Assessment of environmental hazards of 1,3,5-trinitrobenzene

Trends in environmental monitoring of high explosives present in soil/sediment/groundwater using LC-MS/MS

Environmental contamination by explosives occurs due to improper handling and disposal procedures. Explosives and their transformation products pose threat to human health and the ecosystem. Trace level detection of explosives present in different environmental matrices is a challenge, due to the interference caused by matrix components and the presence of cocontaminants. Liquid chromatography combined with tandem mass spectrometry (LC-MS/MS) is an advanced analytical tool, which is ideal for quantitative and qualitative detection of explosives and its metabolites at trace levels. This review aims to showcase the current trends in the application of LC-MS/MS for detecting explosives present in soil, sediment, and groundwater with detection limits ranging from nano to femtogram levels. Specificity and advantages of using LC-MS/MS over conventional analytical methods and various processing methods and techniques used for sample preparation are discussed in this article. Important application aspects of LC-MS/MS on environmental monitoring include site characterization and degradation evaluation. Studies on qualitative and quantitative LC-MS/MS analysis in determining the efficiency of treatment processes and contamination mapping, optimized conditions of LC and MS/MS adopted, role of different ionization techniques and mass analyzers in detection of explosives and its metabolites, relative abundance of various product ions formed on dissociation and the levels of detection achieved are reviewed. Ionization suppression, matrix effect, additive selection are some of the major factors which influence MS/MS detection. A summary of challenges and future research insights for effective utilization of this technique in the environmental monitoring of explosives are presented.

Dumped munitions: New insights into the metabolization of 2,4,6-trinitrotoluene in Baltic flatfish

Livers from dab (Limanda limanda), plaice (Pleuronectes platessa) and flounder (Platichthys flesus) sampled from the Baltic Sea were used to determine the interaction of flatfish CYP1A enzymes with 2,4,6-trinitrotoluene (TNT) in vitro. Competitive inhibition of 7-ethoxyresorufin-O-deethylase (EROD) and 7-methoxyresorufin-O-deethylase (MROD) could be demonstrated for all three flatfish species. The highest inhibition of CYP1A activities was measured in liver samples of flounder resulting in a half maximal inhibitory concentration (IC₅₀) of 28.1 μM TNT. Due to their lower inhibition (EROD IC₅₀ 65.2 μM TNT, MROD IC₅₀ 40.3 μM TNT), dab liver samples were used to conduct in vitro metabolization experiments with TNT. The metabolization of TNT in fish was investigated with post-mitochondrial fractions (PMF) of dab liver as a model system after adding different cofactors. Rapid and time-dependent enzymatic degradation of TNT was observed. The concentrations of 4-amino-2,6-dinitrotoluene and 2-amino-4,6-dinitrotoluene increased in the samples over time. Additionally, 2,2,6,6-tetranitro-4,4-azoxytoluene was detected in one sample. The results of this study indicate that in vitro experiments are useful to investigate the xenobiotic metabolism of fish under controlled conditions prior to field studies. The metabolites found can serve as target compounds for marine monitoring of TNT contamination in munition dumpsites.

Toxicokinetics and tolerance of a high energy material 3,4,5-trinitropyrazole (TNP) in mice

