Release of carcinogenic hydrocarbons in the carbonization of coal pitch

The carbonization of industrial coal-pitch samples is studied, with particular attention to the liberation and conversion of benz[a]pyrene and other carcinogenic polycyclic aromatic hydrocarbons. The hydrocarbon composition of pitch sublimates and the benz[a]pyrene concentration in the smokestack gases are determined during regular and high-speed carbonization. The maximum benz[a]pyrene content in the smokestack gases is seen at 750–800°C, regardless of its content in the initial pitch. The benz[a]pyrene content basically determines the carcinogenic hazards of pitch processing.     

Reducing the carcinogenic impact of pitch processing

Diverse opinions exist regarding the properties of benz[a]pyrene and other polycyclic aromatic hydrocarbons in coal pitch and their carcinogenic impact. Current concepts regarding chemical carcinogenesis and the development of occupational sickness are outlined. Information is presented relating to the reduction in the carcinogenic impact of coal pitch and its processing products. It is shown that the content of benz[a]pyrene and other polycyclic aromatic hydrocarbons in coal pitch, its sublimates, and atmospheric emissions may be reduced by means of various additives. However, it is probably impossible to eliminate benz[a]pyrene emission completely, since it is an unavoidable product of the high-temperature pyrolysis of organic materials.     

Carbonization of coal pitch with reduced carcinogenic hydrocarbon emissions

The carbonization of coal pitch in the presence of an additive (5?C14%) that contains sulfone groups is considered. The quantity of pitch sublimates is reduced, along with their content of carcinogenic polycyclic aromatic hydrocarbons. In terms of benz[a]pyrene, the reduction in carcinogenic effect is 300% or more. The benz[a]pyrene content in the waste gas is studied throughout the carbonization process: it is a maximum at 750?C800°C, on account of its high-temperature synthesis in the gas phase.     

Emission of carcinogenic polyaromatic hydrocarbons in the carbonization of coal pitch

The composition of polyaromatic hydrocarbons liberated at different carbonization rates of coal pitch in an inert atmosphere is studied. The benz[a]pyrene equivalent is calculated. It is shown that reducing the carbonization rate increases the emissions of carcinogenic polyaromatic hydrocarbons.     

Assessing the carcinogenicity of carbon-bearing binders

Methods of determining the carcinogenicity of carbon-bearing binders in terms of their benzo[a]pyrene content and the benzo[a]pyrene emissions in binder carbonization at temperatures up to 850°C are considered. In the laboratory, CARBORES-T and CARBORES-P binders with reduced benzo[a]pyrene content are studied, as well as the industrial carbon pitch from which they are derived. It is found that predicting the carcinogenicity of carbon-bearing binders in terms of their benzo[a]pyrene content is unsatisfactory, largely because the formation and emission of benzo[a]pyrene on binder heating is ignored. Quantitative determination of the benzo[a]pyrene emission in the carbonization of the binders may be regarded as a more reliable and more universal method. It may be used to compare the carcinogenicity of products derived from coal and petroleum, as well as binders that do not contain benzo[a]pyrene.     

Polycyclic aromatic hydrocarbons in coke-plant wastewater

The content of polycyclic aromatic compounds—including the strong carcinogens benz[a]pyrene and dibenz[a,h]anthracene—in coke-plant wastewater is investigated. Biochemical purification permits the removal of the following polycyclic aromatic compounds: naphthalene, acenaphthylene, fluorene, acenaphthene, phenanthrene, anthracene, fluoranthene, pyrene, and benz[k]fluoranthene (79.6–99.9% removal); and benz[a]pyrene (65.7% removal). By contrast, biochemical treatment increases the content of the following compounds in the wastewater: benz[b]fluoranthene, benz[g,h,i]perylene, and indeno[1,2,3-cd]pyrene.     

Influence of the coke filler on the carcinogenicity of pitch–coke mixtures on carbonization

The emissions of benzo[a]pyrene at different temperatures and its concentration in the exhaust gases are measured in laboratory experiments on the carbonization (at temperatures up to 850°C) of coalpitch and petroleum-pitch binders and their mixtures with roasted petroleum and pitch coke. These pitch–coke mixtures are similar in composition to the anode mass used in aluminum production. The experiments confirm that the total benzo[a]pyrene emissions are much greater in the carbonization of petroleum pitch produced by cracking (T _so = 100°C) than for electrode pitch (T _so = 89°C) and other coal pitch. In most experiments, the benzo[a]pyrene emissions in the carbonization of pitch–coke mixtures is markedly less than for individual binder pitches. It is found that the benzo[a]pyrene emissions in the carbonization of a mixture based on pitch coke are much less than for a mixture based on petroleum coke in the high-temperature region that presents the greatest environmental hazard.     

