Fractionation of nickel species from airborne aerosols: practical improvements and industrial applications

Presently recommended methods for fractionation of airborne nickel dusts are laborious and time-consuming. A new method has been developed based on existing procedures of leaching nickel fractions from sample filters, and based on the principles of flow-injection analysis. A special sample filter holder has been constructed to be used in conjunction with the flow-injection system. In this system, soluble nickel compounds are extracted from the filter with ammonium citrate buffer, sulphidic nickel by peroxycitric acid, and metallic nickel by CuCl2/KCl. The final dissolution of the filter by HNO3/HCl results in the oxidic fraction. Endpoint determination of these fractions is performed by use of graphite-furnace atomic absorption spectrometry (GF-AAS). The analytical criteria of this method have been established, and the suitability of the method for application in the practice of industrial hygiene has been demonstrated.

Real-time PCR-analysis of the cytochrome P450 1B1 codon 432-polymorphism

The aim of the present study was to develop and validate a rapid assay for genotyping of CYP1B1 codon 432-polymorphism. The described method is a single tube assay and combines both rapid-cycle polymerase chain reaction (PCR) with real-time monitoring by amplification and generation of the melting profiles of an allele-specific fluorescent probe. With this method 300 samples were analysed from healthy, unrelated Germans. Genotype frequency determined for the mutated allele CYP1B1*2 was 0.40. The results show that genotyping of CYP1B1 codon 432-polymorphism with a real-time fluorescence PCR method is a rapid and reliable assay for the analysis of large numbers of samples.

Differential substrate behaviours of ethylene oxide and propylene oxide towards human glutathione transferase theta hGSTT1-1

The transformation of ethylene oxide (EO), propylene oxide (PO) and 1-butylene oxide (1-BuO) by human glutathione transferase theta (hGSTT1-1) was studied comparatively using 'conjugator' (GSTT1 + individuals) erythrocyte lysates. The relative sequence of velocity of enzymic transformation was PO > EO >> 1-BuO. The faster transformation of PO compared to EO was corroborated in studies with human and rat GSTT1-1 (hGSTT1-1 and rGSTT1-1, respectively) expressed by Salmonella typhimurium TA1535. This sequence of reactivities of homologous epoxides towards GSTT1-1 contrasts to the sequence observed in homologous alkyl halides (methyl bromide, MBr; ethyl bromide, EtBr; n-propyl bromide, PrBr) where the relative sequence MeBr >> EtBr > PrBr is observed. The higher reactivity towards GSTT1-1 of propylene oxide compared to ethylene oxide is consistent with a higher chemical reactivity. This is corroborated by experimental data of acid-catalysed hydrolysis of a number of aliphatic epoxides, including ethylene oxide and propylene oxide and consistent with semi-empirical molecular orbital modelings.

Determination of urinary thymidine glycol using affinity chromatography, HPLC and post-column reaction detection: a biomarker of oxidative DNA damage upon kidney transplantation

Reactive oxygen species are generated during ischaemia-reperfusion of tissue. Oxidation of thymidine by hydroxyl radicals (HO) leads to the formation of 5,6-dihydroxy-5,6-dihydrothymidine (thymidine glycol). Thymidine glycol is excreted in urine and can be used as biomarker of oxidative DNA damage. Time dependent changes in urinary excretion rates of thymidine glycol were determined in six patients after kidney transplantation and in six healthy controls. A new analytical method was developed involving affinity chromatography and subsequent reverse-phase high-performance liquid chromatography (RP-HPLC) with a post-column chemical reaction detector and endpoint fluorescence detection. The detection limit of this fluorimetric assay was 1.6 ng thymidine glycol per ml urine, which corresponds to about half of the physiological excretion level in healthy control persons. After kidney transplantation the urinary excretion rate of thymidine glycol increased gradually reaching a maximum around 48 h. The excretion rate remained elevated until the end of the observation period of 10 days. Severe proteinuria with an excretion rate of up to 7.2 g of total protein per mmol creatinine was also observed immediately after transplantation and declined within the first 24 h of allograft function (0.35+/-0.26 g/mmol creatinine). The protein excretion pattern, based on separation of urinary proteins on sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE), as well as excretion of individual biomarker proteins, indicated nonselective glomerular and tubular damage. The increased excretion of thymidine glycol after kidney transplantation may be explained by ischaemia-reperfusion induced oxidative DNA damage of the transplanted kidney.