The high-energy compound 3,4,5-trinitropyrazole (TNP) was developed as an alternative to other less energetic and more sensitive explosive materials, in particular 1-methyl-2,4,6-trinitrobenzene (TNT). However, the level of toxicity of TNP remains understudied. Here using an in vivo CD1 mouse model, we mimicked an acute exposure (24 h) to TNP, given either orally or intravenously, and determined the maximum administrable doses (190 mg/kg and 11 mg/kg, respectively), as well as the lethal dose for 50% (LD₅₀) of female or male mice (390 mg/kg for both) treated intravenously with TNP alone. Several metabolites including nitroso-dinitro-pyrazole, hydroxylamino-dinitro-pyrazole, hydroxyl-dinitro-pyrazole and amino-dinitro-pyrazole were identified in urine. TNP is quickly metabolized and eliminated via urine as two main amino-dinitro-pyrazole metabolites. A comparison of the transcriptomic effects of TNP and TNT after 10 days exposure enabled us to demonstrate no major induction of transcripts involved both in cell death mechanisms (apoptosis, necrosis, autophagy) and physiological pathways (glycolysis, ATP production). Finally, subchronic exposure to TNP was replicated in female mice, fed 16.8-52.8 mg/kg/day of TNP for one month, to study the impact on cellular functions. Although blood TNP levels remained high, a lower rate of TNP accumulation in the liver and lungs were observed than during an acute exposure. Conversely, cellular stress functions explored using the RT² Profiler™ PCR Array Mouse Molecular Toxicology PathwayFinder remained unaltered after this chronic exposure. These findings demonstrate that TNP can be rapidly eliminated in vivo without accumulating in vital organs.

The para isomer of dinitrobenzene disrupts redox homeostasis in liver and kidney of male wistar rats

Background

Para-Dinitrobenzene (p-DNB) is one of the isomers of dinitrobenzene which have been detected as environmental toxicants. Skin irritation and organ toxicities are likely for industrial workers exposed to p-DNB. This study evaluated the effect of sub-chronic exposure of rats to p-DNB on cellular redox balance, hepatic and renal integrity.

Methods

Forty eight male Wistar rats weighing 160–180 g were administered 50, 75, 1000 and 2000 mg/kg b.wt (body weight) of p-DNB or an equivalent volume of vehicle (control) orally and topically for 14 days. After the period of treatment, the activities of kidney and liver catalase (CAT), alkaline phosphatase (ALP) and superoxide dismutase (SOD) as well as extent of renal and hepatic lipid peroxidation (LPO) were determined. Serum ALP activity and plasma urea concentration were also evaluated.

Results

Compared with control animals, p-DNB -administered rats showed decrease in the body and relative kidney and liver weights as well as increased renal and hepatic hydrogen peroxide and lipid peroxidation levels accompanied by decreased superoxide dismutase and catalase activities. However, p-DNB caused a significant increase in plasma urea concentration and serum, liver and kidney ALP activities relative to control. In addition, p-DNB caused periportal infiltration, severe macro vesicular steatosis and hepatic necrosis in the liver.

Conclusions

Our findings show that sub-chronic oral and sub-dermal administration of p-DNB may produce hepato-nephrotoxicity through oxidative stress.

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Activities of kidney and liver catalase and superoxide dismutase were decreased by p-DNB.

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p-DNB increased serum, liver and kidney activity of alkaline phosphatase.

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Plasma urea concentration was increased by p-DNB.

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Lipid peroxidation and H₂O₂ level were increased by p-DNB.

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p-DNB caused histopathological changes in liver and kidney tissues.

Construction of 2,4,6-Trinitrotoluene Biosensors with Novel Sensing Elements from Escherichia coli K-12 MG1655

Detection of 2,4,6-trinitrotoluene (TNT) has been extensively studied since it is a common explosive filling for landmines, posing significant threats to the environment and human safety. The rapid advances in synthetic biology give new hope to detect such toxic and hazardous compounds in a more sensitive and safe way. Biosensor construction anticipates finding sensing elements able to detect TNT. As TNT can induce some physiological responses in E. coli, it may be useful to define the sensing elements from E. coli to detect TNT. An E. coli MG1655 genomic promoter library containing nearly 5,400 elements was constructed. Five elements, yadG, yqgC, aspC, recE, and topA, displayed high sensing specificity to TNT and its indicator compounds 1,3-DNB and 2,4-DNT. Based on this, a whole cell biosensor was constructed using E. coli, in which green fluorescent protein was positioned downstream of the five sensing elements via genetic fusion. The threshold value, detection time, EC200 value, and other aspects of five sensing elements were determined and the minimum responding concentration to TNT was 4.75 mg/L. According to the synthetic biology, the five sensing elements enriched the reservoir of TNT-sensing elements, and provided a more applicable toolkit to be applied in genetic routes and live systems of biosensors in future.

