At least 16 million Ethiopians are affected by excessive fluoride in their water, Al Jazeera reported in July 2019 from Mojo, a Rift Valley town trying to remove it with filters made from bones.
Lakes Ziway, Langano, Abijata and Shala on the floor of Ethiopia’s Central Rift Valley, from Sentinel-2 satellite data of April 2020 (Yonas Kidane, Wikimedia Commons, CC BY-SA 2.0) [file photo]
In small amounts fluoride strengthens teeth, which is why many countries add it to water and toothpaste. In large amounts it is toxic. It stains and mottles teeth, a condition called dental fluorosis, and in severe cases it damages bones and joints.
In Ethiopia the problem is natural. A 2015 study in the journal Fluoride estimated that about 8 million people in the Central Rift Valley are exposed to high levels of naturally occurring fluoride through drinking water, drinks and food. The World Health Organization’s guideline limit for fluoride in drinking water is 1.5 milligrams per liter.
One local answer is bone char. Cow bones collected from butchers are charred, crushed, sieved, washed and dried into a granular filter that binds fluoride as water passes through. The factory that makes the material is in Mojo, about 15 kilometers north of Adama, and was set up with project funds from Eawag, the Swiss Federal Institute of Aquatic Science and Technology.
The Oromo Self-Help Organization (OSHO) first handed out bone-char filters to 200 households, but most rejected them because they depended on outside help to test whether the filters still worked. OSHO switched to community filters, and by 2015 seven community bone-char schemes were serving more than 3,000 households, according to the study.
Researchers from Eawag and Addis Ababa University have also tested filters that mix bone char with calcium-phosphate pellets, a method known as the Nakuru technique after the Kenyan Catholic diocese that developed it, to make the filter material last longer.
Cost remains the hurdle. Eawag researchers concluded that the technology works, but the filter material must be replaced regularly, and users have limited ability and willingness to pay for fluoride-safe water.
Sources: Al Jazeera, Fluoride (journal), Eawag, Eawag CIRUS presentation