When fluorides are ingested by humans or laboratory animals, they are absorbed in the stomach and/or the intestine. Fluoride from soluble fluorides is almost completely absorbed (either as HF or F-, depending on stomach acidity). However, when fluoride is bound to aluminium, calcium etc., its release and subsequent absorption may be reduced because this combination is less soluble. When fluorides in gaseous or particulate form are breathed in, the respiratory tract, they are partially or completely absorbed depending on how soluble they are or on how big the fluoride-containing particles are.
Fluoride is then rapidly distributed in tissues. In humans and laboratory animals, fluorides mostly build up in bones and teeth, which retain about 99% of the total fluoride body burden.
Fluoride is eliminated from the body primarily through the urine. Infants retain 80 to 90% of fluoride ingested, while adults retain approximately 60%.
However, the balance of fluoride in the body (i.e. the difference between the amount of fluoride ingested and the amount excreted) can be positive or negative. This physiological balance is determined by earlier fluoride exposure, the degree of accumulation in bone, the rate at which it is released from bone and the efficiency of the kidneys in excreting fluoride. When fluoride intakes are low excretion through urine can exceed intake.
Connect With Us