Feasibility of Biological Effective Monitoring of Chrome Electroplaters to Chromium through Analysis of Serum Malondialdehyde

BACKGROUND

Great concern about occupational exposure to chromium (Cr [VI]) has been reported due to escalated risk of lung cancer in exposed workers. Consequences of occupational exposure to Cr (VI) have been reported as oxidative stress and lung tissue damage.

OBJECTIVE

To investigate the feasibility of biological effect monitoring of chrome electroplaters through analysis of serum malondialdehyde (MDA).

METHODS

90 workers directly involved in chrome electroplating---categorized into three equal groups based on their job as near bath workers, degreaser, and washers---and 30 workers without exposure to Cr (VI), served as the control group, were studied. Personal samples were collected and analyzed according to NIOSH method 7600. Serum MDA level was measured by HPLC using a UV detector.

RESULTS

Median Cr (VI) exposure level was 0.38 mg/m(3) in near bath workers, 0.20 mg/m(3) in degreasers, and 0.05 mg/m(3) in washers. The median serum MDA level of three exposed groups (2.76 μmol/L) was significantly (p<0.001) higher than that in the control group (2.00 μmol/L). There was a positive correlation between electroplaters' level of exposure to Cr (VI) and their serum MDA level (Spearman's ρ 0.806, p<0.001).

CONCLUSION

Serum MDA level is a good biomarker for the level of occupational exposure to Cr (VI) in electroplaters.

Occupational exposure of petroleum depot workers to BTEX compounds

BACKGROUND

Benzene, toluene, ethylbenzene and xylene (BTEX) are the most important toxic volatile compounds in the air and could be easily absorbed through the respiratory tract. In recent years, the risk of exposure to BTEX compounds, especially benzene as a carcinogen, has been considered in petroleum depot stations.

OBJECTIVE

To assess the occupational exposure of petroleum depot workers in Iran to BTEX compounds.

METHODS

After completing a questionnaire and assessing occupational exposure to BTEX compounds, 78 (46 exposed and 32 non-exposed) depot workers were randomly selected to participate in this study. Air sampling and analysis of BTEX was conducted according to the NIOSH method No. 1501. Analysis of urinary hippuric acid, as an indicator of toluene exposure, was carried out according to NIOSH method No. 8300. Personal monitoring of the high exposure group to BTEX compounds was repeated to verify the results obtained in the first phase of the monitoring.

RESULTS

Among the 9 operating groups studied, occupational exposure to benzene and toluene was higher in quality control and gasoline loading operators-the median exposure ranged from 0.16 to 1.63 ppm for benzene and 0.2 to 2.72 ppm for toluene. Median exposure of other group members to BTEX compounds was below the detection limit of analytical method (0.07, 0.06, 0.05, and 0.05 ppm, respectively). The level of toluene exposure measured showed correlation with neither post-shift urinary hippuric acid (Spearman's rho = 0.128, p = 0.982) nor with the difference between post- and pre-shift urinary hippuric acid (Spearman's rho = 0.089, p = 0.847) in depot operational workers.

CONCLUSION

Gasoline loading operators are exposed to a relatively high level of benzene.

Effects of nitrogen oxides on natural killer cells in glass craftsmen and braziers

OBJECTIVES

To assess the effect of exposure to nitrogen oxides on peripheral blood natural killer cells.

METHODS

Groups of glass craftsmen and braziers exposed to nitrogen oxides and non-exposed controls were studied. Air concentrations of nitrogen oxides were measured. Mononuclear cells isolated from peripheral blood samples were assayed for natural killer cell activity with K562 target cells in a 51Cr release assay and the percentage of natural killer cells (CD16) was measured by flow cytometry.

RESULTS

Braziers were exposed to 1.2 ppm nitrogen dioxide and 8.6 ppm nitric oxide and glass craftsmen to 2.9 ppm nitrogen dioxide and 26.5 ppm nitric oxide. The natural killer cell activity of exposed workers was significantly lower than in non-exposed controls (P < 0.05 ANOVA Scheffe test). The percentage of natural killer cells in glass craftsmen was significantly greater than in controls (P < 0.05 ANOVA Scheffe test). Regression of natural killer cell activity against age, smoking habit, number of years worked and current exposure to nitrogen dioxide and nitric oxide gases was not significant. The percentage of natural killer cells was not significantly correlated with age, smoking habit, or numbers of years worked, but was significantly related to air concentrations of nitrogen dioxide (P < 0.01) and nitric oxide (P < 0.001).

