PAH pollution in water and blue mussels (Mytilus edulis) along the northern Portuguese Atlantic Coast: Evaluation of ecological and human cancer risks

Coastal areas adjacent to urban and industrial regions are vulnerable to pollution from polycyclic aromatic hydrocarbons (PAHs), posing potential risks to both ecosystems and human health. This study quantified 16 priority PAHs in seawater and blue mussels (Mytilus edulis) from four beaches along Portugal's northwest coast over two years for seawater samples and four years for mussel samples. PAHs were measured in the dissolved aqueous phase (DAP), suspended particulate matter (SPM), and mussels using gas chromatography-mass spectrometry (GC-MS). Mean concentrations were 13.3 ng/L (DAP), 134.0 μg/kg dw (SPM) and 136.9 μg/kg ww (mussels). Source identification indicated both pyrogenic (wildfires) and petrogenic (maritime activity) inputs. Toxicity assessment revealed low carcinogenic potential in DAP (TEQ ≈ 0.7 ng/L) and moderate risk in SPM (TEQ ≈ 6 μg/kg dw). Risk coefficients classified DAP as low risk and SPM as moderate risk. In mussels, although the hazard index values were below 1, the estimated lifetime cancer risk (≈ 2.5E-05) exceeded the EU safety threshold of 1.0E-06, indicating a potential carcinogenic risk from human consumption. These findings emphasize the necessity for continuous monitoring and more robust regulatory measures to manage PAH contamination in coastal environments, thereby mitigating associated ecological and public health risks.