Comment by ZYbCRq22HbJ2y7

> The fractional retention or balance of fluoride at any age depends on the quantitative features of absorption and excretion. For healthy, young, or middle-aged adults, approximately 50 percent of absorbed fluoride is retained by uptake in calcified tissues, and 50 percent is excreted in the urine. For young children, as much as 80 percent can be retained owing to increased uptake by the developing skeleton and teeth (Ekstrand et al., 1994a, b). Such data are not available for persons in the later years of life, but based on bone mineral dynamics, it is likely that the fraction excreted is greater than the fraction retained.

https://www.ncbi.nlm.nih.gov/books/NBK109832/=

> .9 Radiographic detection of teeth and skeletal changes and microscopic examination of affected bone are helpful adjunct procedures for diagnosis.

> Histopathologic and radiographic examination of bones detects bone lesions and tentatively confirms osteofluorosis.14,26 Biopsy or rib or coccygeal vertebrae is used to obtain samples for skeletal fluoride analysis.23

https://www.sciencedirect.com/science/article/abs/pii/B03230...

https://en.wikipedia.org/wiki/Skeletal_fluorosis

> We have developed a localized noninvasive nuclear magnetic resonance (NMR) method for determining the accumulated bone fluoride content in human index fingers

https://pubmed.ncbi.nlm.nih.gov/2339643/

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It sounds like people who have time to pay attention to this have a better chance of discerning a methodology of assay.