URINARY-EXCRETION OF CHROMIUM BY HUMANS FOLLOWING INGESTION OF PICOLINATE - IMPLICATIONS FOR BIOMONITORING

This study investigated the variability in urinary chromium (Cr) excre tion following the ingestion of Cr picolinate by human volunteers. A p harmacokinetic model was used to estimate the bioavailability of Cr fr om ingested Cr picolinate using known distribution patterns and elimin ation rates of Cr by humans. The possible advantages of using sequenti al, individual spot, or 24-hr urine sample collection for biomonitorin g of Cr exposure were examined. Background concentrations of urinary C r determined from the spot samples in this study compared well with va lues reported by others. The variability in urinary excretion of Cr in untreated volunteers indicated that it is virtually impossible to dis tinguish exposures to most occupational and virtually all environmenta l exposures to Cr. Sequential urine sampling was found superior to bot h 24-hr and spot urine collection for indicating exposure to Cr picoli nate. The extent of absorption of Cr from the picolinate matrix in the gastrointestinal tract was 2.80 +/- 1.14% (SD). It was estimated that 10 mg of soil containing between 7,400 and 52,000 mg Cr(III)/kg would have to be ingested by an adult to result in urinary excretion of Cr clearly above the upper bound of Cr in urine from background populatio ns (1.8 mu g Cr/liter), depending on certain assumptions regarding bio availability. This study supports the results of other recent work tha t demonstrated urinary excretion of Cr resulting from low-level enviro nmental exposure is unlikely to be distinguished from that resulting f rom dietary uptake.