Coal identifying PAHs

Figures 4, 5, and 6 are MI fluorescence spectra of Fractions IV, V, and VI, respectively, from the LC of a sample of Synthoil, a catalytic hydrodesulfurization process coal liquid. By comparison with MI fluorescence spectra of standard PAH, the following compounds can be identified conclusively in the indicated fractions pyrene (IV), benz[a]-...

Other studies on coal were performed using pyrolysis, such as the measurement of the level of sulfur containing compounds in coal [27,28], or evaluation of polynuclear aromatic hydrocarbons (PAH) in coal [29]. The generation of PAH in coal pyrolysis is an important issue, as some of these compounds are known to have carcinogenic properties. A list of PAHs identified in coal pyrolysates is given in Table 14.2.2. The yield of PAH in coal pyrolysate depends to some extent on the coal type but mainly on the pyrolysis temperature. The variation of PAH levels as a function of temperature for several bituminous coals is shown in Figure 14.2.3. The yields of other pyrolysis products of coal were also shown to be temperature dependent [30]. 

PAH diol epoxide-DNA adducts have not only been detected in rodent tissues in experimental systems after PAH exposure, but have also been identified in (a) populations exposed to complex mixtures containing PAHs, (b) foundry workers (Perera et al. 1988 Hemminki et al. 1988), (c) coke oven workers (Rojas et al. 1995 Pavanello et al. 1999), (d) cigarette smokers (Lodovici et al. 1998 Rojas et al. 1995), (e) chimney sweeps (Pavanello et al. 1999), and (f) populations exposed to smoky coal combustion mixtures (Mumford et al. 1993). Some bay- or fjord-region diol epoxides form DNA adducts in the human p53 tumor suppressor gene at sites that are hotspots for lung cancer (Smith et al. 2000). 

The major chemicals in coal tar creosote, coal tar, and coal tar pitch that can cause harmful health effects are polycyclic aromatic hydrocarbons (PAHs), phenol, and cresols. Coal tar pitch volatiles vary depending on the makeup of the coal tar product that is being heated. About 300 chemicals have been identified in coal tar creosote, but as many as 10,000 other chemicals may be in this mixture. Because coal tar creosote is the major type found in the environment and at hazardous waste sites in the United States, we will emphasize its effects on human health in this profile. The health effects of coal tar and coal tar pitch will also be described. 

No medical test will determine if you have been exposed to wood creosote, coal tar creosote, coal tar, coal tar pitch mixtures, or coal tar pitch volatiles. However, chemicals contained in creosote (such as PAHs or phenol) may be detected and measured in body tissues (organs, muscle, or fat), urine, or blood after exposure to creosote. Typically, this may be done for employees in industry who work with coal tar creosote, coal tar, and coal tar pitch to monitor their exposure. For example, the metabolite 1-hydroxypyrene, which can be detected in urine after exposure to pyrene, has been used to test for exposure to creosote because pyrene is a component of creosote. This test would determine only whether you have recently been exposed to pyrene, but cannot positively identify the source of the pyrene as creosote or accurately predict whether you will experience any adverse health effects. Moreover, analyses of urine samples for 1-hydroxypyrene are not normally done in a doctor s office because they require special equipment. 

The derivation of the MRL is further complicated by the variability of the mixture s composition among wood creosote and coal tar creosote samples and the differences in mode of action of the individual components. The mixtures composition is dependent on the sources and preparation parameters of wood creosote and coal tar creosote and, as a result, the creosote components are rarely consistent in their type and concentration. Hence, toxicological evaluations of one creosote sample, for instance, are most likely inadequate for extrapolation to other creosote samples, unless their compositions are similar. An example of the composition variability among creosote samples was presented by Weyand et al. (1991). In that study, the concentrations of several PAHs were analyzed in four samples of manufactured gas plant (MGP) residue, a form of coal tar. All of the PAHs identified exhibited 2- to nearly 20-fold differences in concentration among the four samples. Benzo[a]pyrene, a component whose individual toxicity has been examined extensively, ranged from nondetectable levels (detection limit 0.3 g/kg) to 1.7, 6.4, and 3.9 g/kg of coal tar. Other studies that illustrate the variability of samples include Wrench and Britten (1975), Niemeier et al. (1988), and Emmett et al. (1981). 

It is evident in both human and animal studies that hydroxylation is a principal oxidative pathway of PAH metabolism, and consequently, coal tar creosote metabolism. In these studies, there were no discussions to suggest that the researchers attempted to identify other metabolites. 

Effect. The formation of benzo[a]pyrene-DNA adducts has been demonstrated (Pavanello and Levis 1992 Zhang et al. 1990) and may also serve as a biomarker of PAH-induced carcinogenicity. However, these adducts are not specific for coal tar creosote exposure, as exposure to benzo[a]pyrene from sources other than coal tar creosote can occur. Studies to identify and measure effects more diagnostic of coal tar creosote-specific injury would be useful. Also, increasing the sensitivity of these tests would be valuable in evaluating the health status of individuals who have been exposed to low levels of creosote. 

The composition of the creosote mixture is dependent on the sources and preparation parameters of the coal tar, and as a result the creosote components are rarely consistent in their type and concentration. An example of the composition variability among creosote samples was recently presented by Weyand et al. (1991). In that study, the concentrations of several PAHs were analyzed in four coal tars. All of the PAHs identified exhibited 2-fold to nearly 20-fold differences in concentration among the four samples. 

AG inv= 13.2 0.5 kcal/mol [109].Theplanarbenzo[l,2,3-frc 4,5,6-frY]dicoro-nene (56) represents the largest PAH which so far has been unambiguously identified in coal tar as well as the largest pencondensed aromatic hydrocarbon for which a crystal structure has been determined [ 1 lOd]. 

LC-MS-MS using a high-pressure quadrupole collision cell, following APCI-MS, produced collision-induced dissociation with adequate fragmentation so that isomers could be identified by peak-area ratios. This technique was applied to the analysis of PAHs in coal tar extract SRM 1597 with standard addition. Twelve PAHs were detected at levels that were close to or within certified limits. 

The authors also examined coal and wood particles within the sediment. They found a larger concentration of PAH within these particles compared to the silica particles. They also determined that while organic carbon molecules were present uniformly throughout these particles in mixtures of aliphatic and aromatic (cyclic) forms, the PAH was concentrated at the surfaces of these particles. The conclusions derived from this powerful combination spectroscopies will allow a more successful approach to remediation of the Milwaukee Harbor. These results could also have a larger impact, since they show the feasibility of identifying chemical constituents and their distributions in sediments which are important in planning remediation efforts in different environs. 

Coal tar is produced by the carbonization, or coking, of coal. Its color is almost black, occurs as a thick liquid or semisolid, and is only slightly soluble in water. It has a specific gravity of 1.18-1.23. A specific gravity of 1.20 has been determined for the Minnesota Slip coal tar. Streitz and Johnson (2005) described how their use of a laser-induced fluorescence (LIF) tool indicated a thick sequence of material identified as coal tar constituents in the back half of Minnesota Slip. Significantly, this location is near the 2002 project dredging site. PAH analysis of a Minnesota Slip coal tar sample taken from the Erie Pier site in 2005 is summarized in Table 32.5. Note the extreme values, that is, percent total PAH. 

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