Contribution of trona (magadi) into excessive fluorosis—a case study in Maji ya Chai ward, northern Tanzania

Excessive fluoride ingestion predominantly comes from drinking water sources. However, prevalence and severity of dental and skeletal fluorosis in northern Tanzania have been reported to be higher than would be expected from ingestion of fluoride through drinking water alone. This study aimed at investigating the contribution of “trona” (also locally known as magadi) a food additive, to the prevalence and severity of fluorosis in northern Tanzania. The study was carried out in four villages (Embaseni, Kitefu and Ngurdoto) in Maji ya Chai ward; and Nkoanekoli in Poli ward, in Arusha region, Tanzania. Analysis of fluoride concentrations was carried out in drinking water sources as well as in magadi samples. Assessment of the prevalence of dental fluorosis using Dean's Index Method was carried out for a population of 2217 pupils in four primary schools located in the case study area. Fluoride concentration in drinking water sources was found to range from 1.7 to 11.3 mg/l, while the concentration in magadi samples in case study villages were in the range of 0.21 to 0.9 mg/g. Total fluoride ingestion through magadi and water were established to be 11.74 mg/person/day in Embaseni, 36.1 mg/person/day in Ngurdoto, 10.88 mg/person/day in Kitefu and 5.7 mg/person/day in Nkoanekoli villages. Levels of total fluoride ingestion were directly correlated with Community Fluorosis Index (CFI) values, which were found to be 3.32 (in Embaseni), 3.67 (in Ngurdoto), 2.2 (in Kitefu) and 1.47 (in Nkoanekoli). The village with the highest fluoride consumption rate showed the highest CFI as well. High levels of fluoride concentrations in magadi suggest that excessive fluorosis in northern Tanzania may be due to the use of magadi in food preparations.