Personal air sampling and biological monitoring of occupational exposure to the soil fumigant cis-1,3-dichloropropene

Biomonitoring as a tool in the human health risk characterization of dermal exposure

Dermal exposure is an important factor in risk characterization. In occupational settings it becomes relatively more important because of the continuous reduction in inhalation exposure. In the public health arena, dermal exposure may also form a significant contribution to the total exposure. Dermal exposure, however, is difficult to assess directly because it is determined by a host of factors, which are difficult to quantify. As a consequence, dermal exposure is often estimated by application of models for external exposure. In combination with modeled or measured data for percutaneous penetration, these provide an estimate for the internal exposure that is directly related to the systemic effects. The advantages and drawbacks of EASE (Estimation and Assessment of Substance Exposure) and RISKOFDERM (Risk Assessment of Occupational Dermal Exposure), two models for external exposure that are mentioned in the Technical Guidance Document for the European Union risk assessments performed under the Existing Substances Regulation (EEC/793/93), are discussed. Although new chemicals regulation (REACh, 1907/2006/EC) is now in place in the European Union, the principles applied under the previous legislation do not change and the same models will continue to be used. The results obtained with these models for styrene, 2-butoxyethanol, and 1-methoxy-2-propanol in specific exposure scenarios are compared with an alternative method that uses biomonitoring data to assess dermal exposure. Actual external exposure measurements combined with measured or modeled percutaneous penetration data give acceptable results in risk assessment of dermal exposure, but modeled data of external dermal exposure should only be used if no other data are available. However, if available, biomonitoring should be considered the method of choice to assess (dermal) exposure.

Mercapturic acids revisited as biomarkers of exposure to reactive chemicals in occupational toxicology: a minireview

A minireview is presented concerning the use of mercapturic acids as biological exposure index for electrophilic chemicals. Besides pure analytical aspects, this minireview considers possible issues in relation to (a) the added value of mercapturic acids as compared to other well validated biomarkers of exposure and (b) the high inter-individual variability in mercapturic acids excretion. Recent field and/or experimental studies confirm the usefulness of mercapturic acids as biological exposure index for electrophilic chemicals and suggest the interest of a toxicogenetic approach for a better interpretation of the results of biological monitoring.

Benzylmercapturic acid is superior to hippuric acid and o-cresol as a urinary marker of occupational exposure to toluene

The present study was initiated to examine whether urinary benzylmercapturic acid (or N-acetyl-S-benzyl cysteine, BMA), a mercapturate metabolite of toluene, increases in relation to the intensity of toluene exposure, and whether this metabolite is a better marker of occupational exposure to toluene than two traditional markers, hippuric acid and o-cresol. Accordingly, end-of-shift urine samples were collected from 122 printers and 30 office clerks (all men) in the second half of a working week. Solvent (toluene) exposure of the day (8 h) was monitored by means of diffusive sampling. Quantitative relation with toluene showed that BMA had a greater correlation coefficient with toluene (r = 0.7) than hippuric acid (r = 0.6) or o-cresol (r = 0.6). The levels in the urine of the non-exposed control subjects were below the detection limit of 0.2 microg/l for BMA, whereas it was at substantial levels for hippuric acid and o-cresol (239 mg/l and 32 microg/l as a geometric mean, respectively). Thus, BMA, hippuric acid and o-cresol could separate the exposed from the non-exposed when toluene was at < 1, 50 and 3 ppm, respectively. Overall, therefore, it appeared reasonable to conclude that BMA is superior to hippuric acid and o-cresol as a marker of occupational exposure to toluene.

Mercapturic acids in the biological monitoring of occupational exposure to chemicals

This paper reviews several procedures for determination of mercapturic acids in urine. Special attention was paid to methods useful in relation to human exposure to industrial pollutants, without any description for less sensitive methods used in animal research. Gas chromatographic and liquid chromatographic procedures were considered together with the little information available about thin layer chromatography and immunochemical techniques. After a description of the main industrial pollutants which lead to synthesis of their specific mercapturic acids, the methods for analysing these products are synthetically reported. The comparison among difficulties in sample preparation, complexity of instrumentation and their cost/benefit ratio are discussed.

Occupational exposure to cis-1,3-dichloropropene: biological effect monitoring of kidney and liver function

OBJECTIVES

To investigate the possible effects of occupational exposure to the nematocide cis-1,3-dichloropropene (cis-DCP) on function of the kidney and liver in the starch potato growing region in The Netherlands.

METHODS

The study involved 13 commercial application workers exposed to cis-DCP for 117 days, and 22 matched control workers. The inhalatory exposure of the application workers was estimated from biological monitoring data. All workers collected urine and serum samples before, during, and after the fumigation season for monitoring of variables for kidney and liver function. Renal effect variables were alanine aminopeptidase (AAP), N-acetyl-beta-D-glucosaminidase (NAG), retinol binding protein (RBP), and albumin (ALB) in urine, and beta(2)-microglobulin (beta(2)M-S) and creatinine in serum (Creat-S). Liver variables were alanine aminotransferase (ALAT), aspartate aminotransferase (ASAT), gamma-glutamyltranspeptidase (GGT), alkaline phosphatase (ALP), and total bilirubin (TBIL) in serum and the urinary ratio of 6-beta-hydroxycortisol to free cortisol (betaOHC/COR).

RESULTS

The geometric mean exposure of the application workers was 2.7 mg/m(3) (8 hour time weighted average (8 hour TWA)); range 0.1-9.5 mg/m(3). No differences were found between the values of the renal effect variables or the liver variables of the exposed group and the control group, except a lower urinary ratio of betaOHC/COR in the exposed group. This was not considered to be related to the exposure to cis-DCP. No dose-effect relations were found between the exposure indices and the effect variables.

CONCLUSIONS

The present study does not provide evidence that occupational exposure to cis-DCP in the starch potato growing region causes adverse effects on the kidney or liver at 8 hour TWA exposure concentrations below 9.5 mg/m(3) (2 ppm).

Dermal absorption of cis-1,3-dichloropropene vapour: human experimental exposure

1. The relevance of skin absorption of cis-1,3-dichloropropene (cis-1,3-DCP) vapour as a route of entry compared to inhalatory uptake has been assessed in human volunteers under controlled exposure conditions. 2. Five adults (four males and one female) were dermally exposed on the forearm and hand during 45 min to 86 mg/m3 cis-1,3-DCP. 3. Dermal uptake was assessed by determination of the main cis-1,3-DCP metabolite in urine: the mercapturic acid conjugate of cis-1,3-DCP (cis-1,3-DCP-MA). 4. When whole-body dermal exposure to vapour is compared to inhalatory exposure, the uptake through the skin is estimated to be about 2-5% of the inhalatory absorption.