Up to half the residents of Bangladesh, some 77 million people, are being exposed to high levels of naturally occurring arsenic in what the World Health Organization (WHO) calls the “largest mass poisoning of a population in history.”
The problem reaches back 30 years, when 9 million narrow, shallow tube wells were dug throughout the country to prevent water-borne diseases caused by contaminated surface water. In 1993 the well water was discovered to contain dangerously high quantities of arsenic from geologic sources. A study involving 10 different districts (Environ Int 2002;27:597-604) determined that 94% of urine samples tested contained arsenic above the normal level, as did 95% of nail samples and 96% of hair samples.
The International Agency for Research on Cancer considers arsenic a human carcinogen. Arsenicosis can cause skin cancer and cancers of the bladder, kidney and lung, as well as diseases of the blood vessels and legs and feet, hypertension and reproductive disorders (see CMAJ 2002;166[1]:69).
The crisis has led to intense research into water decontamination techniques, which includes development of the STAR (Stevens Technology for Arsenic Removal) water-treatment process. This inexpensive filtration system involves mixing 3.8 g of an iron-sulphate mixture with a small quantity of calcium hypochlorite in drinking water, and then filtering it through sand.
WHO water expert Jamie Bartram says it remains to be seen whether clean water will eliminate any long-term after-effects of arsenicosis. — Barbara Sibbald, CMAJ
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Figure. The grim reality of arsenicosis Photo by: WHO