Pure Polycyclic Aromatic Hydrocarbons Research Articles

Identification and production of a rhamnolipidic biosurfactant by a Pseudomonas species

A glycolipid-producing bacterium, Pseudomonas aeruginosa GL1, was isolated from the soil contaminated with polycyclic aromatic hydrocarbons (PAH) from a manufactured gas plant. The glycolipid produced was characterized in detail by chromatographic procedures as a mixture of four rhamnolipids, consisting of different associations of rhamnose and hydroxy fatty acids: the main component was monorhamnosyl di-3-hydroxydecanoic acid. The rhamnolipid composition presented marked analogies with a defined part of P. aeruginosa outer membrane lipopolysaccharides (lipopolysaccharide band A). Rhamnolipid production was stimulated under conditions of nitrogen limitation. Glycerol yielded higher productions than did hydrophobic carbon sources. Cell hydrophobicity decreased during growth on glycerol and on n-hexadecane whereas glycolipid production increased. P. aeruginosa GL1 was found to be unable to grow on a variety of 2, 3 and 4 cycle PAH. However, it was shown to persist after at least 12 subcultures in a bacterial population growing on a mixture of pure PAH, suggesting a physiological role for rhamnolipid as a means to enhance PAH availability in a mutualistic PAH-degrading bacterial community.

Bacterial and human cell mutagenicity study of some C18H10 cyclopenta-fused polycyclic aromatic hydrocarbons associated with fossil fuels combustion.

A number of isomeric C18H10 polycyclic aromatic hydrocarbons (PAHs), thought to be primarily cyclopenta-fused PAHs, are produced during the combustion and pyrolysis of fossil fuels. To determine the importance of their contributions to the total mutagenic activity of combustion and pyrolysis samples in which they are found, we characterized reference quantities of four C18H10 CP-PAHs: benzo[ghi]fluoranthene (BF), cyclopenta[cd]pyrene (CPP), cyclopent[hi]acephenanthrylene (CPAP), and cyclopent[hi]aceanthrylene (CPAA). Synthesis of CPAA and CPAP is described. The availability of reference samples of these isomers also proved to be an essential aid in the identification of the C18H10 species often found in combustion and pyrolysis samples. Chemical analysis of selected combustion and pyrolysis samples showed that CPP was generally the most abundant C18H10 isomer, followed by CPAP and BF. CPAA was detected only in pyrolysis products from pure PAHs. We tested the four C18H10 PAHs for mutagenicity in a forward mutation assay using S. typhimurium. CPP, BF, and CPAA were roughly twice as mutagenic as benzo[a]pyrene (BaP), whereas CPAP was only slightly active. These PAHs were also tested for mutagenic activity in human cells. In this assay, CPP and CPAA were strongly mutagenic but less active than BaP, whereas CPAP and BF were inactive at the dose levels tested. Also, the bacterial and human cell mutagenicity of CPAA and CPAP were compared with the mutagenicity of their monocyclopenta-fused analogs, aceanthrylene and acephenanthyrlene. Although the mutagenicities of CPAP and acephenanthrylene are similar, the mutagenic activity of CPAA is an order of magnitude greater than that of aceanthyrlene.

Environmental Transformation, Photolysis of Fluorescing Petroleum Compounds in Marine Waters

A great variety of fluorescing compounds - mainly polycyclic aromatic hydrocarbons (PAHs) which are of concern in environmental and public health risk assessment due to their carcinogenic properties - exists as a complex mixture in petroleum, which makes their separation and identification difficult, if not impossible. Ultraviolet (UV) fluorescence spectroscopy offers a relatively simple way to characterize and quantify these compounds in environmental samples. PAHs are known to be sensitive to photochemical reactions rather than to biological oxidation. Several studies carried out with pure PAH compounds demonstrated their fast photolysis, half-lives of a few minutes to a few hours have been observed, which depend on the irradiation light flux. The objective of the present study was to describe photolysis characteristics of mixtures of fluorescing petroleum compounds exposed to sunlight. Crude oil and benzo(a)pyrene (BaP) were used as model mixture of fluorescing compounds in seawater. Solar irradiation conditions were selected to characterize maximum photolysis rates at 29 °N latitude. In addition to the characteristics of the irradiation light, reactor geometry, level of dispersion of the petroleum compounds and the presence of particulate matter influenced significantly the reaction rate coefficients. Photolysis of BaP was described with a first-order rate coefficient, whereas photolysis of the other compounds, quantified by fluorescence intensity at different wavelengths, was characterized with a multicomponent equation. BaP can be considered as an internal actinometer in photolysis experiments with PAH mixtures. The level of dispersion affected the photolysis rates, which were highest in the dissolved and chemically dispersed samples. Ratios between fluorescence intensities at different wavelengths allowed comparison with the characteristics of actual environmental samples, providing additional information on their weathering history.

