Polycyclic Aromatic Hydrocarbons
What are Polycyclic Aromatic Hydrocarbons (PAHs)?
Polycyclic Aromatic Hydrocarbons (PAHs) is an umbrella term for different hydrocarbon compounds, whose molecular structure consist of at least two interconnected benzene rings. PAHs occur as complex mixtures of more than a hundred different hydrocarbon compounds.
There are sixteen individual PAHs, which are usually used for analysis, representing the total group of substances. Examples of these sixteen PAHs are the carcinogenic Benzo[a]pyrene or Naphthalene.
Properties
PAHs are only very slightly soluble in water. As the number of condensed rings increases (or the size of the molecule), the PAHs become less volatile and less soluble.
There are numerous PAHs consisting of more than four benzene rings, which have shown to be carcinogenic for humans and animals.
Usage and applications
PAHs can be gaseous, dust-bound or even occur in a solid matrix. They result from incomplete combustion of organic material, such as coal, heating oil, fuel, wood or tobacco. They are bound to soot particles and are released into the air with them. Soot is often added to rubber materials, and consequently PAHs end up in rubber products, for example in shafts of tools, cable sheaths or even bathing shoes.
Considerable amounts of PAHs can also accumulate in foodstuffs, for example while processing grain products or vegetable oils, while cooking or smoking food over an open flame.
PAHs are natural components of coal and petroleum, and thus PAHs can also be found in secondary products resulting from the distillation of petroleum, such as asphalt, tar-containing adhesives, caulking materials, bituminous coatings or insulation materials like tar-containing cork boards.
Some typical applications of PAHs in buildings:
- Roofing felt
- Roofing tar
- Caulks/sealants
- Cork insulation
- Coatings
Risks
The three main exposure pathways to humans are via ingestion, inhalation and dermal absorption.
PAHs can cause irritation of mucous and inflammation of the respiratory system. There are many PAHs that are carcinogen to animals and humans. They can also be mutagenic and PAHs can cause damage to the immune system and be toxic to the liver. PAHs may have adverse effects to fertility and the reproductive system.
