Bangladesh’s shallow tube wells, dug from the 1970s onward to escape microbe-laden surface water, turned out to tap groundwater laced with naturally occurring arsenic. It is still one of the largest mass poisonings of a population in history.
The good news is that exposure is falling. When the national Multiple Indicator Cluster Surveys tested the water people actually drink, the number of people above the World Health Organization’s guideline of 10 µg/L fell from 46.7 million in 2009 to 27.5 million in 2019.
17.4 million
people still drank water above Bangladesh’s own national standard of 50 µg/L in 2019 — barely fewer than the 19.5 million a decade earlier.
That is the catch. Most of the improvement came from people moving from moderately contaminated water to safer sources. The most heavily exposed group — above the national standard, which is five times looser than the WHO guideline — has shrunk by only about 2 million people in ten years, and exposure to very high concentrations (above 200 µg/L) actually rose in Sylhet, Chattogram, Khulna and Dhaka divisions.
Chronic arsenic exposure causes skin lesions and raises the risk of bladder, lung and skin cancers, heart disease and diabetes. Because these illnesses take years to appear, today’s exposure will shape cancer rates for decades. Safe-water programmes now need to target the most contaminated and least served areas rather than the easiest-to-reach households.