Aromatic compounds continued polycyclic

Figure 1. Thermodynamic equilibrium in atmospheres of varying elemental proportions. The ternary diagram shows all compositions of systems containing carbon, hydrogen, and oxygen (each point represents 100% of the three components). Lower curves indicate the potential formation of solid carbon if equilibrium could be attained. Dashed curve holds at 500°K., the continuous one at 700°K. The upper lines indicate the asphalt threshold, the dashed one at 500° K., and the continuous one at 700° K. Above this threshold, thermodynamic equilibrium favors the formation of large proportions of polycyclic aromatic compounds ( asphalt ) ana a lesser increase of most of the other families of compounds. The dots through points A to C indicate the points used in the computations for Figure 2 (6).

Of all the short-term assays, the Ames Salmonella test is clearly the best validated and most widely used and will continue to be so for a number of years to come. The assay has an excellent record for identifying organic carcinogens, particularly carcinogens which are in the aromatic amine and polycyclic hydrocarbon classes. " In addition, positive results in the Ames assay and several other short-term mutagenesis assays, have been predictive of carcinogenic activity in rodent assays for a number of compounds with widespread human exposure. Examples of these include the food preservative furylfuramide AF-2 which was used extensively in Japan from 1965 to about 1977 the flame-retardant tris-B-P (tris[2,3-dibromopropyl]phosphate) which was used to treat children s sleepwear from 1972 to 1977 and aromatic amine components of hair dye preparations. 

Bromination of Aromatic Compounds. Studies on the bromination of monocyclic and polycyclic aromatic compounds with NBS have continued and in particular the bromination of phenols and naphthols has received attention, e.g., the conversion of 6 into 7 (eq 35). 

Although most of the oil from the lakes has been removed or has been the subject of heavy weathering, the lakebeds still contain a large amount of oil, which cannot be easily removed. Analysis of samples indicated that the composition of the oil in the lakes continues to change [77]. The chemical composition of weathered oil showed a decrease in aromatic compounds, and an increase in resins and higher polycyclic aromatic hydrocarbons. This inaeases the hazard potential of oil lakes. Heavily contaminated soils may eventually erode and be resuspended and transported to populated areas during dust storms and could cause health hazards [35]. There is also the possibility of contaminating soil with heavy metals, particularly nickel, vanadium, chromium, and lead. 

Air quality is important from both a health and a safety perspective. In the USA, the National Institute for Occupational Safety and Health (NIOSH) and the Occupational Safety and Health Administration set limits of exposure to over 2000 different chemicals or classes of respiratory irritants [11, 12], Many of the compounds that are monitored indoors are of similar interest to outdoor assessment, such as in the atmosphere and stratosphere. VOCs emitted from industrial operations are continuously monitored as required by US and local Environmental Protection Agencies. Power plants and waste incinerators are required to follow emission guidelines for harmful combustion gases, including CO and NO, as well as other combustion by-products, including polycyclic aromatic hydrocarbons, phenols, and hy-... 

The toxification of benzo[a]pyrene and most other polycyclic aromatic hydrocarbons to mutagenic intermediates by continuous cell lines has been reported dozens of times, whereas toxification of aflatoxin Bj to mutagenic intemediates in some cell lines does not occur.225 These data can be explained by the fact that the forms of P-450 necessary for polycyclic-hydrocarbon toxification remain in cultured primary and continuous cell lines, whereas the forms of P-450 responsible for the 2,3-oxide formation of aflatoxin Bj disappear rapidly in culture, for unknown reasons. Studies involving cultured human tissues may have this same major liability. The choice of cell culture for any particular compound therefore can be important. 

From these inventories and data, it is clear that society is facing an enormous problem of contamination. Many of the polluting compounds that are continuously dispersed are products of industrial activities such as phenols and halogenated phenols, polycyclic aromatic hydrocarbons (PAH s), endocrine disruptive chemicals (EDC), pesticides, dioxins, polychlorinated biphenyls (PCB s), industrial dyes, and other xenobiotics. In this chapter, we critically review the literature information on the enzymatic transformation of these polluting xenobiotics. This work is focused on peroxidases as enzymes able to transform a variety of pollutant compounds with the aim to reduce their toxicity and their environmental impact. 

The photochemistry of polycyclic aromatic hydrocarbons (PAHs) and poly-chlorobiphenyls (PCBs) in water and on solids was reviewed in this series in 1999 [1]. The large interest in this field was due to the fact that many PAHs and mixtures of PCBs are on the United States Environmental Protection Agency s fist of priority pollutants (see [1] for the fist of compounds). Photochemists wanted to know what the fate of these materials in the environment is when exposed to sunlight and if one could use photochemistry to remediate contaminated sites. This interest has continued and will be the focus of the present review. The review covers the recent literature through the middle of 2003. 

In 2003, urban air pollution was monitored at 76 stations (44 and 32 operated by the Ministry of Health and the Ministry of the Environment, respectively) located in 27 cities involved in the Monitoring System (SZU, 2004). In 2003, sulphur dioxide (SO2), nitrogen oxides (NO/N02/NOx), particulate matter (TSP and/or suspended PMio fractions), and mass concentrations of selected metals (arsenic, chromium, cadmium, manganese, nickel and lead) in particulate matter samples were monitored in all the cities of the Monitoring System except for Melnik. The SO2 measurements in the Public Health Service network were terminated at all the manual stations in the cities with CHMI stations in the cities without a CHMI station, measurements are made during the heating season only). Concentrations of carbon oxide, ozone, polycyclic aromatic hydrocarbons (PAHs) and volatile organic compounds (VOCs) continue to be monitored selectively in a number of the monitored cities. 

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