[Assessment of occupational exposure of welders based on determination of fumes and their components produced during stainless steel welding]

BACKGROUND

Occupational exposure to welding fumes is a known health hazard. The aim of this study was to determine concentrations of welding fumes components such as: iron, manganese, nickel and chromium (including chromium speciation) to assess exposure of stainless steel welders.

MATERIALS AND METHODS

The survey covered 14 workers of two metallurgic plants engaged in welding stainless steel (18% Cr and 8% Ni) by different techniques: manual metal arc (MMA), metal inert gas (MIG) and tungsten inert gas (TIG). Personal air samples were collected in the welders' breathing zone over a period of about 6-7 h (dust was collected on a membrane and glass filter) to determine time weighted average (TWA) concentration of welding fumes and its components. The concentrations of welding fumes (total particulate) were determined with use of the gravimetric method. Concentrations and welding fume components, such as: iron, manganese, nickel and chromium were determined by ICP-MS technique. The total hexavalent chromium was analyzed by applying the spectrophotometry method according to NIOSH. The water-soluble chromium species were analyzed by HPLC-ICP-MS.

RESULTS

Time weighted average concentrations of the welding fumes and its components at the worker's breathing zone were (mg/m3): dust, 0.14-10.7; iron, 0.004-2.9; manganese, 0.001-1.12; nickel, < 0.001-0.2; and chromium <0.002-0.85 (mainly Cr(III) and insoluble Cr(VI)). The maximum admissible limits for workplace pollutants (TLV-TWA) were exceeded for manganese and for insoluble chromium Cr (VI). For Cr (III) the limit was exceeded in individual cases.

CONCLUSIONS

The assessment of the workers' occupational exposure, based on the determined time weighted average (TWA) of fumes and their components, shows that the stainless steel welders worked in conditions harmful to their health owing to the significantly exceeded maximum admissible limits for manganese and the exceeded TLV value for insoluble chromium (VI).

[Selenium determination in plasma/serum by inductively coupled plasma mass spectrometry (ICP-MS): comparison with graphite furnace atomic absorption spectrometry (GF-AAS)]

BACKGROUND

The present study was aimed at comparing two techniques of selenium (Se) determination in serum/plasma samples: inductively coupled plasma mass spectrometry (ICP-MS) and graphite furnace atomic absorption (GF-AAS).

MATERIALS AND METHODS

Blood samples were collected by venipuncture, using Venosafe closed blood sampling system. The samples were centrifuged. The measurements were performed by Elan DRC-e mass spectrometry, Perkin Elmer, SCIEX, USA and Unicam Solar 989 QZ atomic absorption spectrometry. Reference material, Clincheck Serum Control Level 1 (Recipe, Germany), was used to verify the determinations. The Laboratory participates in external quality control (G-EQUAS).

RESULTS

Analytical parameters for both techniques are respectively: ICP-MS--precision 5.9%, limit of detection 0.19 microg/l, repeatability 5.5%, trueness 2.4%, bias 97.6%, GF-AAS--precision 8%, limit of detection 3.4 microg/l, repeatability 7.2%, trueness 6.8%, bias 93.2%.

CONCLUSIONS

The benefits of the ICP-MS technique are high accuracy, low detection limits and the possibility of multi-element analysis.

The effects of low environmental cadmium exposure on bone density

Recent epidemiological data indicate that low environmental exposure to cadmium, as shown by cadmium body burden (Cd-U), is associated with renal dysfunction as well as an increased risk of cadmium-induced bone disorders. The present study was designed to assess the effects of low environmental cadmium exposure, at the level sufficient to induce kidney damage, on bone metabolism and mineral density (BMD). The project was conducted in the area contaminated with cadmium, nearby a zinc smelter located in the region of Poland where heavy industry prevails. The study population comprised 170 women (mean age=39.7; 18-70 years) and 100 men (mean age=31.9; 18-76 years). Urinary and blood cadmium and the markers of renal tubular dysfunction (beta(2)M-U RBP, NAG), glomerular dysfunction (Alb-U and beta(2)M-S) and bone metabolism markers (BAP-S, CTX-S) as well as forearm BMD, were measured. The results of this study based on simple dose-effect analysis showed the relationship between increasing cadmium concentrations and an increased excretion of renal dysfunction markers and decreasing bone density. However, the results of the multivariate analysis did not indicate the association between exposure to cadmium and decrease in bone density. They showed that the most important factors that have impact on bone density are body weight and age in the female subjects and body weight and calcium excretion in males. Our investigation revealed that the excretion of low molecular weight proteins occurred at a lower level of cadmium exposure than the possible loss of bone mass. It seems that renal tubular markers are the most sensitive and significant indicators of early health effects of cadmium intoxication in the general population. The correlation of urinary cadmium concentration with markers of kidney dysfunction was observed in the absence of significant correlations with bone effects. Our findings did not indicate any effects of environmental cadmium exposure on bone density.

[Application of predictive model to estimate concentrations of chemical substances in the work environment]

BACKGROUND

Based on the Estimation and Assessment of Substance Exposure (EASE) predictive model implemented into the European Union System for the Evaluation of Substances (EUSES 2.1.), the exposure to three chosen organic solvents: toluene, ethyl acetate and acetone was estimated and compared with the results of measurements in workplaces.

