Comparison of biomarkers in workers exposed to 2,4,6-trinitrotoluene

2,4,6-Trinitrotoluene (TNT) is an important occupational and environmental pollutant. In TNT-exposed humans, notable toxic manifestations have included aplastic anaemia, toxic hepatitis, cataracts, hepatomegaly, and liver cancer. Therefore, methods were developed to biomonitor workers exposed to TNT. The workers were employed in a typical ammunition factory in China. The external dose (air levels and skin exposure), the internal dose (urinary metabolites), the biologically effective dose (haemoglobin adducts, urinary mutagenicity), biological effects (chromosomal aberrations and health effects), and individual susceptibility (genotypes of xenobiotic-metabolizing enzymes) were determined. Haemoglobin-adducts of TNT, 4-amino-2,6-dinitrotoluene (4ADNT) and 2-amino-4,6-dinitrotoluene (2ADNT), and the urinary metabolites of TNT, 4ADNT and 2ADNT, were found in all workers and in some controls. The levels of the haemoglobin-adducts or the urinary metabolites correlated weakly with the skin or air levels of TNT. The urinary mutagenicity determined in a subset of workers correlated strongly with the levels of 4ADNT and 2ADNT in urine. The haemoglobin-adducts correlated moderately with the urinary metabolites and with the urinary mutagenicity. The genotypes of glutathione S-transferases (GSTM1, GSTT1, GSTP1) and N-acetyltransferases (NAT1, NAT2) were determined. In general, the genotypes did not significantly influence the haemoglobin-adduct levels and the urine metabolite levels. However, TNT-exposed workers who carried the NAT1 rapid acetylator genotype showed an increase in urinary mutagenicity and chromosomal aberrations as compared with slow acetylators. The haemoglobin adduct 4ADNT was significantly associated with a risk of hepatomegaly, splenomegaly and cataract; urine metabolites and genotypes were not associated with health effects. These results indicate that a set of well-selected biomarkers may be more informative regarding exposure and effect than routinely performed chemical measurements of pollutants in the air or on the skin.     

Determination of hemoglobin adducts in workers exposed to 2,4,6-trinitrotoluene

2,4,6-Trinitrotoluene (TNT) is an important occupational and environmental pollutant. TNT can be taken up through the skin and by inhalation. It is therefore essential to have fast and reliable methods to monitor human exposure. In rat experiments, it has been shown that TNT binds covalently to blood proteins and to tissue proteins. Hemoglobin (Hb) adducts of TNT are markers for the internal dose and possibly for the toxic effects of TNT, e.g. cataracts. In the present paper we introduce a new efficient method to quantify Hb adducts of TNT. Precipitated Hb was hydrolyzed with base in the presence of the surrogate internal standard 3,5-dinitroaniline (35DNA). The released 2-amino-4,6-dinitrotoluene (2ADNT) and 4-amino-2,6-dinitrotoluene (4ADNT) were quantified against 35DNA by gas chromatography-mass spectrometry with negative-ion chemical ionization. Hb of 50 workers and controls from a Chinese munition factory were investigated. The Hb adduct levels ranged from 3.7 to 522 ng for 4ADNT and from 0 to 14.7 ng for 2ADNT per gram of Hb. However, in control samples from Germany no Hb adducts of 4ADNT or 2ADNT could be found.     

Detection of 2,4,6-trinitrotoluene in seawater using a reversed-displacement immunosensor

