Biological Monitoring of Workers Exposed to Carbon Tetrachloride Vapor

Excretion of unchanged volatile organic compounds (toluene, ethylbenzene, xylene and mesitylene) in urine as result of experimental human volunteer exposure

OBJECTIVES

To investigate elimination of unchanged volatile organic compounds (VOC's) through urine and the use of respective data for occupational exposure assessment, six volunteers were exposed under controlled conditions to toluene (TOL), ethylbenzene (EB), xylene (XYL) and mesitylene (MES) at concentrations ranging from 20 to 200 mg/m(3). The study was to elicit the toxicokinetic data and compare the precision of VOC's exposure assessment based on determining unchanged compounds in blood, urine and their metabolites in urine.

METHODS

During and after exposure blood and urine samples were analysed by gas chromatography using the headspace and SPME headspace technique

RESULTS

The kinetics of VOC's elimination in urine complied with an open two-compartment model. The (half-time) T (1/2 )values varied from 0.45 to 0.88 h for phase I and from 6.7 to 19.2 h for phase II. The precision of the method for unchanged VOC's was similar to that based on unchanged compounds in blood and better than their main metabolites in urine.

CONCLUSION

The obtained result indicate that determining unchanged VOC's in urine can be used as an exposure test even in the ranges of VOC's in the air that are much lower than the current TWA for occupational exposure.

Biological monitoring of exposure: trends and key developments

The concept of biological monitoring (BM) has gained the special interest of individual scientists and international organizations. Today, when analytical problems have almost ceased due to new laboratory techniques and quality assurance systems, the methods for interpretation of results have become the most important issue. There are important discrepancies regarding the role of biological monitoring of occupational exposure between Europe and the United States. BM has been an important tool of medical health surveillance in the European countries. In the United States it belongs rather to the field of occupational hygiene. It seems that both the approaches can be accepted. More attention should be paid to the development of the truly health-based biomarkers of exposure based on the dose-effect and dose-response relationships. New areas of application of BM of occupational exposure include determination of DNA and protein adducts, unchanged volatile organic compounds in urine, monitoring of exposure to pesticides, antineoplastic drugs, hard metals, and polycyclic aromatic hydrocarbons. In the general environment BM is the most valuable tool for acquiring knowledge of current levels of internal exposure to xenobiotics, identifying the hot spots and developments in trends of exposure. BM can provide policy makers with more accurate information on the control measures undertaken. At present, the main areas include heavy metals, persistent organic pollutants and pesticides. BM of chemical exposure has become increasingly important in the assessment of the health risk in occupational and environmental medicine. Therefore it would be worthwhile to include BM in the curricula for the training of occupational hygienists.

Gases and organic solvents in urine as biomarkers of occupational exposure: a review

A brief review of urine analysis in studies of occupational exposure to volatile organic compounds and gases is provided. Analysis of exhaled breath for volatile compounds does not have a long history in occupational medicine. A number of studies has been undertaken since the 1980s, and the methods are well enough accepted to be put forward as biological equivalents of threshold limit values (TLVs) for some volatile organic compounds (VOCs) such as acetone; methanol; methyl ethyl ketone (MEK); methyl isobutyl ketone (MIBK); tetrahydrofurane; dichloromethane. In the last 20 years many scientific articles have shown that the urinary concentrations of unchanged solvents are correlated with environmental exposure and could be used for biological monitoring. The use of urine analysis of unchanged solvents in occupational applications is not yet widespread. Nonetheless, in the short time since its application, a number of important discoveries has been made, and the future appears bright for this branch of analysis. In this paper, the basic concepts and methodology of urine analysis are briefly presented with a critical revision of the literature on this matter. The excretion mechanisms of organic solvents in urine are discussed, with regard to biological variability, and the future directions of research are described.

The urinary excretion of solvents and gases for the biological monitoring of occupational exposure: a review

'In the field' application of the measurement of urinary excretion of unmodified solvent for the biological monitoring of exposed workers has been investigated in many recent papers. The results obtained for several solvents are reviewed. The values of correlation coefficients (r) and regression lines obtained for benzene, toluene, xylene, styrene, n-hexane, cyclohexane, 2- and 3-methylpentane, methyl chloride, tetrachloroethylene, carbon tetrachloride, methyl chloroform, p-dichlorobenzene, nitrous oxide, halothane, isoflurane, enflurane, acetone, methyl ethyl ketone and methyl isobutyl ketone are presented. The correlations observed were generally good: r values range from 0.50-0.97, and the majority are between 0.84 and 0.90. The regression lines reported for the same solvent in different studies present some variability: this is possibly due to an inadequate control of factors influencing the relationship between external dose and absorption, such as differences in body burden, work load, individual characteristics, etc. These factors are discussed. As a whole, results reported in the literature show that measuring of urinary excretion of unmodified solvents provides a highly sensitive and specific exposure index, and can also be applied for the biological monitoring of occupational exposure to low levels of solvents or to solvent mixtures. Nevertheless, for an adequate assessment of biological limit values, further studies evaluating the reproducibility of regression lines are needed, given that the aspects influencing the correlation between external dose and urinary excretion are fully controlled. Another crucial aspect is the correlation with early effects: even though this has yet to be evaluated for several solvents, for others such as styrene and perchloroethylene a good correlation was obtained, further supporting the usefulness of the measurement of urinary excretion of solvent for the biological monitoring of occupational exposure.