Distribution and potential carcinogenicity of polycyclic aromatic hydrocarbons in beached and pelagic tarballs along the eastern Arabian Sea.

Abstract

Tarballs, the weathered residues of petroleum hydrocarbons, are a recurring feature along the west coast of India, yet their role as carriers of toxic and carcinogenic compounds remains insufficiently quantified. This study presents a comprehensive assessment of the distribution, composition, abundance and carcinogenic potential of polycyclic aromatic hydrocarbons (PAHs) in pelagic and beached tarballs collected along the Eastern Arabian Sea and the adjacent coastal regions (2018-2024). Results indicate that both pelagic and beached tarballs are dominated by low and medium-molecular-weight(LMW) PAHs, with phenanthrene consistently identified as the most abundant compound. Total PAH concentrations were markedly higher in pelagic tarballs than in beached tarballs. Diagnostic PAH ratios and principal component analysis suggest that the observed differences in PAH composition between pelagic and beached tarballs are consistent with the effects of environmental weathering. Assessment based on benzo[a]pyrene toxic equivalents (BaP-TEQ) and carcinogenic PAH fraction (cPAH%) indicates higher carcinogenic potential in pelagic tarballs, whereas beached tarballs exhibited greater spatial variability in PAH composition. Despite evidence of weathering, carcinogenic PAHs persisted in both tarball types, with some locations exhibiting notably elevated contributions. Overall, the study demonstrates that pelagic tarballs function as mobile vectors of carcinogenic hydrocarbons in the marine environment, while beached tarballs act as persistent secondary sources of contamination.. These findings highlight the potential environmental concern associated with tarball-derived PAHs and underscore the need for sustained monitoring and management of petroleum residues along coastal ecosystems.