IMO (International Maritime Organization) recognized that chronic exposure to benzene vapor in air may cause leukemia even if the concentration is very low, such as a few parts per million. Tankers in Japan, however, transport various kinds of chemicals over 15 (MT/year). Not only benzene but also other chemicals transported by marine vessels have adverse effects to the human health condition. Considering this background, we conducted field measurements of benzene, xylene, toluene, styrene and acrylonitrile to grasp the pollution level on the chemical tankers. The measurement clarified both the working environmental concentration and the exposure concentration of tanker crew.