The toxic organic fluorine compound perfluorooctane sulfonate (PFOS) is causing an increasingly serious pollution problem in lakes and surrounding seas, including Tokyo Bay, a research group will show at a conference beginning Thursday in Sapporo.

While PFOS is soluble in water, it does not dissipate in the environment and is believed to cause reproductive defects and cancer, according to Nobuyoshi Yamashita, a senior researcher at the National Institute of Advanced Industrial Science and Technology.

However, in-depth studies on PFOS contamination in humans and the environment have not been done, and the central government has not demonstrated how it assesses the safety of the substance.

PFOS has long been used in a wide variety of industrial and consumer products, including fire-extinguishing foam and food wrappings.

The study by Yamashita's group indicates Tokyo Bay has the worst PFOS concentration, at 26 nanograms per liter of water, while the concentration is 12 nanograms in Osaka Bay, 9 nanograms in the Ariake Sea and 7.4 nanograms in Lake Biwa.

As for contamination in fish blood, bluegill in Lake Biwa have some 600 nanograms per 1 cc, the highest, while eels in Tokyo Bay have some 500 nanograms, according to the study.

The group is scheduled to present the results of its research at the Friday conference of the Japan Society for Analytical Chemistry, Yamashita said.

"We have found that PFOS contamination is spreading throughout Japan," he added. "We are planning to study how PFOS is absorbed in the bodies of living organisms."