open dug wells and ponds with little or no arsenic, but with contaminated water transmitting diseases such as diarrhea, dysentery, typhoid, cholera, and hepatitis. Programmes to provide 'safe' drinking-water over the past 30 years have helped to control these diseases, but in some areas they have had the unexpected side-effect of exposing the population to another health problem—arsenic."