Monitoring of environmental pollution caused by the heavy oil spill accident at the Japan sea and evaluation of toxicities of polluted environmental samples

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A Russian tanker Nakhodka met a hull-broken accident in sailing in the Sea of Japan on January 2, 1997, releasing a huge quantity of heavy oil into the Sea of Japan and the spilled oil polluted the coastline from the Shimane Prefecture through the Yamagata Prefecture. So, we conducted extensive scientific studies to assess where and how long the pollution by the oil or chemicals persist in the environment and the impact of the spill on biological systems. The following results were obtained in the present study: 1) The survey of oil-polluted area in Ishikawa Prefecture revealed that several area have been still heavily polluted with oil even at 2 years post-accident while number of polluted area has decreased in the course of years. 2) Many of the coasts polluted with oil located at the area steep and hard to get near and had surfaces covered with rocks or boulder / cobble / pebble / gravel. It has been considered that much effort to remove the reached oil was not made and natural cleaning effect with those areas was small. 3) As for polycyclic aromatic hydrocarbons (PAHs) in reached oils, concentrations of PAHs with 3-to 6-rings did not decrease significantly and were approximately half those of the oil loaded in the Nakhodka. 4) Indirect mutagenicities of reached oils sampled at 1 year post accident were approximately 80% of those sampled immediately after the accident and found to correspond to the PAH concentrations in reached oils. 5) Heavy oils including the Nakhodka-loaded oil were found to show antiestrogenicity and this activity was due in part to PAHs.