Reported in this study are the experimental design and results of an immunosensor for the detection of the explosive, 2,4,6-trinitrotoluene (TNT) in seawater using a reversed-displacement format. This reversed-displacement immunosensor methodology has successfully measured TNT in seawater by direct injection, eliminating the need for preconcentration or pretreatment of samples. A microcolumn containing an Affi-Gel resin derivatized with a 2,4,6-trinitrobenzene (TNB) moiety and a fluorophore-labeled anti-TNT antibody composed the immunoassay reactive chamber. Fluorophore-labeled anti-TNT antibody was incubated with the modified Affi-Gel resin until binding equilibrium was reached. Under a constant flow, samples containing TNT were introduced into the flow stream displacing the fluorophore-labeled TNT antibody. Limits of detection were 2.5ng/mL or part-per-billion (ppb) for TNT in saline buffer and 25ppb in seawater with an analysis time of 10 min. Two anti-TNT antibodies with differing binding affinities were compared in the reversed-displacement assay format, and a correlation between affinity and detection limits was observed. Furthermore, we have demonstrated that the reversed-displacement format can be used to screen seawater samples containing TNT, remains effective after dozens of cycles, and provides significant fluorescence response before regeneration is required.     

Urinary metabolites and health effects in workers exposed chronically to chloronitrobenzene

For workers exposed to 4-chloronitrobenzene (4CNB), the major metabolites were determined. Urine were analysed before and after acid hydrolysis to qualify the free and conjugated metabolites of 4CNB. Three conjugated metabolites were identified in exposed workers: the mercapturic acid N-acetyl-S-(4-nitrophenyl)-L-cysteine (NANPC) was the only metabolite detected in non-hydrolysed urine, and accounted for approximately 51% of the total metabolites detected. The two remaining metabolites 4-chloroaniline (4CA) and 2-chloro-5-nitrophenol (CNP) were identified as cleavage products in hydrolysed urine, and accounted for approximately 18 and 30% of the total metabolites detected, respectively. No metabolites were found in factory controls within the limits of quantitation (LOQ) of the assay. There is a moderate correlation between NANPC and both 4CA and CNP. The correlation between 4CA and CNP is minor. The correlation between the total metabolites and both 4CA and CNP are good. The best correlation was found between the total metabolites and NANPC. There is a moderate inverse correlation between age and the creatinine levels. The raw metabolite levels CNP and NANPC decrease with age. 4CA, NANPC and the total metabolite levels correlate with the haemoglobin adduct levels . The urine metabolites increase and correlate significantly with the creatinine levels. NANPC is the most appropriate biomarker in the urine for a recent absorbed dose of 4CNB, since NANPC reflects the levels of 4CA and CNP and is the most prevalent metabolite detected in all the exposed workers.     

Determination of laccase gene expression during degradation of 2,4,6-trinitrotoluene and its catabolic intermediates in Trametes versicolor

We have cloned a laccase gene fragment isolated from a Trametes versicolor strain in Korea. It showed high similarity in nucleotide sequences when compared with other fungal laccases. TNT (2,4,6-trinitrotoluene), a widely used explosive, was transformed rapidly by T. versicolor. When TNT and its catabolic intermediates were added to the fungal culture, they were transformed during the first few hours and the expression level of the laccase gene was increased during the early stage of cultivation.     

Biomarkers of exposure,effect, and susceptibility in workers exposed to chloronitrobenzenes

Biomonitoring methods were applied to workers exposed to high levels of chloronitrobenzenes. The external dose, internal dose, biologically effective dose, and biological effects were determined. Individual susceptibility was assessed by analyzing genetic polymorphisms of glutathione S-transferases M1, P1 and T1, and N-acetyltransferases 1 and 2. When the markers of exposure and susceptibility were compared with the frequency of chromosomal aberrations, clinical blood and urine parameters, and health effects typical of chloronitrobenzenes exposure, only a few of the comparisons were statistically significant. A statistically significantly higher frequency of chromosomal aberrations was detected in workers with a high level of hemoglobin-adducts.     

