Pyrenes

Pyrene is a polycyclic aromatic hydrocarbon (PAH) consisting of four fused benzene rings, resulting in a flat aromatic system. The chemical formula is . This yellow-green solid is the smallest peri-fused PAH (one where the rings are fused through more than one face). Pyrene forms during incomplete combustion of organic compounds.

Pyranine is a hydrophilic, pH-sensitive fluorescent dye from the group of chemicals known as arylsulfonates. Pyranine is soluble in water and is used as a coloring agent, biological stain, optical detecting reagent, and pH indicator. Pyranine is also used in yellow highlighters to provide their characteristic fluorescence and bright yellow-green colour. It is also found in some types of soap.

Perhydropyrene is a hydrocarbon similar to pyrene. Single bonds with hydrogen replace the double bonds in the benzene rings.

1-Nitropyrene is a by-product of combustion and is the predominant nitrated polycyclic aromatic hydrocarbon (pyrene) emitted in a diesel engine. 1-Nitropyrene is listed as an IARC Group 2B carcinogen, indicating it is possibly carcinogenic to humans.