Environmental impact of polymer-waste disposal

The laboratory carbonization of well-known polymers to 850°C is studied, in order to determine the benzo[a]pyrene emissions. In carbonization, the exhaust gases from all the polymers contain benzo[a]pyrene in levels far exceeding workplace air standards. The levels are higher for carbon-chain polymers than for heterochain polymers. The utilization of polymer wastes with the coal batch in coke ovens is investigated. It is found that the yield of gas and its content of benzo[a]pyrene are several times higher than for industrial coke ovens. This means that, in the industrial coking of coal batch with added carbon-chain polymers, elevated expansion pressure should be expected in the coke oven, along with increased atmospheric emissions of benzo[a]pyrene.     

Characterization of molecular markers in smoke from residential coal combustion in China

The organic constituents and distributions of molecular markers emitted from a residential coal-stove burning honeycomb coal briquettes were determined in this study. The major organic components emitted directly in smoke particles were polycyclic aromatic hydrocarbons (PAHs), with abundant hydroxy-polycyclic aromatic hydrocarbons (OH-PAHs), i.e., thermally altered derivative compounds from coal combustion, UCM (unresolved complex mixture of branched and cyclic compounds), n-alkanes and n-alkanoic acids. Other compounds present as minor components included n-alkenes, phenols, alkylbenzenes and n-alkanols. The distributions of the organic compounds in the coal smoke samples were highly variable and dependent on combustion temperature, flame aeration, fire duration, and coal rank. Coal smoke emissions may be identified by some indicators including: (1) presence of hydroxy-PAHs, (2) the decrease in carbon preference index (CPI) of n-alkanoic acids with increasing rank, (3) the decrease of the ratios of 17α(H),21β(H)-29-norhopane to 22R-17α(H),21β(H)-homohopane and 17α(H),21β(H)-29-norhopane to 17α(H),21β(H)-hopane with increasing rank, (4) the increases in the homohopane index [22S/(22S + 22R)] and the 17α(H),21β(H)-hopane to 17β(H), 21α(H)-hopane ratio with increasing rank, and (5) the increase of benzo[e]pyrene/(benzo[e]pyrene + benzo[a]pyrene) with increasing rank. In addition, the diagnostic ratios among PAHs and between PAHs and the corresponding hydroxy-PAHs, such as benz[a]anthracene/(benz[a]anthracene + chrysene), indeno[1,2,3-cd]pyrene/(indeno[1,2,3-cd]pyrene + benzo[ghi]perylene), pyrene/OH-pyrene, and chrysene/OH-chrysene can be used to distinguish bituminous from anthracite coal smoke emissions.     

Production of coal tar/petroleum pitch by the combined distillation of coal tar and heavy cycle oil at JSC Gubakhinskii Koks

Coal tar/petroleum pitch has been produced by the combined distillation of coal tar and heavy cycle oil from catalytic cracking, in industrial trials. In processing a 60: 40 mixture of those components, 306 t of pitch that meets the requirements for anode binder is produced. The benzo[a]pyrene content is lower in the petroleum–coal pitch than in regular coal pitch used in electrode production.     

PAH Metabolism in Cultured Mammalian Lung Epithelial Cells

In vitro cultures of mammalian cells have an advantage over animal experiments in that human cells can be directly compared with various other mammalian cells. In this study we compared the metabolism of several polycyclic aromatic hydrocarbons (PAH) (benzo[a]pyrene, chrysene, pyrene, phenanthrene, benz[a]anthracene) in epithelial cells from hamster, rat and human lung.

The cells investigated in our system yielded more or less qualitatively similar metabolic profiles for all PAH mentioned above except benz[a]anthracene in the three species. Additionally, species-specific differences were prominent between human and rodent cells with regard to the ratio of phase I and phase II metabolites.

Indications have been obtained that monooxygenase induction is required in fetal cells prior to metabolic conversion of those PAH which lack an inductive potential for CYP450.     

Shpol'skii luminescence spectroscopy of extracts of coal and coal-tar pitch

Shpol'skii luminescence spectra in straight-chain-alkane matrices at 77 K have been measured from carbon-disulphide extracts of nine coal macerals and a cyclohexane extract of a coal-tar pitch. Twelve individual polycyclic hydrocarbons, containing from three up to ten rings, have been identified. The Shpol'skii effect, which requires little pretreatment of the sample, is particularly sensitive (0.1 ppm) to the carcinogen benz [a] pyrene.     

