'Alzheimer' gives a simple explanation for Alzheimer's Disease. Acid air pollution by oxides of sulphur and nitrogen allows silicon hexafluoride, carrier for calcium phosphate, to be synthesised in nasal passages. It enters the brain along the olfactory nerves and decomposes, producing silicate plaques and fluoride. In the absence of skeletal material, fluoride kills neurons, causes protein tangles and impairs brain function. Administration of fluorine-containing anaesthetics, typically for hip replacement, affords temporary relief from dementia when it's excreted as aluminium hexafluoride and the same chemistry clears fluoride from the brain, suggesting ways to prevent and treat the condition.