In Vitro Inhibition of Mammalian Glutathione Transferases by Selected Nitrobenzenes

Five structurally related nitrobenzenes (1,2-dinitrobenzene, 1,3-dinitrobenzene, 1,4-dinitrobenzene, 1,3,5-trinitrobenzene, and picric acid) and Meisenheimer complex [1-(S-glutathionyl)-2,4,6-trinitrocyclohexadienate] were evaluated as possible inhibitors of affinity purified mammalian glutathione transferases (GSTs) isolated from human liver or human term placenta and rat fiver. The results suggest that the degree of GST inhibition depends upon both the chemical in question and the enzyme source. Among the nitrobenzenes tested, 1,3,5-trinitrobenzene (TNB) was found to be the most potent inhibitor of GST activity toward 1-chloro-2,4-dinitrobenzene (CDNB) from all the sources, whereas 1,3-dinitrobenzene (1,3-DNB) was the least effective. TNB-caused inhibition of GST activity toward CDNB appeared to be isozyme specific in that compared to the enzyme from human term placenta (GSTP1–1), the degree of inhibition of the mixture of GST isozymes present in the fivers of adult rats and humans was low. The enzyme assays conducted with 3,4-dichloro-1-nitrobenzene (DCNB), ethacrynic acid (EA), and 4-nitropyridinei N-oxide also suggested the isozymespecific inhibition of rat fiver GST activity by TNB. The nature of TNB-caused inhibition of GSTP1–1 was competitive with respect to CDNB and yielded a Ki value of 12.5 θ M. With EA, a specific substrate for GSTP1–1, an IC50 value of ∼ 16 θ M was estimated for the GSTP1–1 inhibition by TNB. The Meisenheimer complex, the product of nonenzymatic GSH conjugation with TNB by different GSTs, was found to be the most potent inhibitor of mammalian GSTs, and IC50 values ranged between 1 and 4 θ M when the enzyme activity was assayedusing CDNB. The nature of GSTP1–1 inhibition was noncompetitive with respect to CDNB, with a Ki value of 1 θ M for Meisenheimer complex. Although a precise mechanism was not identified, it is postulated that GSH depletion and/or GST inhibition may contribute, at least partly, to the target organ toxicity caused by exposures of animals to different nitrobenzenes reported in the literature.

Selective and sensitive TNT sensors using biomimetic polydiacetylene-coated CNT-FETs

Miniaturized smart sensors that can perform sensitive and selective real-time monitoring of target analytes are tremendously valuable for various sensing applications. We developed selective nanocoatings by combining trinitrotoluene (TNT) receptors bound to conjugated polydiacetylene (PDA) polymers with single-walled carbon nanotube field-effect transistors (SWNT-FET). Selective binding events between the TNT molecules and phage display derived TNT receptors were effectively transduced to sensitive SWNT-FET conductance sensors through the PDA coating layers. The resulting sensors exhibited an unprecedented 1 fM sensitivity toward TNT in real time, with excellent selectivity over various similar aromatic compounds. Our biomimetic receptor coating approach may be useful for the development of sensitive and selective micro- and nanoelectronic sensor devices for various other target analytes.

