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News Release

April 22, 2009


Mark Shwartz, Woods Institute for the Environment: (650) 723-9296,

Stanford researchers seek low-cost solutions to Africa's sanitation crisis

Each year, diarrhea kills an estimated 1.8 million people worldwide. More than 90 percent of the victims are children younger than 5 in developing countries. What makes the problem especially tragic is that it seems so preventable.

Diarrhea usually results from drinking water contaminated with human feces, coming in contact with a person with poor personal hygiene or exposure to a contaminated surface. About 1 billion people lack access to adequate freshwater supplies, and approximately 2.8 billion do not have access to basic sanitation, so the problem is particularly daunting.

Enter Jenna Davis and Alexandria Boehm of Stanford University. In 2006, Davis, an authority on sanitation in the developing world, and Boehm, an expert on microbial contamination in freshwater and coastal environments, were awarded a two-year Environmental Venture Projects grant from Stanford's Woods Institute for the Environment to find solutions to the problem of diarrhea-related deaths among children in Africa.

The focus of the study is Dar es Salaam, the largest city in Tanzania. Historically, residents of the peri-urban communities surrounding Dar have relied on water from surface sources or shallow wells that are in close proximity to household pit latrines. "That means when people defecate, the waste stays under the house," said Davis, an assistant professor of civil and environmental engineering and a fellow at the Woods Institute. "As a result, those shallow wells are very vulnerable to microbial contamination."

To address the situation, city water and sanitation officials have drilled a series of bore wells that tap into clean aquifers deep below the surface. High-quality water is then pumped into storage tanks connected to sets of four to six taps. "Most of the water from the bore wells meets the World Health Organization guidelines for E. coli bacteria in drinking water," said Boehm, an assistant professor of civil and environmental engineering. "Concentrations are typically less than 1 bacterium per 100 milliliters water."

For a little money, residents can go to the taps and carry clean water back to their homes. Many people use the bore-well water for cooking and drinking. But so far, there has been little improvement in their overall health. City water officials want to know why and have turned to the Stanford team for answers.

Household surveys

In the summer of 2008, Davis, Boehm and a team of Stanford students and postgraduates traveled to Dar to study 300 households over a 10-week period. The research team hired Tanzanian enumerators to conduct surveys and interact directly with the households. The enumerators visited each household four times. On the first visit, they collected behavioral information, primarily from female heads of households ("the mothers"), and tested stored water and the hands of family members for indicators of fecal contamination.

Approximately 7,000 water and hand samples were collected during the study. Laboratory analysis revealed very high levels of bacterial contamination on the hands and in the stored drinking water of study participants, even though the deep bore-well water collected at the source was generally of good quality.

"There appears to be something in the transport and storage that is contaminating the water," Davis explained. "It's probably happening when people use their fecal-contaminated hands to scoop water out of their home containers. Another possibility is that the stored water containers used for fetching water are not cleaned regularly."

A major challenge facing many households is distance. Some homes are 200 yards from the clean tap water, and a typical water container weighs 44 pounds when full. "We know that when people haul water from a distance, the first thing they do is drink it, then they cook, and then they wash their kids, themselves and sometimes their animals," Davis said. "So they may not have enough water for adequate personal hygiene."

For the second round of visits, the researchers separated the households into four groups. Each group was given generic information about how germs are spread through the five F's—feces, flies, field, food and fingers. "We used pictures showing several ways to prevent the spread of germs, such as boiling or chlorinating the water," Davis explained. "One of the four groups received only the generic information. A second cohort got the generic information plus the results of their water test. The third cohort got the generic information and their hand test results. The fourth group got everything—generic information, the water test results and the hand test results. The idea builds on basic health behavior-change theory: The more tailored and less generic the message is, the more effective it should be at motivating change."

'More is not better'

The preliminary results were surprising. Groups that received hand data or water data alone seemed to have a more positive response than households that got both hand and water test results. "It turns out that more is not better," Davis said. "Even though we spent an equal amount of time discussing water-related strategies and hand hygiene-related strategies, there was a bigger behavioral change on the hand hygiene side than on the water side."

The researchers are in the process of finalizing the survey data from their Environmental Venture Project. Meanwhile, in September 2008, Davis and her colleagues were awarded a three-year National Science Foundation grant to expand the number of households and the length of the study. "We're aiming for a full year, which would allow us to monitor behaviors in both the dry and wet seasons," she said. Data collection will begin in mid-2009, and the results could lead to low-cost solutions that reduce the incidence of diarrhea for tens of millions of children in sub-Saharan Africa and throughout the developing world.

Other members of the Stanford research team are Gary Schoolnik, professor of medicine and of microbiology and immunology; Abby King, professor of health research and policy and of medicine; and Cynthia Castro, research associate at the Stanford Prevention Research Center.

Mark Shwartz is communications manager at the Woods Institute for the Environment at Stanford.



Jenna Davis, Woods Institute for the Environment and Department of Civil and Environmental Engineering: (650) 725-9170,

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