Adjustment of creatinine-adjusted values in urine to urinary flow rate: a study of eleven heavy metals and organic substances

The use of urinary monitoring in medical surveillance programs in industry requires development of an accurate and unbiased index of urinary concentrations of occupational toxins. To examine the effects of urinary flow (UF) rate on the standard creatinine (Cn)-adjusted value and the UF- and Cn-adjusted values according to Greenberg and Levine and to Araki et al. for 11 heavy metals and organic substances, 19 metal-foundry workers aged 34–59 years (mean 48), who had been exposed to lead, zinc, and copper for 2–17 (mean 10) years, were studied during four periods of the day under water-free, water-restrictive and water-loading conditions for 6 days. The blood lead concentrations of the 19 workers ranged from 22 to 59 (mean 38) g/dl. The results indicated that there was no significant OF effect on the UF- and Cn-adjusted values of Araki et al. for all urinary substances except mercury and coproporphyrin. On the other hand, the UF- and Cn-adjusted value of Greenberg and Levine was positively correlated with OF rate for all urinary substances, and the standard Cn-adjusted value was either positively or inversely correlated with OF rate for many urinary substances. Therefore, the UF- and Cn-adjusted value of Araki et al. is considered to be applicable to the measurement of most urinary substances under conditions of wide variation in OF rate.