1. The excretion of fluoride is examined among aluminum smelter workers over the course of a seven-day workweek. The data for the first three days of work is best described by the first cycle of a parabolic curve. Each curve is characteristic of the level of exposure associated with specific jobs and individual smelter hygienic conditions.

2. The variability associated with the post-shift values after apparent equilibrium is attained is extreme. Such variability is probably due in large part to differences in exposure occurring during the last few hours of that work-day. This is further augmented as essentially all the absorbed fluoride is excreted as the near-equilibrium state is attained.

3. Because of this variability, the use of the post-shift urinary fluoride concentration as an indicator of exposure conditions should be limited to groups of workers, rather than individuals, at possible risk.

4. It appears that a urinary fluoride sample taken any day after the third day of the shift is an adequate post-shift fluoride exposure indicator among these groups of workers.

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*Original abstract online at https://pubmed.ncbi.nlm.nih.gov/1249651/

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