Contamination of groundwater supply can occur as a result of natural processes as well as industry and agriculture. Probably, the most lethal and extensive groundwater pollution problem globally is actually natural in origin: the contamination of groundwater with high concentrations of arsenic. Approximately 100 million people globally are exposed to high levels of arsenic in groundwater. Nowhere is the problem more devastating than over large regions of Bangladesh and the West Bengal region of India, where millions have been poisoned by arsenic. This area is intensively irrigated, which has changed the flow of groundwater over a large region. As a result, a shallow aquifer is the source of groundwater for 35-77 million inhabitants who obtain their water from shallow tube wells.
Arsenic in Groundwater
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High levels of arsenic in this water likely derive from microbial activity that dissociates arsenic from organic material. Arsenic is highly poisonous and carcinogenic and long-term exposure to it can lead to high incidences of skin lesions, bladder, lung, skin and kidney cancer, respiratory disease, and liver and kidney disease. Because the threatened regions are heavily populated, this pollution has made millions of people sick and caused thousands of deaths each year. Even though the hydrology of the affected areas is not well understood, the solution to the arsenic contamination issue involves a combination of extensive monitoring, closing down high-concentration wells, distribution of filters and chemicals to remove arsenic from drinking water, and ultimately tapping deeper aquifers.
The following video provides an overview of the arsenic problem in Bangladesh.
Video: Bangladesh: Traces of Poison in Water (5:03)
Pollution from agricultural and industrial sources is common, although not always as lethal as arsenic poisoning. Typical sources of industrial pollution include solvents, gasoline and other hydrocarbons, paint, and heavy metals. Pollution from agricultural sources includes pesticides, herbicides, and fertilizers. Many of these pollutants are carcinogenic. Both sources of pollution can lead to the growth of toxic microbes. Agricultural and industrial runoff can deliver pollutants into groundwater systems
Human and agricultural sewage is another potential source of pollution. This pollution leads to a variety of different impacts on health all the way from gastrointestinal illness to, in severe cases, cholera, typhoid, amoebiasis, giardiasis, and E. coli.