On the streets of Dhaka, horns honk as a sea of motorists in cars and buses, on motorbikes and rickshaws, surges forward. Women in saris the color of mangoes and bright yellow jackfruit walk along the road beside men wearing loose-fitting shirts called kurtas. The spicy aroma of cooking chili peppers and ginger wafts from the restaurants and canteens.
Dhaka, with over 16 million residents, is the vibrant capital of Bangladesh. This nation of magnitudes, named after the Bengal tribe that inhabited it 3,000 years ago, has one of the longest beaches, largest mangrove forests and highest populations in the world. Bangladesh currently ranks as the seventh most populous country on the planet, with an estimated 160 million people crowded into an area the size of Iowa.
A health calamity of almost unimaginable proportions has been brewing in Bangladesh and elsewhere in southern Asia — in parts of India, Vietnam and Cambodia. An estimated 100 million people are being exposed to unsafe levels of arsenic in their drinking water. The World Health Organization has called the situation in Bangladesh “the largest mass poisoning of a population in history.”
University of Delaware doctoral student Md. Mahfuzur Khan, a native of Jamalpur in northcentral Bangladesh, is intent on gaining the knowledge he needs to help address the crisis.
“I want to pursue a degree that will help me to provide safe water to the people,” says Khan. “That is my primary motivation.”
Khan, who received his bachelor's and master's degrees from the University of Dhaka, is now pursuing a doctorate in hydrogeology at UD under the guidance of Holly Michael, assistant professor of geological sciences in the College of Earth, Ocean, and Environment. Michael, a leading expert in the field, is a member of a multi-university team working to assess the sustainability of Bangladesh's drinking water supply.
A flood of challenges — from water — swirls around Bangladesh. Monsoons inundate much of the country from June to October, and rising sea levels threaten low-lying areas. Some climate models predict that by 2050, an estimated 18 percent of the country's coastal area will be under-water, and 20 million people will be displaced from their homes.
Rivers such as the great Brahmaputra and Ganges and their tributaries crisscross the land, flowing from headwaters in the Himalaya Mountains. Over the years, Bangladeshis relying on these pathogen-polluted streams for drinking water became infected with cholera and other deadly diarrheal diseases. Thousands died.
To protect the population, in the 1970s, the Bangladesh government, the United Nations Children's Fund and other organizations began encouraging a shift from surface-water sources of drinking water to ground water, through shallow wells called tube wells. Today, according to the World Health Organization, more than 90 percent of households in Bangladesh get their drinking water from 10 million private tube wells.
But that water is not safe to drink either. In the 1990s, it was discovered that the groundwater drawn from these shallow wells also is contaminated — with colorless, odorless, toxic arsenic.
“Millions of people in Bangladesh and other parts of Asia are being poisoned by drinking groundwater containing high levels of arsenic,” Michael says. “This arsenic occurs naturally, as a result of the region's hydrology and geology. The arsenic has leached from sediments into the groundwater, which is now being tapped by shallow wells.”
Drinking water contaminated with high levels of arsenic doubles the risk of cancer, causes cardiovascular disease and inhibits the mental development of children. The World Health Organization estimates that thousands of people currently die each year in southern Asia from long-term exposure to arsenic.
After earning her doctorate from the Massachusetts Institute of Technology in 2005, Michael, a native of Aliquippa, Pa., traveled to Bangladesh to study the groundwater contamination problem firsthand as a postdoctoral fellow working with the U.S. Geological Survey. She joined the UD faculty in 2008.
“Even in the rural areas of Bangladesh, the population density is very high,” Michael says. “There are pressing problems of poverty and how to feed so many people, and then you add on the water issues. Visiting the villages, the enormity of the problem really struck me,” she notes. “Yet the people are amazing and generous. They welcomed us into their homes.”
With arsenic leaching into shallow wells, a logical solution is to dig deeper wells to reach uncontaminated aquifers for safe drinking water. However, farmers also want access to this uncon-taminated water to irrigate their rice paddies. And that's a problem, according to Michael's research.
In 2008, Michael generated a model of groundwater flow in the Bengal Basin, which showed that an uncontaminated domestic well more than 500 feet (150 meters) could remain arsenic-free for at least a thousand years. However, she projected an entirely different scenario for deep irrigation wells, which use mechanized pumps instead of hand pumps to bring groundwater to the surface. The high volumes of water drawn by these irrigation systems would induce a much faster downward migration of arsenic-contaminated surface water into the deep aquifer.
Michael expanded her models and convincingly demonstrated this in a recent study with colleagues at Columbia University and Lamont-Doherty Earth Observatory, which was published in the prestigious journal Nature Geoscience.
The team injected arsenic-rich water into a deep aquifer in Bangladesh, then monitored arsenic levels over nine days. The arsenic fell by 70 percent after 24 hours and continued to decline.
Where did the arsenic go? It stuck to the surface of deep sediment particles through a process called adsorption. The more oxidized the sediments, the more arsenic the sediments took out of circulation — a finding that may help to keep wells safe not only in Bangladesh, but elsewhere around the world, including in the United States, if wells are located within these types of sediments.
When these results were applied to Michael's hydrological model of the entire Bengal Basin — the aquifer serving most of Bangladesh and the neighboring Indian state of West Bengal — the team found that the risk of arsenic contamination is limited when wells are restricted to household use, but increases significantly if they are also used for irrigation.
“We suggest that deep groundwater be used sparingly — only for domestic use,” Michael concludes. “We also suggest that monitoring for arsenic contamination should be widespread, particularly in areas that are shown to be vulnerable in the model.”
Currently, Khan is assisting Michael with a World Bank study of arsenic-contaminated water in Bangladesh. His focus is river-aquifer interactions in the Ganges River Basin.
When he returns to Bangladesh this summer, Khan will have the opportunity to visit his family for the first time in two years, including his father, who is a rice farmer; his mother, who is a housewife; and his 11 sisters (four are actual sisters, and seven are female cousins whom he refers to as “sisters,” as is the custom in Bangladesh). He also will collect data critical to the research.
“The hydrological models being developed by Dr. Michael are very important in that they will enable the testing of groundwater management ideas and help my country to address this drinking water crisis,” Khan says.
When he completes his doctorate, Khan hopes to follow in Michael's footsteps.
“I'll definitely go back and try to join a uni-versity in my country to conduct research and apply my knowledge to improve the situation,” he says.
Through the efforts of government, charitable organizations and collaborating universities, deep wells are being dug, and filters for removing arsenic are being developed in the quest to provide Bangladeshis with safe drinking water.
And Michael is optimistic that more progress will be made.
“In my classes at UD, I now routinely ask my students, ‘Where does your tapwater come from?'” she says. “It makes students really think about how people in the world get water, and it makes them realize that many don't have access to water that's safe to drink. We're working to help change that in Bangladesh.”