CONCLUSION

Natural killer cell activity and the percentage of natural killer cells in peripheral blood cells were altered in workers exposed to nitrogen oxides.

Purification and properties of Aerococcus viridans lactate oxidase

Lactate oxidase was purified from cells of Aerococcus viridans by a procedure which utilized ammonium sulfate fractionation, DEAE Sepharose CL-6B chromatography, and Sephadex G-100 chromatography. The final preparation was homogeneous by SDS-polyacrylamide gel electrophoresis. The enzyme appears to be a tetramer with a subunit molecular weight of 44,000 and utilizes FMN as a cofactor. The enzyme was highly specific for L-lactate. D-lactate, glycolate, and D,L-2-hydroxybutyrate were not oxidized by the enzyme but were competitive inhibitors. The enzyme could be irreversibly inactivated by incubation with bromopyruvate. This inactivation appears to involve a covalent modification near the active site of the enzyme; however, the flavin cofactor is not the site of this modification.

Studies on the properties of highly purified cytochrome P-448 and its dependent activity benzo[a]pyrene hydroxylase, from Saccharomyces cerevisiae

The yeast Saccharomyces cerevisiae, produces a cytochrome P-450 enzyme with a Soret peak in the reduced-CO difference spectrum at 448 nm. The enzyme purified to homogeneity (88-97% pure on a specific content basis) has a molecular wt. of 55 500 as determined by SDS-PAGE. Amino acid analysis of yeast cytochrome P-448 revealed 407 amino acid residues per molecule with a 43% complement of hydrophobic residues. Although the number of residues is smaller than cytochrome P-448 enzymes from mammalian sources, the percentage of hydrophobic residues is almost identical. Estimation of the haem content of yeast cytochrome P-448 showed that one haem group was present per molecule. Phospholipid was present at very low levels. The molecular wt. of the polypeptide chain plus an estimated 5-6 units of hexose and of hexosamine is in good agreement with the molecular wt. value obtained from SDS-PAGE. A reconstituted system of purified cytochrome P-448, purified NADPH-cytochrome P-450 (c) reductase and phospholipid showed aryl hydrocarbon hydroxylase activity towards benzo[a]pyrene. Both protein components, NADPH and dilauroyl phosphatidylcholine (or emulgen 911) were necessary for full activity. The NADPH requirement could be replaced by cumene hydroperoxide or H2O2 generated in situ from a glucose oxidase system; in each case Vmax is increased, but the apparent affinity for benzo[a]pyrene, as measured by an increased Km, is lowered. The spin state of purified yeast cytochrome P-448 was 94% low spin (22 degrees C) as determined from the temperature-dependent spin-state equilibrium. The addition of benzo[a]pyrene to this enzyme resulted in a change to higher spin state (18% high spin at 22 degrees C). Equilibrium gel filtration analysis of the number of benzo[a]pyrene binding sites per mole of enzyme monomer showed a value of 1 for purified yeast cytochrome P-448 and 6 for this enzyme in microsomal form. The corresponding values for purified and microsomal cytochrome P-450 from phenobarbital-pretreated rats are 1 and 6, respectively. However, purified cytochrome P-448 from beta-naphthoflavone-induced rats gave a value of 6 benzo[a]pyrene binding sites. Type I binding spectra with purified yeast cytochrome P-448 were observed with benzo[a]pyrene, lanosterol, ethylmorphine, dimethylnitrosamine, sodium phenobarbitone and perhydrofluorene. Type II spectral changes were observed with imidazole, aniline and benzphetamine. Cytochrome P-448 from Saccharomyces cerevisiae is identified as a distinct enzyme of the P-450 family. This enzyme however has many properties in common with cytochrome P-448 from mammalian sources.(ABSTRACT TRUNCATED AT 400 WORDS)