Fluoride content of water, dust, soils and cereals in the endemic dental fluorosis area of Khouribga (Morocco).
The fluoride contents of drinking water, dust, soil, straw, raw barley (ears and stems) and barley grains in Khouribga were compared with those from Beni-Mellal, 90 km east of Khouribga where no fluorosis occurs. Identical fluoride levels were found in water samples from both areas, whereas high amounts of F- were in soil, dust, dried straw and dried barley grown in Khouribga. Equilibrated with water, large phosphate rock particles, probably of francolite, and smaller phosphate particles of clay-contaminated francolite, randomly collected in the factories of Khouribga never contained more than 1.2 parts/10(6) F-. Unwashed samples of straw and whole barley had a higher F- content than washed samples. The marked fluorosis in herbivores of the Khouribga area comes more from the ingestion of dust-contaminated food (unwashed straw and unwashed raw barley) with a high fluoride content than from inhalation of fluoride-containing dust. By contrast, the endemic human fluorosis in the same region is mostly due to inhalation of fluoride-containing phosphate dust, and not to fluoride in the drinking water and only exceptionally to fluoride deposited during storage onto cereals, because grains grown in Khouribga have a low fluoride content.