Arsenic contamination in Bangladesh ground water has been called perhaps the most widespread mass poisoning in history, exposing at least 10 million people to arsenic levels that cause eye disorders, skin lesions such as gangrene, and cancer. Ironically, the population's massive exposure to arsenic resulted from efforts begun in the 1960s by international aid organizations to reduce exposure to pathogens in drinking water by sponsoring the sinking of millions of shallow tube wells into underground aquifers. However, not until 1993 did health experts realize that the sediments found throughout the country contain high levels of natural arsenic that leach into ground water. In a paper delivered Thursday at the American Geophysical Union meeting in Boston, postdoctoral fellow Mohammed Riajul Islam and Rojstaczer described the results of their analyses of samples of ground water, surface water and soil in five locations throughout Bangladesh. The scientists' objectives were both to measure surface water arsenic levels and to explore possible geologic and geochemical reasons for varying arsenic levels in order to guide possible re-siting of wells to reduce arsenic levels.
Some surface waters come from ground water that has leached through soils highly laden with arsenic.
And some surface waters received drained irrigation return water that originally came from pumped ground water. The scientists found surface water arsenic levels greater than WHO drinking water standards at most of the sites, the highest being176 micrograms per liter in surface water in Rajarampur, near the Indian border. WHO guidelines specify arsenic levels no higher than 10 micrograms per liter. Ground water arsenic levels were highly variable in the scientists' samples, ranging from less than one microgram per liter to greater than 2,000 micrograms per liter. The Duke hydrologists also tested for the presence of other metals, and found aluminum levels in one area that was 10 times higher than WHO guidelines.