Well water contaminated by arsenic in Bangladesh is considered one of the most devastating public health crises in the world. Almost a quarter of the country’s population, an estimated 39 million people, drink water naturally contaminated by this deadly element, which can silently attack a person’s organs over years or decades, leading to cancers, cardiovascular disease, developmental and cognitive problems in children, and death.
Well water contaminated by arsenic in Bangladesh is considered one of the most devastating public health crises in the world. Almost a quarter of the country’s population, an estimated 39 million people, drink water naturally contaminated by this deadly element, which can silently attack a person’s organs over years or decades, leading to cancers, cardiovascular disease, developmental and cognitive problems in children, and death. An estimated 43,000 people die each year from arsenic-related illness in Bangladesh.
To avoid arsenic contamination, many Bangladeshi households access water via private wells drilled to 300 feet or less, beneath impermeable clay layers. Such clay layers have been thought to protect groundwater in the underlying aquifers from the downward flow of contaminants. However, a study published in Nature Communications this week suggests that such clay layers do not always protect against arsenic, and could even be a source of contamination in some wells.
Clay layers had previously been suspected of contaminating groundwater with arsenic in parts of Bangladesh, the Mekong delta of Vietnam and the Central Valley of California, but the new paper provides the most direct evidence so far.
“Our findings challenge a widely held view, namely that impermeable clay layers necessarily protect an aquifer from perturbation,” said Alexander van Geen, a research professor at Columbia University’s Lamont-Doherty Earth Observatory who has been studying arsenic contamination of drinking water for two decades. “In this context, we show from several different angles — failed attempts to lower local exposure, high-resolution drilling, monitoring, and groundwater dating — that this is actually not the case for groundwater arsenic, because distant municipal pumping can trigger remotely the release of arsenic below such a clay layer.”
Read more at Earth Institute at Columbia University
Image: Workers install a monitoring well near the study site in Bangladesh. (Credit: Rajib Mozumder)