Association between metabolic gene polymorphisms and susceptibility to peripheral nerve damage in workers exposed to n-hexane: A preliminary study

Chronic exposure to n-hexane may result in peripheral neuropathy. 2,5-Hexanedione (2,5-HD) has been identified as a toxic metabolite of n-hexane. The CYP2E1, CYP1A1 and GST genes are involved in the formation of 2,5-hexanedione from n-hexane as well as the elimination of 2,5-HD-formed electrophile, and these genes are highly polymorphic in the general population. A nested case-control study in an industrial cohort was conducted to evaluate the associations between polymorphisms in these metabolic genes and n-hexane-induced peripheral nerve damage. The study subjects included 22 cases, who worked in a printing factory with symptoms of peripheral nerve damage, and 163 controls, who came from the same factory of cases. DNA was extracted from blood samples and genotyping was conducted for CYP2E1 Pst, CYP2E1 Dra, CYP2E1 Ins96, CYP1A1 Msp, GSTT1 null, GSTM1 null and GSTP1 105V. Unconditional logistic regression was applied to estimate the odds ratio and 95% confidence intervals. There were no significant differences between the two groups regarding age, sex, smoking and alcohol status. A significant association between Dra polymorphism and peripheral nerve damage was found. The frequency of CYP2E1 Dra homozygous mutation in the case group (18.2%) was higher than that in the control group (3.7%, p=0.015). Individuals with homozygote genotype (CC) of CYP2E1 Dra had a significantly higher risk of peripheral nerve damage compared with those with DD genotype (adjusted OR = 5.58, 95% CI = 1.32-23.65) after n-hexane exposure duration, sex, age, smoking and alcohol status were adjusted. No significant association was found that CYP2E1 Pst, CYP2E1 Ins96, CYP1A1 Msp, GSTT1, GSTM1, GSTP gene polymorphisms associated with the susceptibility of peripheral nerve damage. These findings suggested that CYP2E1 gene might increase the susceptibility to n-hexane-induced peripheral damage.     

Phytodetoxification of the environmental pollutant and explosive 2,4,6-trinitrotoluene

Our recent study highlights the role of 2 glutathione transferases (GSTs) in the detoxification of the environmental pollutant, 2,4,6-trinitrotoluene (TNT) in Arabidopsis thaliana. TNT is toxic and highly resistant to biodegradation in the environment, raising both health and environmental concerns. Two GSTs, GST-U24 and GST-U25, are upregulated in response to TNT treatment, and expressed predominantly in the root tissues; the site of TNT location following uptake. Plants overexpressing GST-U24 and GST-U25 exhibited significantly enhanced ability to withstand and detoxify TNT, and remove TNT from contaminated soil. Analysis of the catalytic activities of these 2 enzymes revealed that they form 3 TNT-glutathionyl products. Of particular interest is 2-glutathionyl-4,6-dinitrotoluene as this represents a potentially favorable step toward subsequent degradation and mineralization of TNT. We demonstrate how GSTs fit into what is already known about pathways for TNT detoxification, and discuss the short and longer-term fate of TNT conjugates in planta.     

Association between metabolic gene polymorphisms and susceptibility to peripheral nerve damage in workers exposed to n-hexane: A preliminary study

Abstract

Chronic exposure to n-hexane may result in peripheral neuropathy. 2,5-Hexanedione (2,5-HD) has been identified as a toxic metabolite of n-hexane. The CYP2E1, CYP1A1 and GST genes are involved in the formation of 2,5-hexanedione from n-hexane as well as the elimination of 2,5-HD-formed electrophile, and these genes are highly polymorphic in the general population. A nested case-control study in an industrial cohort was conducted to evaluate the associations between polymorphisms in these metabolic genes and n-hexane-induced peripheral nerve damage. The study subjects included 22 cases, who worked in a printing factory with symptoms of peripheral nerve damage, and 163 controls, who came from the same factory of cases. DNA was extracted from blood samples and genotyping was conducted for CYP2E1 Pst, CYP2E1 Dra, CYP2E1 Ins96, CYP1A1 Msp, GSTT1 null, GSTM1 null and GSTP1 105V. Unconditional logistic regression was applied to estimate the odds ratio and 95% confidence intervals. There were no significant differences between the two groups regarding age, sex, smoking and alcohol status. A significant association between Dra polymorphism and peripheral nerve damage was found. The frequency of CYP2E1 Dra homozygous mutation in the case group (18.2%) was higher than that in the control group (3.7%, p=0.015). Individuals with homozygote genotype (CC) of CYP2E1 Dra had a significantly higher risk of peripheral nerve damage compared with those with DD genotype (adjusted OR?=?5.58, 95% CI?=?1.32–23.65) after n-hexane exposure duration, sex, age, smoking and alcohol status were adjusted. No significant association was found that CYP2E1 Pst, CYP2E1 Ins96, CYP1A1 Msp, GSTT1, GSTM1, GSTP gene polymorphisms associated with the susceptibility of peripheral nerve damage. These findings suggested that CYP2E1 gene might increase the susceptibility to n-hexane-induced peripheral damage.     

