According to the World Health Organization the maximum amount of arsenic in drinking water should be limited at 0.01 mg/L (10ppb).
It has been estimated that there is close to 100 million people in developing countries exposed to dangerously high levels of arsenic in their drinking water
Bangladesh is the country most affected with arsenic poisoning of drinking water – according to the unofficial estimates every fifth well in Bangladesh has arsenic concentration above the government's drinking water standard.
According to the 2007 study over 137 million people in more than 70 countries of the world are likely affected by arsenic poisoning of drinking water.
Arsenic as a water contaminant is not being introduced into water wells by humans, but leached naturally from sediments.
There have been around 20 reported incidents of groundwater arsenic contamination from all over the world.
United States has many wells where arsenic concentrations are in excess of the Environmental Protection Agency (EPA) standard of 10 parts per billion adopted in 2001. This shouldn't really come as a surprise when you consider that around 43 million Americans depend on unregulated private wells, and that at least a quarter of wells have at least one contaminant exceeding levels considered safe by the EPA.
According to EPA arsenic is the second-most common contaminant at Superfund sites.
Symptoms of arsenic poisoning include thickening and discoloration of the skin, stomach pain, nausea, vomiting and diarrhea, vision loss as well as numbness in hands and feet. The chronic exposure to arsenic has been linked to an increased risk of diabetes and several cancers.
There are several different technologies to remove arsenic from drinking water. Among the most interesting is no doubt Subterranean Arsenic Removal (SAR). SAR removes arsenic from groundwater without using chemicals by using the principles of oxidation and filtration processes.