Fluoride and Kidneys
Fluoride plays perhaps more mischief with the kidneys than with any other organ.
See this excellent summary of the literature by Carol Clinch.
“One of the strongest physiological effects of fluorides in drinking water (e.g. hydrofluorosilicic acid) is in the kidney, a point to consider in light of increased rates of kidney failure during recent decades.
Kidney disease markedly increases an individual’s susceptibility to fluoride toxicity. In healthy adults, the kidneys are able to excrete approximately 50% of an ingested dose of fluoride. However, in adults with kidney disease the kidneys may excrete as little as 10 to 20% and young children may only excrete 15% of an ingested dose – thus increasing the body burden of fluoride and increasing an individual’s susceptibility to fluoride poisoning (e.g. renal osteodystrophy).