Variability in urinary mercury excretion.

This report investigates quantitatively the extent to which 24-hour urinary mercury excretion can be predicted from the concentration of mercury in spot samples. The correlation between these quantities can be significantly improved by the application of a correction for urinary dilution and by restricting spot samples to the day's first excretion. If these precautions are taken, we find that for 68% of the samples the 24-hour excretion, Q, is in the range of 0.75 C' less than Q less than 1.31 C', where C' is the mercury concentration of a day's first excretion. The width of this range appears to be primarily determined by variations in a person's daily urinary volume and by the frequent occurrence of diurnal cycles.