Subject polycyclic aromatics

Bioventing technology was developed by the U.S. EPA Risk Reduction Engineering Laboratory to treat soil contaminated by numerous industrial wastes, which is subjected to aerobic microbial degradation, especially to promote the degradation of polycyclic aromatic hydrocarbons.65 It uses a series of air injection probes, each of which is attached to a low-pressure air pump. The air pump operates at extremely low pressures to allow the inflow of oxygen without volatilization of contaminants. Additional additives such as ozone or nutrients may also be supplied to stimulate microbial growth.77... 

As observed in mammalian models, the immune system of fishes is a sensitive target organ system to evaluate toxicity. For a more thorough review of environmental immunotoxicology in fishes, with reference to specific classes of xenobiotics, readers are referred to several reviews that deal with the subject over a span of nearly three decades [45-47, 54-57], While fish in the environment may be exposed to a variety of xenobiotics, the most frequently investigated xenobiotics are the polycyclic aromatic hydrocarbons (PAHs) and halogenated aromatic hydrocarbons (HAHs) due to the presence and activation of the aryl hydrocarbon receptor (AhR) in fish, and heavy metals due to their ubiquitous environmental distribution. 

N-demethylase activity was monitored by the CBT, and 7-N-demethylase activity was monitored by the caffeine urinary metabolite ratio (CMR). PBB-exposed subjects had higher CBT values (p<0.02) than urban nonsmokers, but tire values were comparable to those of urban smokers. The correlation between serum PBB levels and the CBT value was poor (r ().2). The CMR value in PBB-exposed subjects was also higher than that of urban nonsmokers (p<0.05) there was no correlation between serum PBB levels and CMR values. Generally, smokers have higher CBT values than nonsmokers due to the presence of polycyclic aromatic hydrocarbons (PAH) in tobacco smoke, which induce CYPIA (Kotake et al. 1982). 

In this chapter we shall discuss LCA in the context of protocols for the analysis of polychlorinated biphenyl (PCB) and polycyclic aromatic hydrocarbon (PAH) in surface water using two different extraction techniques,11 and the LCA of the utilization of different solvents.12-26 Generally speaking, this is the beginning of the use of LCA to assess the environmental impact of analytical protocols at the moment, there are not many papers on this subject, but this situation is sure to improve in the near future. 

These studies demonstrated that DNA-binding can be a reliable probe of metabolic activation. In contrast to studies of metabolites per se, which usually involve large numbers of metabolite intermediates, DNA-binding monitors only chemically reactive metabolites. Also, if there is no selective repair of specific adducts, DNA-binding monitors the cumulative production of metabolites over time, while direct measurement of metabolites can show the metabolite spectrum only at the time observed. This can be particularly critical for studies of activation of complex chemicals such as polycyclic aromatic hydrocarbons whose primary metabolites are subject to secondary and tertiary metabolism (8). 

Direct photolysis processes on the surface of airborne particulate matter can be important sinks of sunlight-absorbing compounds (see [28] for a recent review by our group on this subject), and in particular of polycyclic aromatic hydrocarbons (PAHs) [11]. The particles can protect adsorbed substrates against reaction with species such as OH and N03 from the gas phase, and enhance the relative role of direct photolysis. However, it should be considered that black carbonaceous... 

Mercury. - Cadmium. - Polycyclic Aromatic and Heteroaromatic Hydrocarbons. - Fluorocarbons. -Chlorinated Paraffins. - Chloroaromatic Compounds Containing Oxygen. - Organic Dyes and Pigments. - Inorganic Pigments. - Radioactive Substances. - Subject Index. 

In this chapter, the different steps in the assessment of mixture exposure are discussed. The chapter starts from emission scenarios and subsequently discusses transformation processes taking place in the environment and their effects on mixture composition. Next, bioavailability is discussed, and exposure scenarios for both humans and biota in the environment are described. These descriptions also consider methods to assess exposure to mixtures. Most data available on mixture exposure are restricted to North America and Europe, but we recognize that there are emerging problems in other regions of the world. We restrict our discussion to man-made chemicals and those natural chemicals subject to regulation (metals, polycyclic aromatic hydrocarbons (PAHs)), because these represent the most well-studied group and the current priorities for risk assessment. 

In addition to the need to monitor known problematic compounds, newer compounds are being identified as potential threats to humans and as such need to be monitored in the atmosphere. For example, researchers reported (10) that several chemical and instrumental analyses of HPLC fractions provided evidence for the presence of /V-nitroso compounds in extracts of airborne particles in New York City. The levels of these compounds were found to be approximately equivalent to the total concentrations of polycyclic aromatic hydrocarbons in the air. Since 90% of the N-nitroso compounds that have been tested are carcinogens (10), the newly discovered but untested materials may represent a significant environmental hazard. The procedure involved collecting samples of breathable, particulate matter from the air in New York City. -These samples were extracted with dichloro-methane. Potential interferences were-removed by sequential extractions with 0.2 N NaOH (removal of acids, phenols, nitrates, and nitrites) and 0.2 N H2S04 (removal of amines and bases). The samples were then subjected to a fractional distillation and other treatments. Readers interested in the total details should consult the original article (10). Both thin-layer chromatography (TLC) and HPLC were used to separate the compounds present in the methanolic extract. 

Scheme IS dq>icts a high yield, general method for specific ortho allgriation of polycyclic aromatic hydrocarbons. In this example, biphenyl is subjected to reductive methyladon followed by oxidative rearrangement with trityl tetrafiuoioborate to give 2-methylbipbenyl. In unsymmetrical substrates the regioselectivity is poor, phenanthiene gives a 3 2 mixture of 4-methyl- and 1-mediyI-phenanlhrene.

These results show that pattern recognition can be used as an effective tool to characterize polycyclic aromatic hydrocarbon carcinogens. Using a set of only 28 molecular structure descriptors, linear discriminants can be found to correctly dichotomize 191 out of 200 randomly selected PAH s. This same set of 28 descriptors supports a linear discriminant function that has an average predictive ability of over ninety percent when subjected to randomized predictive ability tests. 

---