PAHs (Polycyclic Aromatic Hydrocarbons) are mainly formed during incomplete combustion processes of organic materials and other pyrolytic processes. Only a minority of PAHs are industrially synthesized and serve as a basis for the chemical industry. PAHs consist of at least two condensed benzene rings. They are divided into low-molecular PAHs (2-3 rings) and higher molecular PAHs (4-6 rings). PAHs are predominantly neutral, non-polar solids and only very slightly soluble in water. With increasing number of condensed rings, volatility and solubility (also in organic solvents) decrease.
Of the several hundred known PAH compounds, 16 individual substances are of particular importance. These have been selected by the US-EPA (United States Environmental Protection Agency) as lead substances for environmental analytical investigations and are analysed, for example, in the field of contaminated site investigation and drinking water testing. Some PAHs (e.g. benzo[a]pyrene) are classified as mutagenic or carcinogenic compounds.
PAHs can be found, inter alia, in older asphalt pavements, parquet adhesives, tar and roofing felt, welded sheets, black paints and joint sealants, often in combination with chrysotile (white asbestos).
Parquet adhesive containing tar
Bituminous sheeting containing tar
Asphalt with high tar content
The group of polychlorinated biphenyls (PCB) comprises a total of 209 compounds. They were mainly used as plasticizers (jointing compounds), flame retardants (paints, varnishes) and insulating oils (transformer oils, capacitors, etc.). In the building industry, permanently elastic joint sealants, paints / varnishes on mineral material, wood or chipboard, coloured stone plasters, grouting and filling compounds and floor covering adhesives were frequent areas of application. The open application (sealants, paints) was prohibited in 1978. A general ban in Germany (also in transformers, capacitors, etc.) followed in 1989. PCBs are persistent, i.e. they accumulate in the environment and in organisms. They are also toxic and are suspected of being carcinogenic.
Acoustic ceiling panel type "Odenwald"
Wipe-resistant paint with PCB
Permanently elastic joint sealant in wall joint
PCP (pentachlorophenol) is classified as carcinogenic, mutagenic and toxic for reproduction. It was used for a long time in wood preservatives (HSM) (also indoors). Since 1978 there has been a labelling obligation and a ban on its use in indoor areas. PCP diffuses out of treated wood (= primary source) for a long time and thus leads to pollution of the indoor air, through which it then attaches itself to other organic materials such as house dust (= secondary source). PCP decomposes only very slowly. Therefore, in the case of remediation, possible secondary sources must always be considered in addition to the primary source.