'Hidden hot springs' as a source of groundwater fluoride and severe dental fluorosis in Malawi

Addison, Marc J. and Rivett, Michael O. and Phiri, Owen L. and Milne, Nigel and Milne, Vicky and McMahon, Alex D and Macpherson, Lorna MD and Bagg, Jeremy and Conway, David I and Phiri, Peaches and Mbalame, Emma and Manda, Innocent and Kalin, Robert M. (2021) 'Hidden hot springs' as a source of groundwater fluoride and severe dental fluorosis in Malawi. Water, 13 (8). 1106. ISSN 2073-4441 (https://doi.org/10.3390/w13081106)

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Hidden hot springs likely impact rural water supplies in Malawi's Rift Valley with excess dissolved fluoride leading to localised endemic severe dental fluorosis. Predicting their occurrence is a challenge; Malawi's groundwater data archive is sporadic and incomplete which prevents the application of standard modelling techniques. A creative alternative method to predict hidden hot spring locations was developed using a synthesis of proxy indicators (geological, geochemical, dental) and is shown to be at least 75% effective. An exciting collaboration between geoscientists and dentists allowed corroboration of severe dental fluorosis with hydrogeological vulnerability. Thirteen hidden hot springs were identified based on synthesised proxy indicators. A vulnerability prediction map for the region was developed and is the first of its kind in Malawi. It allows improved groundwater fluoride prediction in Malawi's rift basin which hosts the majority of hot springs. Moreover, it allows dentists to recognise geological control over community oral health. Collaborative efforts have proven mutually beneficial, allowing both disciplines to conduct targeted research to improve community wellbeing and health and inform policy development in their respective areas. This work contributes globally in developing nations where incomplete groundwater data and vulnerability to groundwater contamination from hydrothermal fluoride exist in tandem.