Polycyclic aromatic hydrocarbons alkyl homologs

Polycyclic aromatic hydrocarbons (PAHs, sometimes also called polynuclear aromatics, PNA) are a hazardous class of widespread pollutants. The parent structures of the common PAHs are shown in Fig. 4 and the alkylated homologs are generally minor in combustion emissions. PAHs are produced by all natural combustion processes (e.g., wild fires) and from anthropogenic activity such as fossil fuels combustion, biomass burning, chemical manufacturing, petroleum refining, metallurgical processes, coal utilization, tar production, etc. [6,9,15,18, 20,24,131-139]. 

Polycyclic aromatic compounds (PAC) are a significant environmental chemical group, with an associated health effect. PACs includes PAH (polycyclic aromatic hydrocarbon), PASH (polycyclic aromatic sulfur hydrocarbon), and PANH (polycyclic aromatic nitrogen hydrocarbon). The main PAHs are naphthalene, fluorene, phenanthrene, and their alkylated homologs PASHs are benzothiophene and diben-zothiophene PANHs are indole, carbazole, quinoline, and their alkylated derivatives (see Table 1). 

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