Toxicity of trinitrotoluene to sheepshead minnows in water exposures

Lethal effects of trinitrotoluene (TNT) to juvenile sheepshead minnows (JSHM) (Cyprinodon variegatus) were assessed in ten-day water exposures. Ten-day median lethal concentrations (LC50s) were 2.3 and 2.5 mg L(-1), the 10-d median lethal residue value (LR50) was 26.1 micromol kg(-1) wet weight (ww), and bioconcentration factors (BCFs) ranged from 0.7 to 2.4 L kg(-1). The lethal effects of TNT and its transformation products 2-aminodinitrotoluene (2-ADNT), 2,4-diaminonitrotoluene (2,4-DANT) and trinitrobenzene (TNB) to JSHM were compared in 5-d static-renewal exposures. Nitroreduction decreased the toxicity of TNT to SHM, as the 5-d LC50 for 2-ADNT was 8.6 mg L(-1) and the lowest lethal concentration of 2,4-DANT was 50.3 mg L(-1). TNB (5-d LC50=1.2 mg L(-1)) was more toxic than TNT to SHM. The 5-d LR50s were 4.3 mg kg(-1)ww (20.4 micromol kg(-1)) for SumTNT (TNT exposure) and 54.2 mg kg(-1)ww (275.3 micromol kg(-1)) for 2-ADNT and significant mortality occurred at 47.4 mg kg(-1)ww (283.6 micromol kg(-1)). The range of BCF values was from 1.8 to 2.4, 5.6 to 8.0, and 0.6 to 0.9Lkg(-1) for TNT, 2-ADNT, and 2,4-DANT, respectively.

Neue Trinkwasser-Leitwerte für monocyclische Nitroverbindungen

Nitro compounds are important industrial chemicals with a broad range of applications. During their commercial production or practical use and through leaching from military waste sites they may be released into the environment and thus lead to a contamination of drinking water resources. In the last 15-20 years, the wider public first became aware of nitro compounds as contaminants in groundwater and drinking water resources that originated from manufacturing and processing of secondary explosives during World War II. In 1980, the former Bundesgesundheitsamt (BGA; Federal Health Office) had based its first risk assessment of monocyclic nitro compounds in drinking water on the known carcinogenicity of some aromatic amines in the working environment. On this basis, the BGA recommended for metabolites of aromatic nitro compounds a guide value of 0.1 mug/l for the sum of aromatic amines. From the beginning to the middle of the 1990s, the BGA established a more specific health-related assessment for the individual compounds, but not on the basis of tolerable or acceptable body doses but of dimensionless risk assessment scores ranking their combined toxic and carcinogenic potential on a scale from 1 to 100. In this contribution, we derived new health-based drinking water guide values for 19 nitro(aromatic) compounds and nitramines, including hexogen, octogen, and tetryl as well as the O-nitro compound PETN. All compounds under consideration have been detected within the last 15 years in Germany at contaminated sites close to or directly in groundwater resources for drinking water. For toxicological evaluation and derivation of guideline values for the nitro compounds of interest, the tolerable daily intake (TDI) approach was used for chemicals exhibiting a threshold for toxic effects. This was done by using established tolerable body doses for humans based on an identified NOAEL/LOAEL for the most sensitive toxic endpoint. In the case of non-threshold chemical substances, suitable estimates of excess lifetime cancer risk have been applied.

Toxicological guidelines for monocyclic nitro-, amino- and aminonitroaromatics, nitramines, and nitrate esters in drinking water

In order to secure a safe drinking water supply, the setting of tolerable/acceptable ceilings of drinking water hygiene is required with regard to xenobiotics resulting from several anthropogenic impacts. This is done in practice by using drinking water guidelines or standards as quantitative objectives. The list of the new EU Directive or the German drinking-water standards is limited to those parameters that have the highest relevance for drinking water quality; nitro compounds (NCs) are not regulated. Because other substances contained in water can also represent a hazard for human health, the German Drinking Water Ordinance clarifies that specific actions must be implemented if compounds other than those regulated appear at concentrations that may be a cause for concern regarding human health. NCs serve as intermediates for dyes, pharmaceuticals, and synthetic materials; they themselves are used as solvents, explosives, and pesticides. During their commercial production or from their use, they may be released to the environment and lead to a contamination of aquatic systems and thus also of drinking water resources. In practice, therefore, a need for assessment is frequently given for relevant NCs. For 19 nitro-, amino-, and aminonitroaromatics, nitramines, and nitrate esters health-based drinking water guide values have been derived. For toxicological evaluation and derivation of guideline values for the NCs of interest, the tolerable daily intake approach was used for chemicals exhibiting a threshold for toxic effects. This was done by using established tolerable body doses for humans based on an identified no-observed-adverse-effect level/low-observed-effect-level for the most sensitive indicator for toxicity. In the case of nonthreshold chemical substances, suitable estimates of excess lifetime cancer risk have been applied.