Covalent binding of dibenzpyrenes and benzo[a]Pyrene to DNA: evidence for synergistic and inhibitory interactions when applied in combination to mouse skin

Several well-documented examples of human exposure to carcinogens involve complex mixtures of polycyclic aromatic hydrocarbons (PAHs). Although the biological properties of many pure PAHs have been investigated, less is known about their effects when present as components of mixtures. As the ability to form DNA adducts in vivo is generally indicative of carcinogenic activity of PAHs, we have compared the DNA binding potencies of dibenzo[a,e]pyrene (DB[a,e]P), dibenzo[a,e]pyrene (DB[a,h]P), dibenzo[a,i]pyrene (DB[a,i]P), dibenzo[a,l]pyrene (DB[a,l]P) and benzo[a]pyrene (B[a]P), when applied topically, either singly or in combination, to the skin of male Parkes mice. DNA isolated from the skin and lungs was analysed by 32P-postlabelling. The adducts formed by each PAH exhibited markedly different chromatographic mobilities on polyethyleneimine-cellulose TLC plates. The relative binding potencies of the compounds in both skin and lungs were: DB[a,l]P much greater than B[a]P greater than DB[a,h]P greater than DB[a,i]P greater than DB[a,e]P, in good agreement with their reported carcinogenicities in mouse skin. The majority of adducts were removed from DNA within 21 days of treatment, but low levels of adducts were found to persist for at least 3 months in both tissues. When DB[a,l]P, DB[a,e]P and B[a]P were applied together to mouse skin, a total binding 31% lower than expected was detected, while with a mixture of DB[a,e]P and B[a]P the binding to DNA in skin was 65% higher than expected from the binding levels of the carcinogens when applied singly. Other binary combinations of these three PAHs gave adduct levels similar to the sum of the binding levels of the individual components when applied singly. The results demonstrate the usefulness of 32P-post-labelling for the assessment of the DNA binding potencies of PAHs in mouse tissues, and for the detection of interactions between components of mixtures of carcinogens.

Characterization of TCDD-receptor ligands present in extracts of urban particulate matter

Extracts of filter-collected urban airborne particulate matter contain compounds which can competitively inhibit 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) binding to the rat liver TCDD-receptor protein. The concentration of conventional polycyclic aromatic hydrocarbons (PAHs) or chlorinated dioxins and dibenzofurans cannot account for more than 1%–30% of the observed competition for TCDD-binding to the receptor protein. Chemical fractionation of an extract of a well-characterized particulate air sample collected in Washington, DC showed the highest activity residing in the hexane/benzene fraction, although significant levels of activity were found also in other fractions. Analysis of extracts of gasoline exhaust particulate matter and fractions thereof gave similar results. A series of pure PAHs and nitro-and chloroderivatives of PAHs was tested for competition with TCDD for receptor binding. Among the most potent compounds with EC 50-values similar to tetrachlorodibenzofuran were 1- and 3-nitrobenzo( a)-pyrene. Other highly active compounds included dibenzo( a,h)anthracene, benzo( j)fluoranthene, benzo( k)fluoranthene, picene, indeno(1,2,3- cd)pyrene, 3-nitroperylene, and 3,9-and 3,10-dinitroperylene. the EC 50-value for aryl hydrocarbon hydroxylase induction in hepatoma cells and the EC 50-value for TCDD-receptor binding were similar for dibenzo( a,h)anthracene and for a PAH-containing fraction of an extract of gasoline exhaust particulates. The presence of active TCDD-receptor ligands in extracts of urban particulate matter and their ability to be taken up by cells and cause biological alterations represent a potential health risk. The identity of these compounds are largely unknown although certain PAHs and possibly some nitroderivatives of PAHs are likely to play a role.