[Occupational risk factors for bladder carcinoma. A case control study]

Aim of this case-control study, performed on 412 male bladder cancer cases and 414 controls with benign prostatic hyperplasia in a former area of coal, iron and steel industries in Germany, was to identify occupations with an increased bladder cancer risk. In bladder cancer cases, smokers were overrepresented (58.3%) compared to controls (35.2%). The percentage of patients who had stopped smoking for at least 10 years did not differ in cases (10.2%) and controls (9.7%). Significantly elevated smoking-adjusted bladder cancer odds ratios (MH) were observed in painters and lacquers (MH 2.24, 95% CI 1.07-5.13), chemistry-related occupations (MH 2.44, 95% CI 1.05-5.67), coke plant workers (MH 2.89, 95% CI 1.16-7.16) and hard coal miners (MH 2.33, 95% CI 1.52-3.58). Significantly decreased smoking-adjusted bladder cancer odds ratios (MH) were observed in businessmen (MH 0.64, 95% CI 0.45-0.92) and office personnel (MH 0.58, 95% CI 0.41-0.81). In these two groups a relevant exposure to occupational bladder carcinogens is not likely.

Pathological excretion patterns of urinary proteins in renal cell cancer patients exposed to trichloroethylene

A study was carried out to investigate urinary protein excretion patterns by means of SDS-polyacrylamide-gel-electrophoresis (SDS-PAGE) in renal cell cancer patients who had previously been exposed to high levels of trichloroethylene. Thirty-eight out of 41 (93%) renal cell cancer patients investigated had former extensive trichloroethylene exposure, but only 23 out of 50 (46%) renal cell cancer patients without a history of occupational exposure to trichloroethylene revealed urinary protein patterns indicative of toxic effects on the tubular system. One hundred controls without histories of overt renal disease and not occupationally exposed to trichloroethylene were examined in the same way; only 11 (11%) of them displayed protein excretion patterns indicative of damage to the renal tubule. These results are supported by alpha 1-microglobulin excretion data. The following conclusions are drawn: (1) Substantially more cases of tubular damage are found amongst renal cell carcinoma patients having been exposed to substantial levels of trichloroethylene over many years as compared with renal cell carcinoma patients not exposed to trichloroethylene. (2) The results support the view that chronic tubular damage is a precondition for the nephrocarcinogenic effect of trichloroethylene. (3) The findings indicate that urine protein patterns, on the basis of the SDS-PAGE methodology, represent a 'biological effect parameter' for the medical surveillance of persons occupationally exposed to trichloroethylene.

Toxicokinetics of p-tert-octylphenol in female DA/Han rats after single i.v. and oral application

Female DA/Han rats were administered p-tert-octylphenol [OP; p-(1,1,3,3-tetramethylbutyl)-phenol], either intravenously (5 mg/kg body wt.) or orally by gavage (50 or 200 mg/kg body wt.). After i.v. administration the blood concentration-time curve of OP was fitted to a tri-exponential model, resulting in a final half-life (gamma-phase) of 36.1 h. This contrasts to much more rapid eliminations previously reported in male Wistar rats. The oral bioavailability of 50 mg/kg OP was 12.3% and of 200 mg/kg 8.4%. The higher dose (200 mg kg) was absorbed slower than the smaller dose, probably due to low solubility of OP in aqueous media. Maximal OP blood levels in female DA/Han rats receiving 50 and 200 mg OP/kg body wt, were 4.5 and 3 times higher than previously reported in male Wistar rats. The blood concentration-time curves after oral administration of OP to female DA/Han rats revealed pronounced interindividual differences, indicating extensive enterohepatic circulation of OP in this rat strain. In contrast to male Wistar rats, after application of high doses of OP to female DA/Han rats the compound was not completely eliminated within 48 h: under these conditions some bioaccumulation might therefore occur. The experimental toxicokinetics of OP appears as a relevant subject to be integrated into extrapolation of toxicological data, from in vitro to in vivo, and into systems of risk assessment of endocrine modulating activity which are currently being developed.

