Environmental and Toxicological Health Impacts of Polycyclic Aromatic Hydrocarbons: A Review

Polycyclic aromatic hydrocarbons (PAHs) are globally significant environmental contaminants due to their persistence, resistance to degradation, widespread distribution, and potential for bioaccumulation. Their physicochemical properties, particularly hydrophobicity, thermal stability, and lipophilicity, facilitate long-range transport and bioaccumulation in environmental matrices and living organisms. PAHs originate from both natural and human driven sources, with emissions from industrial operations, fossil fuel, and residential activities being the most significant contributors. Many PAHs exhibit mutagenic, carcinogenic, and teratogenic, and endocrine-disrupting effects, thereby posing significant ecological and public health risks. PAH are broadly categorized into low molecular weight PAHs (LMW PAHs) and high molecular weight PAHs (HMW PAHs). Although extensive research has been conducted on LMW PAHs, evidence indicates that HMW PAHs, typically with molecular weight exceeding 300 Da, demonstrate greater environmental persistence, stronger bioaccumulative behaviour and severe long-term toxicological impacts. These effects are largely mediated through metabolic activation, oxidative stress induction, DNA damage, and aryl hydrocarbon receptor-dependent pathways. Despite these concerns, no HMW PAHs is included on the United State Environmental Protection Agency (US EPA) priority pollutants list, underscoring a critical gap in risk assessment and policy. This review critically evaluates recent advances (2018-2025) on the physicochemical properties, environmental distribution, exposure pathways, toxicological mechanisms, and associated health effects of PAHs. Key conclusions highlight the underestimated health risks regarding PAH mixtures, the importance of isomer-specific toxicity, and the enhanced hazard potential of alkylated and substituted PAHs. In addition, the effectiveness of contemporary remediation strategies, including bioremediation, phytoremediation, and advanced oxidation processes, is assessed, with integrated site-specific approaches identified as the most promising for the removal of persistent HMW PAHs. The review emphasizes the need for improved mechanistic studies and innovative risk management strategies to reduce human and ecological impacts.