The role of polycyclic aromatic hydrocarbons (PAH) in the formation of smoke particulates during the combustion of polymeric materials

The chemical analysis of stable combustion products found in the particulate smoke of polymeric materials is described. The chemical nature of the products produced during flaming and non-flaming modes yeilds valuable information on the possdible role of polynuclear aromatic hydrocarbons (PAH) in the smoke formation process. Samples of polyethylene, polypropylene, polymethylmetahcrylate and polystyrene were studied under controlled thermalo fluxes, and the first three showed similar trends: (1) In the non-flaming mode, aliphatic compounds predominated in the extractable portion of the particulate smoke. (2) In the flaming mode, PAH predominated in the extractable fraction. (3) In the non-flaming mode, of the PAH present, three- and four-membered ring compounds predominated, (4) In the flaming mode, again three- and four-membered ring compounds predominated, but many other PAH up to six-metmbered rings were found. Polysteyren gave rise to degradation products stillcontaining the basic-styrene-derived C 6 H 5 −C 2 units. The quantitative studies of polymer particulate smoke, taken together with further studies of combustion products of pure PAH, leads to a postulated chemical smoke formation pathway.

Analysis for polynuclear aromatic hydrocarbons in working atmospheres by computerized gas chromatography-mass spectrometry

Polynuclear aromatic hydrocarbons in particulate matter from working atmospheres have been analyzed by a glass capillary gas chromatography—mass spectrometer—computer system which has high separation efficiency and is capable of separating and identifying these complex mixtures. More than one hundred polynuclear aromatic hydrocarbons have been identified in samples from a coke plant and an aluminum smelter, including both pure polycyclic aromatic hydrocarbons and compounds where a CH-group is substituted with the hetero atoms oxygen, nitrogen, or sulfur. The occurrence of polynuclear aromatic hydrocarbons in working atmospheres is compared to that in ambient air and emissions from other sources.

Chemical Constitution and Carcinogenic Activity

Publisher Summary The study of chemical carcinogenesis dates from 1915, when cancer was first produced experimentally by the long-continued application of coal tar to the ears of rabbits, but it was not until 1930 that cancer was produced by the application of a pure polycyclic aromatic hydrocarbon, 1,2,5,6-dibenzanthracene, to the skin of mice. It is commonplace in all studies of the relation between chemical constitution and biological action that the same biological end result can frequently be brought about by different classes of chemical compounds acting by different mechanisms. Complex formation only occurs with molecules of suitable molecular complexity, and it is prevented by large substituents and by the presence of substituents in certain parts of the molecule; it does not occur if the molecule is buckled by hydrogenation. Complex formation is greatly facilitated by the presence of an activated K region, but the necessary degree of activation may vary considerably, depending on the molecular complexity. The carcinogenic azo compounds enter into some form of complex with a cellular receptor so that the factors that influence the ease of formation and stability of such a complex may well be of importance. The electron density of the K region may be a controlling factor, but large substituents may offer steric hindrance to the formation of the complex.

The production of cancer by pure hydrocarbons.—Part I

Hydrocarbons are known to have the power to produce cancer in mice, for the carcinogenic mixtures obtained by heating acetylene or isoprene in an atmosphere of hydrogen (Kennaway, 1924, 1925) can consist only hydrocarbons. Moreover, the powerful fluorescenece of these and other carcinogenic mixtures ( e. g. , gas-works tar; shale oil; heated petroleum; products of the action of heat upon cholesterol, yeast, skin, muscle, and hair, and of the action of aluminium chloride upon tetralin) suggests that such hydrocarbons are of the polycyclic aromatic type. These mixtures gave a characteristic threebanded fluorescence spectrum, which resembled in character that of 1:2-benzanthracene. This significant observation led to the examination for carcinogenic action of a large number of pure polycyclic aromatic hydrocarbons of known molecular structure, particular attention being paid to compounds related to 1:2-benzanthracene (I). One such hydrocarbon, 1:2:5:6-dibenzanthracene (II), was prepared by the method of Clar (1929, a ), and gave positive results. When the first four cancers produced in mice by this substances had been obtained, a preliminary account of the experiments was published (Hieger, 1930; Kennaway, 1930). We now have specimens of 102 cancers and 31 papillomas produced by this compound and its simple methyl derivatives, while various other compounds have given negative results. The production of tumours of subcutaneous tissue by injection of fatty media containing 1:2:5:6-dibenzanthracene has been recorded elsewhere (Burrows, Hieger and Kennawsy, 1932), and the numerous tumours of the peritoneal cavity which have been produced by similar methods are described by Burrows (1932).