A tragic example of arsenic poisoning is in Bangladesh. Around 1980, international organizations and the Bangladesh government began installing tubewells to help the people exposed to harmful drinking water contaminated with pathogens such as E. coli present in surface waters contaminated with sewage. Drilling wells to provide adequate drinking water was a great idea to provide clean drinking water. However, unfortunately, it was not known that the groundwater in Bangladesh contains naturally occurring arsenic, and the water was not tested for arsenic. The transition from drinking surface water to drinking well water led to the poisoning of up to 50 million people in Bangladesh who were exposed to unsafe levels of arsenic from tubewells. Over time, exposure to arsenic causes cancer, decreased reproduction rates, reduced intelligence in children, and arsenicosis (a group of skin conditions including skin cancer associated with arsenic exposure). The problem of arsenic poisoning in Bangladesh was not recognized until 1993, when it was tested for in northern Bangladesh. Alternative sources of arsenic-free drinking water have subsequently been provided to the people. However, arsenic poisoning is still a public health problem in Bangladesh today. 

Ahmad, S. A., Khan, M. H., & Haque, M. (2018). Arsenic contamination in groundwater in Bangladesh: implications and challenges for healthcare policy. Risk management and healthcare policy, 11, 251–261. https://doi.org/10.2147/RMHP.S153188