Arsenic poisoning is a medical condition that occurs due to elevated levels of arsenic in the body. If arsenic poisoning occurs over a brief period of time, symptoms may include vomiting, abdominal pain, encephalopathy, and watery diarrhea that contains blood. Long-term exposure can result in thickening of the skin, darker skin, abdominal pain, diarrhea, heart disease, numbness, and cancer.
The most common reason for long-term exposure is contaminated drinking water. Groundwater most often becomes contaminated naturally; however, contamination may also occur from mining or agriculture. It may also be found in the soil and air. Recommended levels in water are less than 10–50 µg/L (10–50 parts per billion). Other routes of exposure include toxic waste sites and traditional medicines. Most cases of poisoning are accidental. Arsenic acts by changing the functioning of around 200 enzymes. Diagnosis is by testing the urine, blood, or hair.
Prevention is by using water that does not contain high levels of arsenic. This may be achieved by the use of special filters or using rainwater. There is not good evidence to support specific treatments for long-term poisoning. For acute poisonings treating dehydration is important. Dimercaptosuccinic acid (DMSA) or dimercaptopropane sulfonate (DMPS) may be used while dimercaprol (BAL) is not recommended. Hemodialysis may also be used.
Through drinking water, more than 200 million people globally are exposed to higher than safe levels of arsenic. The areas most affected are Bangladesh and West Bengal. Exposure is also more common in people of low income and minorities. Acute poisoning is uncommon. The toxicity of arsenic has been described as far back as 1500 BC in the Ebers papyrus.
The roots of the arsenic crisis in the Ganges delta go back a generation to when most Bangladeshis drank water from rivers and ponds that were often contaminated by sewage. Thousands died each year from gastrointestinal diseases. International agencies such as UNICEF devised a plan to sink boreholes into the sands of the delta that covers much of Bangladesh and the neighbouring Indian state of West Bengal. Unfortunately, nobody thought to check the underground water for natural poisons until symptoms of arsenic poisoning began to emerge, first in West Bengal and later in Bangladesh. In 2000, there were more than 4 million such boreholes supplying water to 95 percent of Bangladesh's villagers.