Solvents in urine as exposure markers

Possible pitfalls and solutions are reviewed in the development and application of the methods of urinalysis for organic solvent as a biological exposure marker. In case head-space gas chromatography (HS-GC) is applied for analysis, loss of the solvent in the urine sample should be below 5% if the transfer of the sample into a HS GC vial is terminated in 5 min. When urine samples are stored in a bottle, organic solvent may partly move into the air phase in the bottle, but such loss from the water phase can be compensated by calculation, when the volumes of the air and water phases are available. Solvents in urine generally show closer correlation with the exposure intensity than the corresponding metabolite(s). When the lowest vapor exposure concentration was determined as the concentration at which the exposed subjects can be statistically separated from the non-exposed, solvent in urine can separate at a lower exposure concentration than its metabolite(s). Compared with the solvent in blood, however, solvent in urine correlates less closer to the solvent vapor exposure, especially when the vapor concentration is low, e.g. < 10 ppm toluene.