Automotive polycyclic aromatic hydrocarbons (PAH)

The International Agency for Research on Cancer has classified certain PAH as carcinogenic to animals and probably carcinogenic to humans. Evidence for the carcinogenicity of some PAH is equivocal;for others there is no evidence of carcinogenic potential, and there are many others that have not even been tested. There is no common definition for the term ‘polycyclic aromatic hydrocarbon’. While in some scientific disciplines PAH are understood to be individual polycyclic aromatic hydrocarbons, in other areas the same term is used to define the total of all di- and tri+aromatic components determined in diesel fuel.

Even in this area there is still some conflict, for example, the Swedish diesel fuel specification uses the term PAH to refer only to tri+aromatics. Due to the concern about potential health effects the European Commission will propose an Air Quality Standard for PAH under a Daughter Directive under the EU Air Quality Assessment and Management Directive. The last CONCAWE Review outlined the complexity of the Daughter Directive for suspended particulate matter (PM10).

The issue for PAH is also very complex with contributions to ambient PAH coming from a range of different emission sources. This again necessitates experts from various scientific disciplines and industries working together. In this context it is worth noting that recent studies in various locations have demonstrated that the levels of PAH in current ambient air are the lowest ever measured largely as a result of the reduced use of coal in domestic and other heating.