激光及γ射线对有丝分裂染色体畸变感应现象的比较

波长514nm的激光照射可用于研究激光导致有丝分裂染色体畸变的效应。本文提供了一种新的辐照系统,能用于研究突变的感应现象,并与从γ-线辐射源获得的结果进行了比较。 Abstract:Laser irradiation at wavelength 514 nm was used to study the effect of lasers in inducing chromosomal aberrations at mitosis.This study offers a new radiation system which could be used for the induction of mutations.Results are compared with those obtained from studies using γ-rays as irradiation source.     

Analysis of chromosomal aberrations in men occupationally exposed to cement dust

Cement industry is considered as a major pollution problem on account of dust and particulate matter emitted at various steps of cement manufacture. Cement dust consists of many toxic constituents. The workers who are employed in cement industries are exposed to cement dust for long periods. Therefore, it is mandatory to evaluate the mutagenic effects of occupational exposure to cement dust in such workers. In the present study, we analyzed the samples of 124 male workers including 59 smokers and 65 non-smokers who were employed in cement industry for a period of 1–17 years. For comparison, 106 controls (including 47 smokers and 59 non-smokers) of the same age group and socio-economic status were also studied. Controls had no exposure to cement dust or any known physical or chemical agent. A significant increase in the incidence of chromosomal aberrations was observed in the exposed group when compared to the control group. The results were analyzed separately for non-smokers and smokers. The chromosomal damage was more pronounced in the smokers when compared with the non-smokers both in control and exposed groups. A significant increase in the frequency of chromosomal aberrations was also observed with increase in age in both control and exposed subjects.     

Urinary hydroxylated metabolites of polycyclic aromatic hydrocarbons as biomarkers of exposure in asphalt workers

Background. Fumes and vapours released during laying of hot asphalt mix have been recognised as a major source of exposure for asphalt workers. Objectives. We investigated the relationships between inhalation exposure to asphalt emissions and urinary biomarkers of polycyclic aromatic hydrocarbons (PAHs) in asphalt workers (AW, n=75) and in ground construction workers (CW, n=37). Methods. Total polyaromatic compounds (PAC) and 15 priority PAHs in inhaled air were measured by personal sampling. Hydroxylated PAH metabolites (OH-PAHs) (2-naphthol, 2-hydroxyfluorene, 3-hydroxyphenanthrene, 1-hydroxypyrene, 6-hydroxychrysene and 3-hydroxybenzo[a]pyrene) were determined in urine spot samples collected in three different times during the work week. Results. Median vapour-phase PAC (5.5 µg m^-3), PAHs (≤50 ng m^-3) and OH-PAHs (0.08-1.11 µg l^-1) were significantly higher in AW than in CW, except in the cases of air naphthalene and 2-naphthol. Airborne levels of particle-phase contaminants were similar in the two groups and much lower than vapour-phase levels; metabolites of particulate PAHs were never found in quantifiable amounts. An appreciable increase in OH-PAH levels during the work day and work week was found in AW; median levels for 2-hydroxyfluorene, 3-hydroxyphenanthrene and 1-hydroxypyrene were, respectively, 0.29, 0.08 and 0.18 at baseline; 0.50, 0.18 and 0.29, pre-shift; 1.11, 0.44 and 0.44 µg l^-1, post-shift. Each OH-PAH exhibited a characteristic profile of increase, reflecting differences in half-lives of the parent compounds. In non-smoking subjects, positive correlations were found between vapour-phase PAC or PAHs and OH-PAHs both in pre- and post-shift samples (0.34 ≤ r≤69). Smokers exhibited 2-5-fold higher OH-PAHs than non-smokers, at any time and at both workplaces. Conclusions. Our results suggest that OH-PAHs are useful biomarkers for monitoring exposure to asphalt emissions. The work-related exposure to PAC and PAHs was low in all AW, but urinary metabolites reflected exposure satisfactorily.     

