EXPERIMENTAL FLUORIDE ACCUMULATION AND TOXICITY IN THE SHORT-TAILED FIELD VOLE (MICROTUS-AGRESTIS)

Vegetation established naturally on three industrial sites contaminated by either airborne or soilborne fluorides was used to formulate dietary feed for a laboratory-reared population of field voles (Microtus agrestis L.), an herbivorous species indigenous to ail three locations. Animals exposed to laboratory diets containing 100-300 mg F kg(-1) derived from vegetation from around the aluminium smelter and fluorochemical works showed reduced live weight gain, between 40 and 100% mortality and developed marked dental lesions. These comprised banding of the enamel, loss of colour and erosion of the cutting surfaces of the incisors, and dentine cavitation and erosion of the grinding faces of the molar teeth. These morphological changes were accompanied by excessive accumulation of fluoride in the teeth. Voles consuming a diet of vegetation from the mine tailings site with a similar level of fluoride (100 mg kg(-1)) as for the other industrial locations, showed only slight dental changes and no weight loss or early mortality. This pattern for laboratory-bred voles is similar to that experienced in populations of this species in the wild, and the contrast in the severity of the dental lesions is ascribed to intersite differences in the chemical speciation and bioavailability of fluoride.