Microplastics and PAH contamination in the Eastern Arabian Sea: A synergistic environmental hazard

How significant is the role of microplastics (MPs) in transporting toxic chemicals such as polycyclic aromatic hydrocarbons (PAHs) in marine ecosystems, particularly along India's vulnerable coastlines? Despite growing recognition of MPs as persistent pollutants and effective sorbents for hydrophobic compounds, limited evidence exists on their contaminant-loading potential in the Eastern Arabian Sea (EAS), a region subjected to intense anthropogenic stressors. This study quantifies PAHs associated with both pellets and fragments from 14 beaches in Maharashtra, Goa, and Karnataka along the EAS using column chromatography followed by Gas-chromatography mass spectroscopy techniques. The concentrations of ∑16PAHs in pellets were 1.9–29,500 ng/g (Goa), 0.6–22,900 ng/g (Mumbai), and 0.8–21,400 ng/g (Karnataka). For the fragments the ∑16PAHs ranged from 2 to 2,100 ng/g (Karnataka), followed by 1–1,500 ng/g (Goa) to 12–230 (Mumbai). 4–6 ring-PAHs dominated and the diagnostic ratios indicated combination of processes such as pyrolytic, petroleum spills, and combustion activities. The study also investigated which type of MPs, pellets or fragments, exhibited higher PAH concentrations, and explored the factors responsible. Pellets consistently exhibited higher PAH loads, likely due to their smaller size, greater surface area, and prolonged environmental exposure. The ecological risk associated with PAH-contaminated MPs showed that ∑PAH was higher than TEL (Threshold effect level) and ERL (Effects range low), indicating a probable occasional biological impact. On the other hand, lower ∑PAH level than PEL (Probable effect level) and ERM (Effects ranged median) suggest no significant adverse effects on marine or human ecosystems at the evaluated locations.