MATERIAL AND METHODS

Prior to validation, the EASE model was pretested using three exposure scenarios. The scenarios differed in the decision tree of pattern of use. Five substances were chosen for the test: 1,4-dioxane tert-methyl-butyl ether, diethylamine, 1,1,1-trichloroethane and bisphenol A. After testing the EASE model, the next step was the validation by estimating the exposure level and comparing it with the results of measurements in the workplace. We used the results of measurements of toluene, ethyl acetate and acetone concentrations in the work environment of a paint and lacquer factory, a shoe factory and a refinery. Three types of exposure scenarios, adaptable to the description of working conditions were chosen to estimate inhalation exposure.

RESULTS

Comparison of calculated exposure to toluene, ethyl acetate and acetone with measurements in workplaces showed that model predictions are comparable with the measurement results. Only for low concentration ranges, the measured concentrations were higher than those predicted.

CONCLUSIONS

EASE is a clear, consistent system, which can be successfully used as an additional component of inhalation exposure estimation. If the measurement data are available, they should be preferred to values estimated from models. In addition to inhalation exposure estimation, the EASE model makes it possible not only to assess exposure-related risk but also to predict workers' dermal exposure.

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.

Physiologically-Based Toxicokinetic Modeling of Durene (1,2,3,5-Tetramethylbenzene) and Isodurene (1,2,4,5-Tetramethylbenzene) in Humans

OBJECTIVES

Physiologically-based toxicokinetic (PB-TK) models are developed to simulate absorption, distribution and excretion of xenobiotics. PB-TK models consist of several groups of compartments, where tissues are grouped together according to physiological parameters (tissue blood flows, tissue group volumes) and physicochemical properties (partition coefficients, metabolic constants). Tetramethylbenzene (TETMB), a mixture of its three isomers: prenitene (1,2,3,4-TETMB), isodurene (1,2,3,5-TETMB), and durene (1,2,4,5-TETMB) is an essential component of numerous commercial preparations of organic solvents. The aim of the study was to develop the PB-TK model for two TETMB isomers, durene and isodurene, in humans.

MATERIALS AND METHODS

The assumed PB-TK model groups organs and tissues into five physiological compartments: fat tissue, muscles, organs, liver, and brain. The brain has been considered as a separate compartment due to the potential neurotoxicity of TETMB. Water/air, oil/air and blood/air partition coefficients for durene and isodurene were measured in vitro. Tissue/air partition coefficients were calculated from values of olive/air and water/air partition coefficients and the average fat and water content in different tissues. Tissue/blood partition coefficients were calculated as a tissue/air quotient and the blood/air partition coefficient measured in vitro. The Michaelis-Menten constant (KM) values and maximum metabolism rate constant (VMAX) for selected metabolites of durene and isodurene were obtained in vitro using microsomal fraction of the human liver.

RESULTS

The developed model was validated against experimental data obtained earlier as a result of an 8-h exposure of volunteers to durene and isodurene vapors of 10 and 25 mg/m3. The prediction of both TETMB isomers concentration in blood as well as of the elimination rates of 2,4,5-TMBA and 2,3,5-TMBA were close to the results of experimental exposures.

CONCLUSIONS

Simulations of one working week inhalation exposure to aromatic hydrocarbons indicate that the elaborated PB-TK model may be used to predict the chemical distribution in different body compartments, based on physicochemical properties.

Interest of genotyping and phenotyping of drug-metabolizing enzymes for the interpretation of biological monitoring of exposure to styrene

In the field of occupational and/or environmental toxicology, the measurement of specific metabolites in urine may serve to assess exposure to the parent compounds (biological monitoring of exposure). Styrene is one of the chemicals for which biological monitoring programs have been validated and implemented in environmental and occupational medicine. However, inter-individual differences in the urinary excretion exist both for the main end-products (mandelic acid and phenylglyoxylic acid) and for its specific mercapturic acids (phenylhydroxyethylmercapturic acids, PHEMA). This limits to a certain extent the use of these metabolites for an accurate assessment of styrene exposure. In a group of 26 volunteers selected with relevant genotypes, and exposed to styrene vapours (50 mg/m3, 8 h) in an inhalation chamber, we evaluated whether genotyping or phenotyping relevant drug-metabolizing enzymes (CYP2E1, EPHX1, GSTM1, GSTT1 and GSTP1) may help to explain the observed inter-individual variability in the urinary metabolite excretion. Peripheral blood lymphocytes were used for genotyping and as reporter cells for the phenotyping of CYP2E1 and EPHX1. The GSTM1 genotype was clearly the most significant parameter explaining the variance in urinary PHEMA excretion (6-fold lower in GSTM1 null subjects; P < 0.0001) so that systematic GSTM1 genotyping should be recommended routinely for a correct interpretation of PHEMA urinary levels. Variant alleles CYP2E1*6 (7632T>A) and His113EPHX1 were associated with a significant reduction of, respectively, the expression (P = 0.047) and activity (P = 0.022) of the enzyme in peripheral blood lymphocytes. In combination with GSTM1 genotyping, the phenotyping approach also contributed to improve the interpretation of urinary results, as illustrated by the combined effect of CYP2E1 expression and GSTM1 allelic status that explained 77% of the variance in PHEMA excretion and allows the recommendation of mercapturates as specific and reliable biomarkers of exposure to styrene.