[The biological monitoring of occupational exposures to solvents by using their urinary concentrations]

For many years biological monitoring of occupational exposure to solvents is achieved via their specific urinary metabolites. In the last 10 years many publications have shown that the urinary concentrations of unchanged solvents are well correlated with environmental exposure and could therefore be used for biological monitoring. For acetone, methanol, methyl ethyl ketone and methyl iso butyl ketone, the American Conference of Governmental Industrial Hygienists and the Deutsche Forschungsgemeinschaft have proposed urinary concentrations of substance itself as biological exposure indices. A critical revision of the literature on this matter reveals discrepancies between the results obtained by different authors. The correlations between environmental data and respective solvents give excellent indices of correlation. However, the differences observed when comparing the regression lines obtained from different research groups are very wide. For example, for an exposure to toluene corresponding to 50 ppm, some authors found urinary concentrations equal to 35 micrograms/l, others found urinary concentration higher than 100 micrograms/l. Similarly for benzene, styrene and methyl ethyl ketone the differences were also marked. We have not identified an explanation for such different results. Biological data variability could help to explain part of these disagreements. It should also be remembered that for benzene, the analytical methodology performed in different conditions can give rise to very different results. The mechanisms of excretion of organic solvents in urine are discussed considering biological variability and analytical method problems. The current hypotheses do not allow a satisfactory interpretation of the literature results. In conclusion further experience is needed that will more clearly show which results better express the relationship between occupational exposure to organic solvents and their specific urinary concentrations.