Monitoring of occupational exposure to dichloromethane by diffuse vapor sampling and urinalysis

Biological monitoring of occupational exposure to dichloromethane by means of urinalysis for un-metabolized dichloromethane

The objective of the study is to establish exposure-excretion relationship between dichlorometane (DCM) in air (DCM-A) and in urine (DCM-U) in workplace to confirm a previous report. Male workers in a screen-printing plant participated in the study. Time-weighted average DCM-A was measured by diffusive sampling followed by gas-chromatography (GC), and DCM in end-of-shift urine samples was by head-space GC. The data were subjected to regression and other statistical analyses. In practice, 30 sets of DCM-A and DCM-U values were available. The geometric mean DCM-A was 8.4 ppm and that of DCM-U (as observed) was 41.1 µg/l. The correlation coefficients (0.70-0.85) were statistically significant across the correction for urine density. Thus, the analysis for un-metabolized DCM in end-of-shift urine samples is applicable for biological monitoring of occupational exposure to DCM, in support of and in agreement with the previous report. In conclusion, biological monitoring of occupational DCM exposure is possible by use of analysis for un-metabolized DCM in end-of-shift urine.

Simplified procedures for estimation of biological occupational exposure limits

OBJECTIVES

To simplify the procedures to estimate biological occupational exposure limits (BOELs) by use of the ratio of geometric mean (GM) concentration of un-metabolized organic solvent in urine (U-GM) over GM organic solvent concentration in air (A-GM) (the [U-GM/A-GM] ratio).

METHODS

Occupational Exposure Limits (OELs) and BOELs were cited from publications from the Japan Society of Occupational Health (JSOH) and the American Conference of Governmental Industrial Hygienists (ACGIH). Data on [U-GM/A-GM] and the SLOPE of exposure-excretion regression line were collected from published articles (men and women were treated separately). Correlation analysis and paired t test were employed as the method to examine statistical significances.

RESULTS

Significant linear correlation was established between the SLOPE and the [U-GM/A-GM]. Thus, it was considered to be possible to calculate the SLOPE value from the [U-GM/A-GM]. Previously established equation of BOEL = SLOPE × OEL allowed to estimate BOEL values in 22 cases of data sets. The comparison of the estimated BOELs with the existing BOELs (JSOH's BOELs and ACGIH's BEIs) in terms of the ratio of [(estimated BOEL)/(existing BOEL)] showed that the ratios for the 22 cases probably distributed log-normally with a GM of 0.85, and the maximum was 5. Therefore, the estimated BOEL may be generally applicable in occupational health when BOEL remains yet to be established. In the worst case, the estimated BOEL may be five times greater than it should be. The recommended procedures for application of estimated BOEL values were described.

CONCLUSION

Simplified procedures for estimation of BOEL values are proposed.

Estimation of biological occupational exposure limit values for selected organic solvents from logartihm of octarol water partition coefficient

OBJECTIVES

For several organic solvents (solvents in short), biological occupational exposure limits (BOELs) have been established for un-metabolized solvents in urine, based on the solvent exposure-urinary excretion relationship. This study was initiated to investigate the possibiliy of estimating a BOEL from the Pow (the partition coefficient between n-octyl alcohol and water), a physico-chemical parameter.

METHODS

Data were available in the literatures for exposure-excretion relationship with regard to 10 solvents for men and 7 solvents for women.

RESULTS

Statistical analysis revealed that the slopes (after correction for molecular weights and logarithmic conversion) of the exposure-excretion regression lines linearly correlated (p<0.01) with the log Pow values the respective solvents. No significant difference (p>0.05) was observed between men and women, and it was acceptable to combine the data for the two sexes. Thus the log Pow-log slope relation was represented by a single equation for both sexes. Based on the observations, procedures were established to estimate BOEL values from Pow. Successful estimations of BOELs for styrene, tetrahydrofuran and m-xylene (a representative of xylene isomers) were calculated as examples.

CONCLUSIONS

The present study proposed promising procedures for estimation of a BOEL from the Pow.

Validation of urine density correction in cases of hippuric acid and un-metabolized toluene in urine of workers exposed to toluene

To investigate if it is appropriate to apply urine density correction when a urine sample is dense or dilute. Data on hippuric acid (HA-U), toluene (Tol-U), creatinine (CR) and specific gravity (SG) in end-of-shift urine samples and exposure to air-borne toluene were cited from previous publications. In practice, 837 cases were available, and they were classified into dense, intermediate and dilute groups taking 0.3 and 3.0 g/l of CR and 1.010 and 1.030 of SG as cut-off points. Lines of regression of HA-U and Tol-U (as observed, CR-corrected or SG-corrected) with air-borne toluene were calculated for each density groups, and correlation coefficients (CCs) were compared. The dense groups gave CCs similar to those of the intermediate groups. Dilute versus intermediate group comparison also gave promising results. These conclusions were however based primarily on the findings with observed values, because the numbers of cases in the dilute or dense group were limited when CR- or SG-correction was applied. Literature survey showed that urine density correction does not always improve the correlation between solvents in air and exposure makers in urine. It was concluded that no correction for urine density may be necessary in evaluating HA-U and Tol-U in dense (and probably also dilute) urine samples as markers of occupational toluene exposure. Just in case when correction for urine density is desired for any reason, SG-correction may be recommended.

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.

Biological monitoring of workers exposed to dichloromethane, using head-space gas chromatography

A biological monitoring method for urinary dichloromethane (DCM) has been developed by using head-space gas chromatography with FID detection. The calibration curve is linear in a wide range of DCM levels between 0.01 and 2 mg/l. The recovery rate is almost 100% and within-run coefficients of variation are 2.9-3.7%. A highly significant correlation is found between exposure levels and urinary concentrations of DCM. Determination of urine DCM by this method has many advantages such as sample storage, no need for correction of urine concentration, absence of gender difference and also no confounding effect of glutathione S-transferase T1 polymorphism.

Headspace solid-phase microextraction for the determination of benzene, toluene, ethylbenzene and xylenes in urine

A method for the determination of benzene, toluene, ethylbenzene and xylenes (BTEX) in urine of people exposed to these airborne pollutants present in the living environment, has been described. Solid-phase microextraction has been used for sampling BTEX from the headspace of urine and gas chromatography-mass spectrometry has been applied for the selective analysis of chemicals. The method has the following features: small volume of urine (2 ml) needed, linearity in the range of interest (from the limit of detection up to 5000 ng/l) with coefficient of correlation > or =0.998, limit of detection in the range 12-34 ng/l, good repeatability (coefficient of variation 2-7%), high specificity. The stability of the urine sample during storage (-20 degrees C) was evaluated: BTEX remained stable for up to 2 months. The assay has been successfully applied to the biological monitoring of two subjects environmentally exposed to airborne BTEX in an urban area.