Use of a Salmonella microsuspension bioassay to detect the mutagenicity of munitions compounds at low concentrations

Past production and handling of munitions has resulted in soil contamination at various military facilities. Depending on the concentrations present, these soils pose both a reactivity and toxicity hazard and the potential for groundwater contamination. Many munitions-related chemicals have been examined for mutagenicity in the Ames test, but because the metabolites may be present in low environmental concentrations, a more sensitive method is needed to elucidate the associated mutagenicity. RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine), TNT (2,4,6-trinitrotoluene), tetryl (N-methyl-N-2,4,6-tetranitroaniline), TNB (1,3,5-trinitrobenzene) and metabolites were examined for mutagenicity in a microsuspension modification of the Salmonella histidine reversion assay with and without metabolic activation. TNB and tetryl were positive in TA98 (32.5, 5.2revertants/nmole) and TA100 (7.4, 9.5revertants/nmole) without metabolic activation and were more potent than TNT (TA98, 0.3revertants/nmole; TA100, 2.4revertants/nmole). With the exception of the tetranitroazoxytoluene derivatives, TNT metabolites were less mutagenic than TNT. RDX and two metabolites were negative in both strains, however, hexahydro-1,3,5-trinitroso-1,3,5-triazine was positive in TA100 with and without S9. Microsuspension bioassay results tend to correlate well with published Ames test data, however, there are discrepancies among the published data sets and the microsuspension assay results.

Application of solvent microextraction to the analysis of nitroaromatic explosives in water samples

The application of solvent microextraction to the analysis of nitroaromatic explosives is presented. Extraction of 11 nitroaromatics was achieved by suspending 1 microl of organic solvent to the tip of a microsyringe in a stirred aqueous solution. Parameters such as extraction solvent, stirring rate, salt concentration and sampling time were studied and optimized. The limits of detection using bench-top quadrupole mass spectrometry and short extraction times (15 min) were found to be between 0.08 and 1.3 microg/l and the relative standard deviations ranged between 4.3 and 9.8%. Although precision and accuracy of quantification of the method are still needed, solvent microextraction proved to be a fast, simple and inexpensive tool for preconcentration and matrix isolation of nitroaromatics on a microscale.

Cytotoxic and genotoxic effects of energetic compounds on bacterial and mammalian cells in vitro

The mutagenicity and toxicity of energetic compounds such as 2,4, 6-trinitrotoluene (TNT), 1,3,5-trinitrobenzene (TNB), hexahydro-1,3, 5-trinitro-1,3,5-triazine (RDX) and octahydro-1,3,5,7-tetranitro-1,3, 5,7-tetrazocine (HMX), and of amino/nitro derivatives of toluene were investigated in vitro. Mutagenicity was evaluated with the Salmonella fluctuation test (FT) and the V79 Chinese hamster lung cell mutagenicity assay. Cytotoxicity was evaluated using V79 and TK6 human lymphoblastic cells. For the TK6 and V79 assays, TNB and 2, 4,6-triaminotoluene were more toxic than TNT, whereas RDX and HMX were without effect at their maximal aqueous solubility limits. The primary TNT metabolites (2-amino-4,6-dinitrotoluene, 4-amino-2, 6-dinitrotoluene, 2,4-diamino-6-nitrotoluene and 2, 6-diamino-4-nitrotoluene) were generally less cytotoxic than the parent compound. The FT results indicated that TNB, TNT and all the tested primary TNT metabolites were mutagenic. Except for the cases of 4-amino-2,6-dinitrotoluene and 2,4-diamino-6-nitrotoluene in the TA98 strain, addition of rat liver S9 resulted in either no effect, or decreased activity. None of the tested compounds were mutagenic for the V79 mammalian cells with or without S9 metabolic activation. Thus, the FT assay was more sensitive to the genotoxic effects of energetic compounds than was the V79 test, suggesting that the FT might be a better screening tool for the presence of these explosives. The lack of mutagenicity of pure substances for V79 cells under the conditions used in this study does not preclude that genotoxicity could actually exist in other mammalian cells. In view of earlier reports and this study, mutagenicity testing of environmental samples should be considered as part of the hazard assessment of sites contaminated by TNT and related products.