Benzo[a]pyrene—Environmental Occurrence,Human Exposure,and Mechanisms of Toxicity

Benzo[a]pyrene (B[a]P) is the main representative of polycyclic aromatic hydrocarbons (PAHs), and has been repeatedly found in the air, surface water, soil, and sediments. It is present in cigarette smoke as well as in food products, especially when smoked and grilled. Human exposure to B[a]P is therefore common. Research shows growing evidence concerning toxic effects induced by this substance. This xenobiotic is metabolized by cytochrome P450 (CYP P450) to carcinogenic metabolite: 7β,8α-dihydroxy-9α,10α-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BPDE), which creates DNA adducts, causing mutations and malignant transformations. Moreover, B[a]P is epigenotoxic, neurotoxic, and teratogenic, and exhibits pro-oxidative potential and causes impairment of animals’ fertility. CYP P450 is strongly involved in B[a]P metabolism, and it is simultaneously expressed as a result of the association of B[a]P with aromatic hydrocarbon receptor (AhR), playing an essential role in the cancerogenic potential of various xenobiotics. In turn, polymorphism of CYP P450 genes determines the sensitivity of the organism to B[a]P. It was also observed that B[a]P facilitates the multiplication of viruses, which may be an additional problem with the widespread COVID-19 pandemic. Based on publications mainly from 2017 to 2022, this paper presents the occurrence of B[a]P in various environmental compartments and human surroundings, shows the exposure of humans to this substance, and describes the mechanisms of its toxicity.     

Influence of tall oil and ultrasound treatment on pitch production from semicoking tar or the anthracene fraction

The properties of coal pitch obtained from blends of tall oil and semicoking tar or the anthracene fraction are investigated. Small additions of tall oil to semicoking tar (in the ratio 1: 6) increase the yield of pitch on thermal oxidation and its softening temperature but decrease the coke residue. On ultrasound treatment, chemical transformations of the molecules under the action of cavitation change the characteristics of the pitch produced on thermal oxidation. Primarily, however, the ultrasound permits reduction in the benzo[a]pyrene concentration in the mixture by almost half. On thermal oxidation, the benzo[a]pyrene concentration is further reduced, but most of its mass is concentrated in the pitch.     

Major gaseous and PAH emissions from a fluidized-bed combustor firing rice husk with high combustion efficiency

This experimental work investigated major gaseous (CO and NO_x) and PAH emissions from a 400 kW_th fluidized-bed combustor with a cone-shaped bed (referred to as ‘conical FBC’) firing rice husk with high, over 99%, combustion efficiency. Experimental tests were carried out at the fuel feed rate of 80 kg/h for different values of excess air (EA). As revealed by the experimental results, EA had substantial effects on the axial CO and NO_x concentration profiles and corresponding emissions from the combustor. The concentration (mg/kg-ash) and specific emission (μg/kW h) of twelve polycyclic aromatic hydrocarbons (PAHs), acenaphthylene, fluorene, phenanthrene, fluoranthene, pyrene, benz[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, dibenz[a,h]anthracene and indeno[1,2,3-cd]pyrene, were quantified in this work for different size fractions of ash emitted from the conical FBC firing rice husk at EA = 20.9%. The total PAHs emission was found to be predominant for the coarsest ash particles, due to the effects of a highly developed internal surface in a particle volume. The highest emission was shown by acenaphthylene, 4.1 μg/kW h, when the total yield of PAHs via fly ash was about 10 μg/kW h.     

New Rapid HPLC Method for Separation and Determination of Benzo[A]Pyrene Hydroxyderivatives

A new rapid, one-step semi-quantitative HPLC-MS method applicable for the separation and characterization of the group of total 10 BaP hydroxyderivatives (1-hydroxy benzo[a]pyrene, 2-hydroxybenzo[a]pyrene, 3-hydroxybenzo[a]pyrene, 4-hydroxybenzo [a]pyrene, 7-hydroxybenzo[a]pyrene, 8-hydroxybenzo[a]pyrene, 9-hydroxybenzo[a]py rene, 10-hydroxybenzo[a]pyrene, 12-hydroxybenzo[a]pyrene and benzo[a]pyrene-9,10-dihydrodiol) was developed, involving electrospray ionization technique (ESI) in positive mode. Its qualitative and quantitative characteristics were selected by the analysis of the model OH-BaP mixture consisted of compounds mentioned above. The model system offered the linear response in the whole concentration range used (50–1000 ng.mL^?1) as well as the resolution sufficient for semi-quantitative purposes (R_S > 0.5). Subsequently, the suitability of the developed method was tested on BaP decomposition products to be formed during photooxidation at λ = 365 nm. These analyses confirmed the applicability of the proposed method, succeeding in the identification of 5 BaP hydroxyderivatives formed upon the BaP photooxidation experiment.     