Haemoglobin adducts of acrylonitrile and ethylene oxide in acrylonitrile workers, dependent on polymorphisms of the glutathione transferases GSTT1 and GSTM1

Fifty-nine persons with industrial handling of low levels of acrylonitrile (AN) were studied. As part of a medical surveillance programme an extended haemoglobin adduct monitoring [N-(cyanoethyl)valine, CEV; N-(methyl)valine. MV: N-(hydroxyethyl)valine, HEV] was performed. Moreover, the genetic states of the polymorphic glutathione transferases GSTM1 and GSTT1 were assayed by polymerase chain reaction (PCR). Repetitive analyses of CEV and MV in subsequent years resulted in comparable values (means, 59.8 and 70.3 microg CEV/1 blood; 6.7 and 6.7 microg MV/1 blood). Hence, the industrial AN exposures were well below current official standards. Monitoring the haemoglobin adduct CEV appears as a suitable means of biomonitoring and medical surveillance under such exposure conditions. There was also no apparent correlation between the CEV and HEV or CEV and MV adduct levels. The MV and HEV values observed represented background levels, which apparently are not related to any occupational chemical exposure. There was no consistent effect of the genetic GSTM1 or GSTT1 state on CEV adduct levels induced by acrylonitrile exposure. Therefore, neither GSTM1 nor GSTT1 appears as a major AN metabolizing isoenzyme in humans. The low and physiological background levels of MV were also not influenced by the genetic GSTM1 state, but the MV adduct levels tended to be higher in GSTT1- individuals compared to GSTT1 + persons. With respect to the background levels of HEV adducts observed, there was no major influence of the GSTM1 state, but GST- individuals displayed adduct levels that were about 1/3 higher than those of GSTT1 + individuals. The coincidence with known differences in rates of background sister chromatid exchange between GSTT1- and GSTT1 + persons suggests that the lower ethylene oxide (EO) detoxification rate in GSTT1- persons, indicated by elevated blood protein hydroxyethyl adduct levels, leads to an increased genotoxic effect of the physiological EO background.

Glutathione transferase alpha as a marker for tubular damage after trichloroethylene exposure

To investigate possible persistent nephrotoxic effects of trichloroethylene (TRI), a retrospective study was carried out on 39 workers exposed to high levels of TRI from 1956 to 1975. Total protein levels in urine, as well as serum and urine creatinine and serum urea were unchanged in comparison with the control. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) was applied to differentiate between tubular and/or glomerular dysfunction. Urinary excretion of alpha-1-microglobulin and glutathione transferase (GST) alpha, as markers of proximal tubular damage, were correlated with the SDS-PAGE patterns of urinary proteins both in the TRI exposed and the control group. GST alpha was found in elevated concentrations in the urine of the TRI-exposed workers. No increase of urinary GST alpha was observed in the control group, even when alpha-1-microglobulin was elevated as a result of non-toxic damage. Both in the control and exposed groups, GST pi, a marker of distal tubular damage, was in the normal range. The results show that chronic exposure to high doses of TRI causes persistent changes to the proximal tubular system of the kidney and that GST alpha excretion into the urine is a marker well suited for quantitation of the extent of renal damage.

Occurrence of urinary tract tumors in miners highly exposed to dinitrotoluene

Between 1984 and 1997, six cases of urothelial cancer and 14 cases of renal cell cancer occurred in a group of 500 underground mining workers in the copper-mining industry of the former German Democratic Republic, with high exposures to explosives containing technical dinitrotoluene. Exposure durations ranged from 7 to 37 years, and latency periods ranged from 21 to 46 years. The incidences of both urothelial and renal cell tumors in this group were much higher than anticipated on the basis of the cancer registers of the German Democratic Republic by factors of 4.5 and 14.3, respectively. The cancer cases and a representative group of 183 formerly dinitrotoluene-exposed miners of this local industry were interviewed for their working history and grouped into four exposure categories. This categorization of the 14 renal cell tumor cases revealed no dose-dependency concerning explosives in any of the four exposure categories and was similar to that of the representative group of employees, whereas the urothelial tumor cases were predominantly confined to the high-exposure categories. Furthermore, all identified tumor patients were genotyped by polymerase chain reaction, using lymphocyte DNA, regarding their genetic status of the polymorphic xenobiotic metabolizing enzymes, including the N-acetyltransferase 2 and the glutathione-S-transferases M1 and T1. This genotyping revealed remarkable distributions only for the urothelial tumor cases, who were exclusively identified as "slow acetylators." This points to the possibility of human carcinogenicity of dinitrotoluene, with regard to the urothelium as the target tissue.