Differences in the biotransformation of 2,4,6-trinitrotoluene (TNT) between wild and axenically grown isolates of Myriophyllum aquaticum

The aim of this study was to demonstrate the potential for aquatic plants and their associated microbes to bioremediate wetland sites contaminated with 2,4,6-trinitrotoluene (TNT). The transformation of TNT was studied using both wild and axenically grown isolates of Myriophyllum aquaticum (parrot feather). Differences in TNT transformation rates and nitroaromatic metabolites were observed between different plants. The wild isolates, containing a consortium of associated microorganisms, transformed TNT into 2-amino-4,6-dinitrotoluene (2-A-DNT) and 4-amino-2,6-dinitrotoluene (4-A-DNT) via 2- and 4-hydroxylamino-dinitrotoluene, which were detected as intermediates. The wild M. aquaticum also converted the metabolites, 2-A-DNT and 4-A-DNT, into low levels of 2,4-diaminotoluene (2,4-DAT). The axenically grown plants, containing no cultureable microorganisms, also transformed TNT into 2-A-DNT and 4-A-DNT, but at a much lower rate than that observed for the wild isolates. Unlike the wild plants, axenically grown M. aquaticum could not transform either 2-A-DNT or 4-A-DNT into 2,4-DAT over the incubation period. The differences in the performance between these plants could indicate that plant-associated microorganisms assisted in the overall transformation of TNT. For each plant, unidentifiable metabolites were observed and the soluble monoamino-derivatives present in the wild and axenic medium accounted for 14 and 7% of the initial TNT concentration, respectively. Thus, the majority of nitroaromatic derivatives remained associated with the plant tissues. Furthermore, only 7 and 3% of the initial TNT concentration were extracted as monoamino-derivatives from the tissues of the wild and axenically grown plants, respectively.     

以大肠杆菌为底盘细胞构建XylR-Pu线路检测2,4,6-三硝基甲苯

目的:恶臭假单胞菌中的TOL质粒上的XylR-Pu是经典的甲苯代谢通路,在甲苯类化合物存在时,调控蛋白XylR可以特异性的激活Pu启动子,进而启动相应甲苯代谢通路的表达。基于合成生物学的思想,优化设计此通路并导入遗传背景清楚、操作简单的大肠杆菌中构建全细胞生物传感器,用于检测环境污染物2,4,6-三硝基甲苯(TNT)。方法:以pETDuet-1为载体骨架,构建了XylR-Pu基因线路,并以绿色荧光蛋白GFP为报告分子,GFP的荧光值可以指征结合诱导剂后的XylR蛋白对Pu启动子的诱导强度,并在基因线路中加入四串联终止序列来降低背景值。最后对XylR蛋白的信号识别区进行连续易错PCR,构建随机突变体文库,从中筛选具有更高感应强度、更好灵敏度及特异性的调控蛋白。结果:四串联终止序列可有效降低XylR-Pu通路的背景值,随机突变体文库中筛选出的生物元件eX0-4,对TNT表现出良好的感应强度、灵敏度及特异性。结论:XylR蛋白在大肠杆菌中对硝基甲苯响应不明显,但筛选得到的突变蛋白eX0-4,为后续生物传感器的更深层次地开发提供了优良的元件储备。另外,利用易错PCR构建随机突变体文库从中筛选发挥预定功能的突变蛋白质也可成为挖掘生物元件的一种通用方法。     

Influence of PAHs in ambient air on chromosomal aberrations in exposed subjects: international study - EXPAH

The aim of this study was to determine the influence of carcinogenic polycyclic aromatic hydrocarbons (c–PAHs) in complex mixtures in ambient air on DNA damage (chromosomal aberrations) in occupationally exposed subjects measured as percent of aberrant cells (% AB.C.).

