Dibenzopyrenes are a group of high molecular weight

polycyclic aromatic hydrocarbon A Polycyclic aromatic hydrocarbon (PAH) is any member of a class of organic compounds that is composed of multiple fused aromatic rings. Most are produced by the incomplete combustion of organic matter— by engine exhaust fumes, tobacco, incine ...

s with the molecular formula C₂₄H₁₄. There are five

isomer In chemistry, isomers are molecules or polyatomic ions with identical molecular formula – that is, the same number of atoms of each element (chemistry), element – but distinct arrangements of atoms in space. ''Isomerism'' refers to the exi ...

s of dibenzopyrene which differ by the arrangement of

aromatic ring In organic chemistry, aromaticity is a chemical property describing the way in which a conjugated ring of unsaturated bonds, lone pairs, or empty orbitals exhibits a stabilization stronger than would be expected from conjugation alone. The e ...

s: dibenzo 'a'',''e''yrene, dibenzo 'a'',''h''yrene, dibenzo 'a'',''i''yrene, dibenzo 'a'',''l''yrene, and dibenzo 'e'',''l''yrene. Dibenzopyrenes have been recognized for their suspected human

carcinogenicity A carcinogen () is any agent that promotes the development of cancer. Carcinogens can include synthetic chemicals, naturally occurring substances, physical agents such as ionizing and non-ionizing radiation, and Biological agent, biologic agent ...

. The most notable dibenzopyrene isomer, dibenzo 'a'',''l''yrene is a constituent of

tobacco smoke Tobacco smoke is a sooty aerosol produced by the incomplete combustion of tobacco during the smoking of cigarettes and other tobacco products. Temperatures in burning cigarettes range from about 400 °C between puffs to about 900 °C ...

and is thought to be 30 to 100 times more potent as a carcinogen than benzo 'a''yrene. The four dibenzopyrene isomers; dibenzo 'a'',''e''yrene, dibenzo 'a'',''h''yrene, dibenzo 'a'',''i''yrene, dibenzo 'a'',''l''yrene are included in the list of 16 EU priority polycyclic aromatic hydrocarbons due to their

mutagenicity In genetics, a mutagen is a physical or chemical agent that permanently changes genetic material, usually DNA, in an organism and thus increases the frequency of mutations above the natural background level. As many mutations can cause cancer in ...

and suspected human carcinogenicity. Primary sources of dibenzopyrenes in the environment are combustion of wood and coal, gasoline and

diesel exhaust Diesel exhaust is the exhaust gas produced by a diesel engine, plus any contained particulates. Its composition may vary with the fuel type, rate of consumption or speed of engine operation (e.g., idling or at speed or under load), and whether ...

, and

tire A tire (North American English) or tyre (Commonwealth English) is a ring-shaped component that surrounds a Rim (wheel), wheel's rim to transfer a vehicle's load from the axle through the wheel to the ground and to provide Traction (engineeri ...

References

{{PAHs Polycyclic aromatic hydrocarbons Hexacyclic compounds