Interaction Analyses of Binary Mixtures of Carcinogenic PAHs Using Morphological Cell Transformation of C3H10T1/2CL8 Mouse Embryo Fibroblasts in Culture

Studies of defined mixtures of carcinogenic polycyclic aromatic hydrocarbons (PAH) have identified three major categories of interactions: antagonism; synergism; and additivity depending on the biological model, tissue, route of exposure, and specific PAH. To understand the bases of these interactions we studied binary mixtures of benzo[a]pyrene (B[a]P) and dibenz[a,h]anthracene (DBA) in transformable C3H10T1/2C18 (C3H10T1/2) mouse embryo fibroblast cells in culture. C3H10T1/2 cells treated with binary mixtures of B[a]P and DBA gave less than additive morphological cell transformation based on response additivity. These results were consistent with those reported in mice and rats on the antagonistic effects of B[a]P and DBA on tumorigenesis. ³²P-Postlabeling DNA adduct studies revealed that DBA reduced B[a]P-DNA adduct levels by 47% with no effect on DBA-DNA adduct levels. This suggests that one mechanism for the inhibition of morphological cell transformation of binary mixtures of B[a]P and DBA is due to alterations in the metabolic activation of B[a]P.     

NEWLY IDENTIFIED PRODUCTS OF BENZENE DROPLET COMBUSTION: POLYCYCLIC AROMATIC HYDROCARBONS OF THREE TO TEN RINGS

Abstract

In order to investigate further the polycyclic aromatic hydrocarbons (PAH) produced by benzene droplet combustion, we have obtained and analyzed a highly-concentrated benzene droplet combustion sample, using high pressure liquid chromatography (HPLC) with diode-array ultraviolet-visible (UV) absorbance spectroscopy. In addition to benzo[k]fluoranthene, we have identified ten large (5- to 10-ring) PAH never before reported as products of benzene pyrolysis or combustion: dibenz[a,c]anthracene, indeno[1,2,3-cd]fluoranthene, anthanthrene, cyclopenta[cd]benzo[ghi]perylene, coronene, dibenzo[a,i]pyrene, cyclopenta[bc]coronene, benzo[a]coronene, naphtho[8,1,2-abc]coronene, and ovalene. In this sample we have also identified three smaller PAH, benz[f]indene, 2-ethynylanthracene, and benzo[c]phenanthrene, never before reported as products of benzene pyrolysis or combustion. In order to document the unequivocal identification of these compounds as benzene droplet combustion products, we present the UV absorbance spectrum of each newly identified benzene product, along with the matching UV spectrum of the respective PAH reference standard. Several of the identifications have required the acquisition of specially synthesized reference standards. Combined with our previous results, the present findings show that 50 individual PAH (and related compounds), of up to 10 rings in size, are produced during benzene droplet combustion.     

Polychlorinated Biphenyls in Sediments from Sicilian Coastal Area (Scoglitti) using Automated Soxhlet,GC-MS,and Principal Component Analysis

A methodology for the PAHs and PCBs congener determination in sediment samples has been revised. We determined the distributions of PAHs and PCBs in the superficial sediments of the Scoglitti (Italy) coastal area to provide data for comparison with other marine systems and to hypothesize the sources. Extraction yield, for PCB, was never less than 60% in most cases, while for PAHs, utilizing perdeuterated surrogate standard (benz[a]anthracene-d₁₂ and anthracene-d₁₀) was never less than 72%. The total concentration of the 16 PAHs investigated, expressed as the sum of concentrations, ∑PAHs, varied from 1–5087 μg/kg of dry matrix, while the ∑ PCBs ranged from detection limit to 36 μg/kg of dry matrix. Linear relationships were found between PAHs concentration and organic matter percentages (R² = 0.60) and water content and organic matter percentages (R² = 0.87). Isomeric ratios were used for discriminating between pyrolitic and petroleum origin. The principal component analysis (PCA) has been conduced to discriminate the different sampling sites in internal or external harbor area.     

Geoecology of benzo[<Emphasis Type="Italic">a</Emphasis>]pyrene as a coal pyrolysis product

The accumulation of benzo[a]pyrene as a coal pyrolysis product in the soil cover of Chelyabinsk and its surroundings, which are characterized by a high concentration of industrial enterprises and power plants within the confines of the city, was evaluated. The concentrations of this carcinogenic substance in various soils were found higher than the maximum permissible concentration (20 μg/kg).