REVIEW PAPER Biogeochemical Cycle, Occurrence and Biological Treatments of Polycyclic Aromatic Hydrocarbons (PAHs) Aqib Hassan Ali Khan 1 • Muhammad Ayaz 1 • Maryem Arshad 1 • Sohail Yousaf 1 • Muhammad Abeer Khan 3 • Mariam Anees 2 • Aneesa Sultan 2 • Ismat Nawaz 4 • Mazhar Iqbal 1 Received: 29 March 2017 / Accepted: 24 November 2017 Ó Shiraz University 2017 Abstract Polycyclic aromatic hydrocarbons are responsible for contaminating environmental compartments around the world, imposing risk associated with human health and ecosystem pollution. Emissions from anthropogenic activities predomi- nate; nevertheless, open burning, volcanic activities, and natural losses of petroleum deposits are prominent natural sources. Different physical and chemical treatment technologies have been developed and tested for the removal of PAHs, but the use of biological entities was found most favourable for adaptation at industrial scale. This review can help to understand the mobility of PAHs in the environment. Focus of this review is on identifying processes through which PAHs are added to environment, their biogeochemical cycles, biodegradation, environmental and substrate-specific factors affecting biodegradation. Further studies related to different bioprocesses linked with remediation and removal method- ologies along with factors affecting the treatment have also been brought into consideration. This review brings together inter-disciplinary aspects and understanding for PAHs, to which no previous review has focused. Keywords Abiotic factors Á Biodegradation Á Biogeochemistry Á Biotic factors Á PAHs Á Toxicity 1 Introduction Combustion of different masses and incomplete pyroly- sis of oil, petrol, diesel, wood and coal result in the formation of organic contaminates, among which poly- cyclic aromatic hydrocarbons (PAHs) are found in almost every environmental compartment (Halsall et al. 2001). Physico-chemical properties of PAHs predict their residence and behaviour in environment. More volatility and higher solubility were observed for 2 and 3 ring PAHs, when compared to PAHs having three or more rings. The first group is present more frequently in vapour phase, while the later bind more commonly with particulate matter. With about 30 PAHs and 100 of its derivatives being identified, out of which many have mutagenic and carcinogenic effects, PAHs represent leading class of chemical compounds capable of causing cancer (IARC 1987). Heavy quantities of PAHs occur near the vicinity of their emission source (Halsall et al. 2001). PAHs are rapidly transported from their primary source and cause severe human health impacts (Menzie et al. 1992). This review focuses on PAHs biogeo- chemical cycles, ways through which contamination occurs and associated toxicity. Further recent studies, related to different bioprocesses linked with remediation and removal methodologies along with factors affecting the treatment, have also been brought into consideration. This review brings together inter-disciplinary aspects and understanding for PAHs, to which no previous review has focused. & Mazhar Iqbal mazz366@yahoo.com; miqbal@qau.edu.pk 1 Department of Environmental Sciences, Faculty of Biological Sciences, Quaid-i-Azam University, Islamabad 45320, Pakistan 2 Department of Biochemistry, Faculty of Biological Sciences, Quaid-i-Azam University, Islamabad, Pakistan 3 Institute of Environmental Studies, University of Karachi, Karachi, Pakistan 4 Department of Environmental Sciences, COMSATS IIT, Abbottabad, Pakistan 123 Iran J Sci Technol Trans Sci https://doi.org/10.1007/s40995-017-0393-8