Determination of glutathione transferase (GSTT1-1) activities in different tissues based on formation of radioactive metabolites using 35S-glutathione

A new system has been developed to determine enzyme activities of glutathione transferase theta (GSTT1-1) based on radiometric product detection resulting from the enzymic reaction of methyl chloride with 35S-labelled glutathione. In principle, the method is universally applicable for determination of glutathione transferase activities towards a multiplicity of substrates. The method distinguishes between erythocyte GSTT1-1 activities of human 'non-conjugators', 'low conjugators' and 'high conjugators'. Application to cytosol preparations of livers and kidneys of male and female Fischer 344 and B6C3F1 mice reveals differential GSTT1-1 activities in hepatic and renal tissues. These ought to be considered in species-specific modellings of organ toxicities of chlorinated hydrocarbons.

Renal cell cancer correlated with occupational exposure to trichloroethene

A previous cohort-study in a cardboard factory demonstrated that high and prolonged occupational exposure to trichloroethene (C2HCl3) is associated with an increased incidence of renal cell cancer. The present hospital-based case/control study investigates occupational exposure in 58 patients with renal cell cancer with special emphasis on C2HCl3 and the structurally and toxicologically closely related compound tetrachloroethene (C2Cl4). A group of 84 patients from the accident wards of three general hospitals in the same area served as controls. Of the 58 cases, 19 had histories of occupational C2HCl3 exposure for at least 2 years and none had been exposed to C2Cl4; of the 84 controls, 5 had been occupationally exposed to C2HCl3 and 2 to C2Cl4. After adjustment for other risk factors, such as age, obesity, high blood pressure, smoking and chronic intake of diuretics, the study demonstrates an association of renal cell cancer with long-term exposure to C2HCl3 (odds ratio 10.80; 95% CI: 3.36-34.75).

Glutathione transferase T1 and M1 genotype polymorphism in the normal population of Shanghai

Glutathione transferases are known to be important enzymes in the metabolism of xenobiotics. In humans genetic polymorphisms have been reported for the hGSTM1 and hGSTT1 genes leading to individual differences in susceptibility towards toxic effects, such as cancer. This study describes the distribution of the two polymorphisms of hGSTT1 and hGSTM1 in the normal Chinese population of Shanghai. Out of 219 healthy individuals having been genotyped for GSTT1 and GSTM1, 108 (49%) were identified to be homozygously deficient for the GSTT1 gene and 107 (49%) for the GSTM1 gene.

Mutagenic properties of 1,2,3,4-tetrahydronaphthaline-1-hydroperoxide, a model compound for organic peroxides in Diesel exhaust

The genotoxicity of the organic peroxide 1,2,3,4-tetrahydronaphthaline-1-hydroperoxide (or tetraline-1-hydroperoxide, THP) was investigated in the Ames assay without a metabolic activating system using Salmonella typhimurium strains TA 98, TA 100, and TA 102. THP served as a model compound for higher organic peroxides, which can arise from autoxidation of hydrocarbons, e.g. in Diesel exhaust. While THP induced no mutagenic response in S. typhimurium TA 98, it was directly mutagenic in strains TA 100 and TA 102. These data, along with findings on mutagenic properties of other alkyl hydroperoxides, suggest that such compounds deserve further investigation regarding their genotoxic potential and occurrence in the environment.

The carcinogenic risk of ethene (ethylene)

On occasion of the 25th year of publication of Toxicologic Pathology, the Editor has asked for a report about recent progress in the area addressed by an article entitled “Olefinic Hydrocarbons: A First Risk Estimate,” one of the top 10 most frequently cited papers of the journal (3). Because general issues of risk assessment have very recently been addressed in this journal (6), I will focus on new specific aspects of ethene carcinogenicity.

