A group of researchers in Stockholm University in Sweden have found a new set of PAH materials in tyres, according to a paper published in the journal Environmental Science & Technology, published by American Chemical Society.

The paper shows that car tyres may be previously unknown potential source of carcinogenic dibenzopyrenes .

Eight tyres, purchased in the EU and manufactured between 2005-2006, were tested. They were analysed for 15 high molecular weight (HMW) polycyclic aromatic hydrocarbons (PAH), using pressurised fluid extraction.

The researchers said four dibenzopyrene isomers constituted less than 2 percent of the sum of the 15 analysed HMW PAHS.

These materials are not covered by the existing PAH ban, and the tyres were made prior to its existence.

 Roger Westerholm, one of the researchers told ERJ that it is "necessary to investigate what significance carbon black [and dibenzopyren] has to the PAH content. Further research is needed".