Summary - PAHs
Polycyclic aromatic hydrocarbons (PAHs) constitute a large class of organic compounds that are composed of two or more fused aromatic rings. They are primarily formed by incomplete combustion or pyrolysis of organic matter and during various industrial processes. PAHs generally occur in complex mixtures which may consist of hundreds of compounds.
Some PAHs are manufactured. These pure PAHs usually exist as colorless, white, or pale yellow-green solids. PAHs are found in coal tar, crude oil, creosote, and roofing tar. But a few are used in medicines or to make dyes, plastics and pesticides.
Humans are exposed to PAHs by various pathways. While for non-smokers the major route of exposure is consumption of food, for smokers the contribution from smoking may be significant. Food can be contamined by environmental sources, industrial food processing and from certain home cooking practices.
Eating grilled or charred meats, contaminated cereals, flour, bread, vegetables, fruits, meats, processed or pickled foods as well as drinking contaminated water or cow’s milk contribute to PAH exposure.
In a Scientific Opinion of the Panel on Contaminants in the Food Chain (CONTAM panel) by order of the European Food Safety Authority (EFSA) decided to include 15 +1 PAHs on the list of priority PAHs. These 15 PAHs, namely benzo(a)anthracene, benzo(b)fluoranthene, benzo(j)fluoranthene, benzo(k)fluoranthene, benzo[ghi]perylene, benzo(a)pyrene, chrysene, cyclopenta[cd]pyrene, dibenzo(a,h)anthracene, dibenzo(a,e)pyrene, dibenzo(a,h)pyrene, dibenzo(a,i)pyrene, dibenzo(a,l)pyrene, indeno[123-cd]pyrene and 5-methylchrysene, may be regarded as potentially genotoxic and carcinogenic to humans. Therefore, they represent a priority group in the risk assessment of long-term adverse health effect following dietary intake of PAHs. Based on the recommendations of the Joint FAO/WHO Expert Committee on Food Additives (JECFA) benzo(c)fluorene was included (Source: http://www.efsa.europa.eu/en/efsajournal/pub/724.htm)
The United States Environmental Protection Agency (EPA) has designated 32 PAH compounds as priority pollutants. The original 16 PAHs are naphthalene, acenaphthylene, acenaphthene, fluorine, phenanthrene, anthracene, fluoranthene, pyrene, benzo(a)anthracene, chrysene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene, dibenzo(ah)anthracene, benzo[ghi]perylene and indeno[1,2,3-cd]pyrene. This list of the 16 EPA priority PAHs (EPA-PAHs) is often targeted for measurement in environmental samples.
The structure of some of the priority PAHs is shown in Figure 1.
Figure 1. Structure of some priority PAHs.