There were in total 203 exposed subjects and 150 respective controls in the whole project, allocated in three different European cities – Kosice (Slovakia), Prague (Czech Republic) and Sofia (Bulgaria). The studied population from Kosice (Slovakia) consisted of 106 subjects. From these 51 were exposed policemen and 55 were controls. The Czech population comprised 52 exposed policemen and 50 controls. In Bulgaria, there were two equally numerous exposed groups: 50 policemen and 50 professional bus drivers together with 45 controls. According to personal monitoring, policemen and bus drivers in the Bulgarian capital Sofia were exposed to the highest levels of c-PAHs amongst the exposed subject groups in the cities (45.3 ± 25.9 ng/m³ in policemen resp. 36.1 ± 31.6 ng/m³ in bus drivers in Sofia, 26.8 ± 39.8 ng/m³ for policemen in Kosice and 11.9 ± 11.2 ng/m³ for policemen in Prague), compared to the respective controls (24.9 ± 17.7 ng/m³ for controls in Sofia, 7.9 ± 3.8 ng/m³ for controls in Kosice and 6.2 ± 3.6 ng/m³ for controls in Prague).

We observed the following frequency of % AB.C. scored by conventional method: 2.60 ± 2.64 in exposed policemen and 2.14 ± 1.61 in controls in Kosice (p = n.s.); 2.33 ± 1.53 in exposed policemen and 1.94 ± 1.28 in controls in Prague (p = n.s.); 3.04 ± 1.64 in exposed policemen, respectively, 3.60 ± 1.63 in exposed bus drivers and 1.79 ± 0.77 in the control group in Sofia (p < 0.05, respectively, p < 0.05).

According to data from multiple regression analysis, and group comparison of smokers versus nonsmokers in Sofia also cigarette smoking (p = 0.055) and the age (p = 0.020) seem to play an important role within the aberrant cell formation in addition to the occupational c-PAHs exposure (p = 0.000). Smoking status was the modifying factor for % AB.C. in Kosice (p = 0.020) after multiple regression approach was employed.

In summary, we can say that subjects occupationally exposed to higher levels of c-PAHs in ambient air in Sofia are at greater genotoxic risk compared to those working indoors.     

三硝基甲苯致白内障机理及其在晶状体内代谢的研究

在建立TNT大鼠白内障的基础上,用HPLC分析了晶状体内TNT及其代谢产物,并用ESR及NBT方法检测了TNT在晶状体内的代谢过程所产生的自由基。结果表明,慢性染毒24个月的大鼠白内障晶状体内含有TNT原形和4氨基2,6二硝基甲苯代谢产物,以及在体外与正常晶状体微粒体孵育可产生TNT硝基阴离子自由基和超氧阴离子自由基。上述结果提示,TNT可进入晶状体内,在其还原代谢过程中产生硝基阴离子自由基中间产物,在有氧条件下进而产生超氧阴离子自由基,这可能是TNT导致白内障的启动因素。     

Reduction in denitrification activity in field soils exposed to long term contamination by 2,4,6-trinitrotoluene (TNT)