Urothelial cancer of the bladder in an area of former coal, iron, and steel industries in Germany: a case-control study

In a case-control study performed in an area of former coal, iron, and steel industries, the professional and lifestyle histories of 412 male urothelial bladder cancer inpatients (cases) and 414 inpatients with benign prostatic hyperplasia (controls) were investigated. Smoking habits were identified as the main confounder for occupational bladder cancer risk. Two hundred and forty (58.3%) of the bladder cancer inpatients and 146 (35.3%) of the inpatients with benign prostatic hyperplasia were smokers. The percentage of ex-smokers in the bladder cancer cases was 10.2%; the percentage of ex-smokers in the controls was 9.7%. Smoking-adjusted Mantel-Haenszel estimates of the odds ratios (OR&infMH;) for bladder cancer were elevated in underground hard-coal miners (OR&infMH; =2. 54, 95% CI =[1.64; 3.93]), chemical workers (OR&infMH; =2.16, 95% CI =[0.87; 5.38]), painters/varnishers (OR&infMH; = 2.42, 95% CI =[1. 05; 5.57]), technicians (OR&infMH; = 1.99, 95% CI =[0.95; 4.16]), and foundry workers (OR&infMH; = 2.22, 95% CI = [0.53; 9.08]). Administrative officers had significantly lower smoking-adjusted odds ratios (OR&infMH; = 0.61, 95% CI = [0.42; 0.88]). Although statistically not significant, the results of the Breslow-Day test of homogeneity of the odds ratios over the strata are compatible with interactions between tobacco smoking and the occupations of underground hard-coal miners (chi(2)&infBD; = 4.91, p=0.07) and chemical workers (chi(2)&infBR; = 3.32, p=0.06).

Modulation of prostaglandin H synthase-2 mRNA expression by 2,3,7,8-tetrachlorodibenzo-p-dioxin in mice

Prostaglandin endoperoxide H synthases (PGHS-1 and PGHS-2) catalyze an intermediate step in the biosynthesis of prostaglandins and thromboxanes. Recently, it was observed that 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) modulates the expression of PGHS-2 mRNA in different cell lines. The main aim of this study was to examine whether PGHS-2 mRNA expression can be changed by acute TCDD in vivo and, second, we were also interested in whether modulation of PGHS-2 is mediated by the aryl hydrocarbon receptor (AhR) which is known to be involved in the transcriptional control of TCDD-induced phase 1 and phase 2 enzymes. Initially C57BL/6J mice were treated with a single dose of 10,000 ng TCDD/kg and the PGHS-1 and PGHS-2 mRNAs were analyzed in liver, lung, thymus, kidney, and spleen. In all tissues examined the expression of PGHS-1 mRNA was not affected by TCDD. However, TCDD treatment enhanced the PGHS-2 mRNA levels in lung and spleen. No effect of TCDD on PGHS-2 expression was found in liver and kidney. For dose-response studies C57BL/6J and DBA/2J mice were treated for 24 h with various doses of TCDD (1-50,000 ng/kg) and the PGHS-2 mRNA increases were analyzed in lungs and spleens. A significant increase of PGHS-2 mRNA in lungs of C57BL/6J mice was found at a dose of 100 ng TCDD/kg, whereas a nearly 100-fold higher TCDD dose was needed to increase PGHS-2 in DBA/2J mice. A similar dose-dependent induction of PGHS-2 was found in spleens of C57BL/6J mice; however, no significant increase of PGHS-2 was found in spleens of DBA/2 mice. These results indicate an involvement of AhR in TCDD-mediated changes of PGHS-2 expression. This suggestion is supported by studies in AhR-deficient animals which showed that TCDD had no effect on PGHS-2 mRNA. When changes of PGHS-2 mRNA expression are compared with those of CYP1A1 between 4 and 72 h after TCDD, it is noteworthy that TCDD led to a delayed and more transient increase of PGHS-2. These data suggest that the mechanism of modulation of both genes by TCDD may be different.