What are polycyclic aromatic hydrocarbons (PAH)
Polycyclic aromatic hydrocarbons, also knows with the acronym PAH, are hydrocarbon compounds made by two or more aromatic rings - e.g. benzene - linked in a single, usually plane, structure. They are usually found in fossil coal and in oil, from which they are extracted mainly because of their aromatic-rich properties.
They are heavy atmospheric contaminants and their formation happens during incomplete combustion of fossil fuel, timber, fat, foliage, incense and organic compounds in general, such as those from urban waste. As such, polycyclic aromatic hydrocarbons may be found in waste fumes, biomass fumes, tobacco smoke and also in the smoke given off by cooked foods, more specifically in high temperature cooking, from grilling and barbequing to smoked fish production.
These contaminants are reason for great concern in that some of them were identified as carcinogenic, mutagens and teratogens. High molecular weight PAHs, such as benzopyrene and benzo[a]pyrene, are massively present in tar, bitumen, pitch and coal as well as any correlated products, including asphalt. Moreover, they may be produced by carbon black or wood fire soot and, in any case, they may be traced back to pyrogenic sources.
Light PAHs such as naphthalene and fluorene are contaminants that, given their higher solubility in water, may percolate and contaminate underground water reservoirs.
PAHs have many known negative effects on the environment, human and animal health, as well as evident toxicity against several water organisms and birds; they are highly chronically toxic for water life and highly contaminating for crops.
Several PAHs were classified by IARC (1987) as "likely" or "possible human carcinogenic elements", while benzo[a]pyrene was recently (2008) reassigned to group 1 as a "human carcinogenic element". Besides them other high PAH-content elements are among the proven human carcinogenic compounds.
To mention but a few of them, they are made to include tobacco smoke, carbon gasification processes, coke production and mineral tar distillation.
Benzo(a)pyrene, benzo(b)fluoranthene, benzo(k)fluoranthene, indeno-(1,2,3-c,d)pyrene, benzo(a)anthracene, benzo(j)fluoranthene and dibenz(a,h)anthracene are PAHs commonly found in environmental matrixes.
Even though there exist more than one hundred different PAHs, only some of them are believed to be most detrimental for human and animal health, more specifically: acenaphthene, acenaphthylene, anthracene, benzo(a)anthracene, dibenz(a,h)anthracene, crysene, pyrene, benzo[a]pyrene, indeno(1,2,3-c,d)pyrene, phenanthrene, fluoranthene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(g,h,i)perylene and fluorene.
The carcinogenic activity is due to the metabolic product of such substances, which are pre-mutagens.
How PAH forms in electric cable insulation layers
Even though they are not deliberately introduced in none of the materials commonly used to manufacture cable insulation and jackets, they may form in very small percentages and well below the regulatory thresholds, during the extrusion process because of overheating that may occur during isolate and undesired events, or even during the operation of the installed cables in case of overheating caused by a faulty or abnormal power flow. It follows that the attached statement does not rule out the possible presence of these compounds in very small quantities, though it does certify that their presence falls well below the allowed legal thresholds (as a general rule, in the region of fractions of ppm).
Sourced and adapted from Wikipedia.org
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