Nitroaromatic munition compounds: environmental effects and screening values

Available data on the occurrence, transport, transformation, and toxicity of eight nitroaromatic munition compounds and their degradation products, TNT, TNB, DNB, DNA, 2-ADNT, RDX, HMX, and tetryl were used to identify potential fate in the environment and to calculate screening benchmarks or safe environmental levels for aquatic and terrestrial organisms. Results of monitoring studies revealed that some of these compounds persist at sites where they were produced or processed. Most of the compounds are present in soil, sediment, and surface water or groundwater at military sites. Soil adsorption coefficients indicate that these chemicals are only moderately adsorbed to soil and may leach to groundwater. Most of these compounds are transformed by abiotic or biotic mechanisms in environmental media. Primary transformation mechanisms involve photolysis (TNT, RDX, HMX, tetryl), hydrolysis (tetryl), and microbial degradation (TNT, TNB, DNB, DNA, 2-ADNT, and HMX). Microbial degradation for both nitro and nitramine aromatic compounds involves rapid reduction of nitro groups to amino groups, but further metabolism is slow. With the exception of DNB, complete mineralization did not usually occur under the conditions of the studies. RDX was resistant to microbial degradation. Available ecotoxicological data on acute and chronic studies with freshwater fish and invertebrates were summarized, and water quality criteria or ecotoxicological screening benchmarks were developed. Depending on the available data, criteria/benchmarks were calculated according to USEPA Tier I or Tier II guidelines. The munitions chemicals are moderately to highly toxic to freshwater organisms, with chronic screening values < 1 mg/L. For some chemicals, these low values are caused by inherent toxicity; in other cases, they result from the conservative methods used in the absence of data. For nonionic organic munitions chemicals, sediment quality benchmarks were calculated (based on Kow values and the final chronic value) according to USEPA guidelines. Available data indicate that none of the compounds is expected to bioconcentrate. In the same manner in which reference doses for humans are based on studies with laboratory animals, reference doses or screening benchmarks for wildlife may also be calculated by extrapolation among mammalian species. Chronic NOAELs for the compounds of interest were determined from available laboratory studies. Endpoints selected for wildlife species were those that diminish population growth or survival. Equivalent NOAELs for wildlife were calculated by scaling the test data on the basis of differences in body weight. Data on food and water intake for seven selected wildlife species--short-tailed shrew, white-footed mouse, meadow vole, cottontail rabbit, mink, red fox, and whitetail deer--were used to calculate NOAELs for oral intake. In the case of TNB, a comparison of toxicity data from studies conducted with both the white-footed mouse and the laboratory rat indicates that the white-footed mouse may be more resistant to the toxic effects of chemicals than the laboratory rat and may further indicate the lesser sensitivity of wildlife species to chemical insult. Chronic NOAEL values for the test species based on the laboratory studies indicate that, by the oral route of exposure, TNB and RDX are not highly toxic to mammalian species. However, as seen with TNB, values are less conservative when chronic studies are available or when studies were conducted with wildlife species. Insufficient data were located to calculate NOAELs for avian species. In the absence of criteria or guidelines for terrestrial plants, invertebrates, and soil heterotrophic processes, LOECs were used as screening benchmarks for effect levels in the environment. In most cases, too few data were available to derive a screening benchmark or to have a high degree of confidence in the benchmarks that were derived. (ABSTRACT TRUNCATED)