Fluoride accumulation in invertebrates near an aluminium reduction plant in Wales

The fluoride pathway from an aluminium reduction plant was investigated by examining fluoride accumulation in the species of many invertebrate groups. Previous workers had examined only a few groups. All groups showed increasing accumulation from control to medium exposure to high exposure zones. In the high exposure zone, the scavengers, millipedes and woodlice, had the greatest mean accumulation of approximately 1100 μg Fg⁻¹. The predatory spiders (393 μg Fg⁻¹) and harvestmen (258 μg Fg⁻¹) were next. These were followed by slugs and snails (190 μg Fg⁻¹) feeding on decaying and fresh plant material, earthworms (184 μg Fg⁻¹) feeding on organic material in the soil, the omnivorous beetles (50 μg Fg⁻¹) and the predatory centipedes (48 μg Fg⁻¹). The herbivorous grasshoppers contained least (20 μg Fg⁻¹). The overall sequence of increasing fluoride was: herbivores—omnivores—predators—scavengers. In some groups, such as beetles, the levels were comparatively low, but the same sequence occurred. The fluoride content of each species is important in the transfer of fluorides to predators, but does not necessarily reflect the level of involvement in the fluoride pathway through the ecosystem.