Terrestrial sites contaminated with 2,4,6-trinitrotoluene (TNT) are a widespread and persistent problem and often contain non-vegetated areas with TNT concentrations well in excess of 1000 mg kg(-1). In this study, we examined the effect of TNT on denitrification activity in field soils, and compared the sensitivity of denitrifying enzymes to TNT. DNA probes assessed the prevalence of nirS, nirK and nosZ (encoding cd(1) or copper nitrite reductase and nitrous oxide reductase, respectively), denitrifying genotypes in the culturable and total microbial community. The nitrate (NaR), nitrite (NiR) and nitrous oxide (N(2)OR) reductase activities in field soil and in isolates were assessed by gas chromatography. The relative occurrence of the nirK, nirS or nosZ genotypes increased in the cultured community and in total uncultured community DNA as nitroaromatic concentrations increased. However, denitrifying activity decreased in response to increasing TNT concentrations, with an IC(50) for NaR+NiR+nitric oxide reductase (NOR) of 400 mg TNT kg(-1) soil and for N(2)OR of 26 mg TNT kg(-1) soil. The denitrifying activity of four soil isolates also decreased in response to TNT, with N(2)OR activity being three times more sensitive to TNT than NaR+NiR+NOR activity. Interestingly, there were 118 times more nirK isolates than nirS isolates in uncontaminated soil but only 1.5 times more in soil containing 17400 mg kg(-1) TNT. The results from this study indicated that TNT reduced denitrification activity in field soils, and N(2)OR was much more sensitive to TNT than NaR+NiR+NOR.     

Determination of isocyanate biomarkers in construction site workers

4,4′-Methylenediphenyl diisocyanate (MDI) is the most important isocyanate in the manufacture of polyurethanes, dyes, pigments and adhesives. High concentrations of isocyanates are a potent respiratory irritant. Therefore, it is important to develop methods to monitor exposure to such compounds. We monitored biological samples from 40 non-exposed and 45 exposed construction site workers. 4,4′-Methylenedianiline (MDA) and N-acetyl-4,4′-MDA (AcMDA) were determined from untreated urine (U-MDA, U-AcMDA) and MDA was analysed from acid-treated urine (U-MDA-tot). Haemoglobin (Hb) adducts of MDA (Hb-MDA) were determined in all workers. The levels of biomarkers decreased in the following order: U-MDA-tot>U-AcMDA>U-MDA>Hb-MDA. The same order was found for the percentage of samples, which were found positive in exposed workers: 100%, 91%, 91%, 27%. The urine levels U-MDA-tot correlate with U-MDA, U-AcMDA and Hb-MDA with r=0.79, 0.86 and 0.39, respectively (Spearman rank order, p<0.01). U-AcMDA correlates with U-MDA and Hb-MDA with r=0.77 and 0.47, respectively (p<0.01). U-MDA correlates with Hb-MDA (r=0.38, p<0.05). The levels in the controls were significantly lower than in the exposed workers for all compounds (Mann–Whitney test, p<0.01). The median isocyanate-specific IgE-level was higher in the exposed workers, but the difference was statistically not significant. The change of the biomarker levels was compared in a group of workers (n=20), which were analysed prior to isocyanate exposure and after the exposure for ～4–7 months. All urine MDA metabolites and the Hb-adduct levels increased significantly (Wilcoxon sign test, p<0.01). Total IgE increased significantly after the exposure with isocyanate activity (p<0.01). With the present work it could be shown that outdoor workers are exposed to a similar extent as workers from a MDI factory.     

Role of bacterial nitroreductase and O-acetyltransferase in urine mutagenicity assay of rats exposed to 2,4,6-trinitrotoluene (TNT)

The urine mutagenicity of rats exposed to 2,4,6-trinitrotoluene (TNT) by i.p. injection was studied in the Salmonella assay using indicator strains with various levels of 'classical' nitroreductase or acetyl-CoA:N-hydroxylarylamine O-acetyltransferase activity. The strains used were the conventional Salmonella typhimurium TA98, nitroreductase-deficient TA98NR and -overproducing YG1021, and O-acetyltransferase-deficient TA98/1,8-DNP6 and -overproducing YG1024. TA98, YG1021 and YG1024 clearly detected the increase of direct urine mutagenicity. A slight increase of mutagenicity was also detected with metabolic activation in YG1021 and YG1024. High levels of both nitroreductase and O-acetyltransferase significantly increased the sensitivity of the indicator strain to the mutagenicity of urine caused by TNT exposure, while the nitroreductase- or O-acetyltransferase-deficient strains gave negative responses.