Polycyclic aromatic hydrocarbons (PAHs) are not easily degradable and exist as persistent contaminants in water environments. In this study we collected surface sediments and water samples from five different ports around Seto Inland Sea during October 2003 to April 2004. Fifteen PAHs were detected by gas chromatography/mass spectrometer (GC-MS). Expression of CYP1A enzymes was measured by a biochemical activation of 7-ethoxy resorufin ortho-deethylase (EROD). Total water PAHs ranged from 2.5ng/l to 132ng/l, while sediment PAHs ranged from 296.3ng/g to 3992.9ng/g, which indicate low to high level of PAH pollution. Selected isomer ratios (fluoranthene/pyrene to phenanthrene/anthracene and, total molecular weight of 202/total molecular weight 202–278), and detected PAHs suggested that the origin of pollution could mostly be pyrogenic. The highest total sediment PAHs were observed at the Uno Port while the lowest were at the New Okayama Port. EROD activity implied that PAH extracted from sediment samples affected on CYP1A enzymes expression on the human hepatocellular carcinoma cell line in a short exposure time (12 hours). Relatively EROD activity showed good correlation between PAH concentration and CYP1A expression for sediment samples. The highest EROD values were observed for sediment samples at a dose of 5ppm. In contrast water samples were at the low induction level even under the highest exposure concentration (50ppm), except in Mizushima Port. Biomonitoring of water environments by EROD activity could be a necessary tool for understanding the effects of PAHs on living organisms at the base of cell defense.

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