PAH quinones

The sample sizes collected by our PMj 5 sampling systems are insufficient to conduct detailed chemical analyses. However, available data for size-fractionated fine particulate matter indicates that PAH quinones, including 1,4-naphthoquinone, 5,12-naphthacenequinone, benz[a]anthracene-7,12-dione, and anthracene-9,10-dione, are important organic components (41, 42). The detection of these molecular species that are similar in structure to semiquinone-type radicals supports the assignment of our EPR signals. 

Particulates are another source of respiratory irritation when inhaled. In urban environments, diesel exhaust particles and fly ash residue from power plant oil combustion are the main contributors of respirable particulates of less than 10 pm diameter (PM 10). These contain mixtures of lipo-philes and hydrophiles including various metals, acid salts, aliphatic hydrocarbons, PAHs, quinones, nitroaromatic hydrocarbons, andaldehydes. 151 Diesel combustion particulates contain large surface areas that can adsorb large quantities of organic compounds and deliver these to respiratory tract tissue. Other inhaled particulates can adhere to lung surfaces and adsorb and bond other vapors that are inhaled, thereby increasing their toxicities. PM2.5 particulates (those with diameters of less than 2.5 pm) that reach the lower respiratory tract as far as the alveoli are more toxic than PM 10 particulates of the same composition. 16 ... 

The activity of quinone reductase, a major protective enzyme, was increased 2-3-fold in first trimester human placental extracts in vitro when incubated for 6 hours with benz[a]anthracene. dibenz[a,h]anthracene, and chrysene at a concentration of 50 jmol (Avigdor et al. 1992). Based on these results, it can be postulated that the early placenta is capable of metabolizing certain toxic xenobiotics such as PAH quinone metabolites to inactive intermediates thereby protecting the developing embryo. 

Possible atmospheric reaction products are oxy-, hydroxy-, nitro- and hydroxynitro-PAH derivatives (Baek et al. 1991). Photochemical oxidation of a number of PAHs has been reported with the formation of nitrated PAHs, quinones, phenols, and dihydrodiols (Holloway et al. 1987 Kamens et al. 1986). Some of these breakdown products are mutagenic (Gibson et al. 1978). Reaction with ozone or peroxyacetyinitrate yields diones nitrogen oxide reactions yield nitro and dinitro PAHs. Sulfonic acids have also been formed from reaction with sulfur dioxide. 

Hinze was the first to investigate the capabilities of micellar bile salt mobile phases [11, 12]. He found that a significant amount ( 5% v/v) of a long chain n-alcohol (pentanol, hexanol or heptanol) was useful to minimize the bile salt adsorption on the C18 stationary plmse. A wide range of solutes could be separated by these phases, PAHs, quinones, steroids, indoles, polar and lipophilic vitamins. These phases were also able to resolve optically big enantiomers such as binaphthyl derivatives [12]. Such compounds are... 

Fernandez and Bayona [618] developed a method for the fiactionation of polyaromatic hydrocarbons from dichloromethane extracts of air particulates and marine sediment. The resulting fractions were quantitated by GC/MS. A silica column I = 254 nm or 254 nm, ex 390 nm, em) generated the following fractions PCB, PAH, N02-PAH/2°-amine-PAH, keto-PAH, keto-PAH/quinones, quinones, 3°-amine-PAH, and 3°-amine-PAH/hydroxy-PAH. The separation required a 70-min 100/00/100 hexane/dichloromethane gradient. Levels of 47 compounds were monitored, typically well below the pg/g range. 

Reactive Metabolites of PAHs. A wide variety of products have been identified as metabolites of PAHs. These include phenols, quinones, trans-dihydrodiols, epoxides and a variety of conjugates of these compounds. Simple epoxides, especially those of the K-region, were initially favored as being the active metabolites responsible for the covalent binding of PAH to DNA. Little direct experimental support exists for this idea (62.63,64) except in microsomal incubations using preparation in which oxidations at the K-region are favored (65,66). Evidence has been presented that a 9-hydroxyB[a]P 4,5-oxide may account for some of the adducts observed in vivo (67.68) although these products have never been fully characterized. 

Finally, we have studied the metabolism of a series of PAH with decreasing IP. In these metabolic studies with Aroclor-induced rat liver microsomes, the formation of quinones was measured in the presence of NADPH or cumene hydroperoxide as cofactor. 

As presented in Table II, no quinones are obtained with NADPH for dibenz[a,h]anthracene and benz[a]anthracene, whereas with cumene hydroperoxide a trace amount of benz[a]anthracene quinone is observed. For the PAH with low IP, quinones are formed in the presence of both cofactors. The relationship between IP and formation of quinones constitutes further evidence that these metabolites are obtained by an initial one-electron oxidation of the PAH with formation of its radical cation. 

Structures of compounds representing several classes of O-PACs identified in ambient air, e.g., PAH ketones, quinones, anhydrides, and lactones, are shown in Table 10.4. 

However, reactions of PAHs in ambient air to form more polar species (e.g., nitro-PAHs, ketones, quinones, lactones, and dicarboxylic acids) greatly enhance their solubilities in aqueous systems. This has major implications when one considers the distribution of PAHs, and their atmospherically formed PAC derivatives, through the air, water, and soil environments. These increases in solubility upon reaction are important not only from an environmental chemistry perspective but also in terms of possible impacts on public health and ecosystems, e.g., in both the exposure and the health effect... 

Complex mixtures of oxidized products are produced in the ozonolysis of BaP on solid substrates. For example, BaP deposited on a glass fiber filter and exposed to 1 ppm 03 in air primarily formed products characteristic of the ring-opening mechanism, e.g., dialdehydes and dicarboxylic and ketocarboxylic acids. However, some quinones and phenols, were also formed. For details on the mechanisms and O-PAH products of these BaP-Ov gas-solid substrate reactions, see Van Cauwenberghe et al. (1979) and Van Cauwenberghe and Van Vaeck (1983 and references therein). 

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