Polycyclic aromatic hydrocarbons from natural combustion processes

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]. 

Nitro-polycyclic aromatic hydrocarbons, referred to as nitro-aromatic compounds hereafter, constitute one of the most troubling classes of environmental pollutants. They are derivatives of polycyclic aromatic hydrocarbons (PAHs) that contain two or more fused aromatic rings made of carbon and hydrogen atoms and at least one nitro group (Fig. 10.1). Concern about these compounds arises partly from their ubiquity nitro-aromatic compounds are released to the environment directly from a variety of incomplete combustion processes [1] and are also formed in situ by atmospheric reactions of PAHs [2]. Nitro-aromatic compounds have been found in grilled food in diesel, gasoline, and wood-smoke emissions and are commonly found in atmospheric particulate matter, natural waters, and sediment [3-8],... 

Polycyclic aromatic hydrocarbons are generated from anthropogenic or natural combustion processes, in addition to rapid transformation processes of biogenic precursors that occur in situ. 

Polycyclic aromatic hydrocarbons (PAHs) are considered as priority pollutants due to their mutagenic and carcinogenic properties. PAHs are introduced in the environment from natural sources [e.g., incomplete combustion of organic matter from natural processes (volcanic eruptions, fires)] or anthropogenic, such as burning of fossil fuels, waste incineration, traffic, and so forth. 

A very different type of food toxicity involves toxins that are produced during the food preparation process. For example, charbroiled meats or smoked products (e.g., fish, sausage) typically contain polycyclic aromatic hydrocarbons (PAHs), formed during the cooking process (including barbecuing). Therefore, you will be exposed to small amounts of these chemicals when you eat meats that have been char-broiled. PAHs are naturally produced through combustion. They are also formed from forest fires, and are considered products of incomplete combustion. PAHs are also present in diesel fuels and car exhaust, and in smoke released from chimneys. 

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