1.   Also present in the oil, and hence in the smoke from its combustion, were benzene and polycyclic aromatic hydrocarbons, both of which were carcinogenic.

2.   Organic compounds including a number of carcinogenic polycyclic aromatic hydrocarbons are also present in coal dust.

3.   Thames Water had the worst record for pesticides, as well as the biggest problem with polycyclic aromatic hydrocarbons, which are potentially carcinogenic.

4.   Natural gas is also virtually free of the lead, sulphur, particulates and aromatic hydrocarbons that cause pollution at street level.

5.   Among them are the polycyclic aromatic hydrocarbons, PAHs, which are known or suspected carcinogens.

6.   Aromatic hydrocarbons have been found in particles of interstellar dust, as well as in certain meteorites.

7.   Diesel tailpipe pollution contains a mix of arsenic, benzene, dioxins and PAHs, or polycyclic aromatic hydrocarbons, among other things.

8.   It also contained polycyclic aromatic hydrocarbons of the kind formed by barbecuing.