Polycyclic aromatic hydrocarbons (PAHs) are aromatic compounds with two or more fused benzene
rings in their structural configurations. PAHs do not contain heteroatoms and substituents on the ring system.
PAHs containing up to four rings are called light PAHs while those that contain more than four rings are considered
as heavy PAHs. Heavy PAHs are more stable and more toxic than the light PAHs. Generally, the increase in
the size and angularity of a PAH molecule results in an increase in hydrophobicity and electrochemical stability.
Ring linkage patterns in PAHs may occur in such a way that the tertiary carbon atoms are centers of two or three
interlinked rings. The examples of PAHs are naphthalene, anthracene, phenanthrene, acenaphthylene, acenaphthene,
fluorene, fluoranthene, pyrene, benz[a]anthracene, chrysene, benzo[b]fluoranthene, etc. PAHs can be produced
either naturally or anthropogenically and have toxic properties. Due to the health risk posed by their exposure,
there is a need to control the release of PAHs through air quality management. Refinery industries are required
to monitor and regulate their discharges. There is an urgent need for the considerable efforts to be applied
in the field of research to degrade and monitor potentially hazardous substances to control, predict and avoid
negative effects of PAHs pollution.