SEOUL, Jan. 18 Soil at 10 of 15 former U.S. military bases returned to South Korea are contaminated with high levels of toxic PCBs, a South Korean official said Thursday.Rep. Woo Won-shik of the governing Uri Party, and a member of the National Assembly's Environment and Labor Committee said the worst site was Colbern in Kyonggi Province, where the soil contains 44 times the acceptable level of polychlorinated biphenyls.Woo said as part of the transfer agreement, the United States had pledged to clean up all contamination, and he called for his government to renegotiate the deal, as it would cost Seoul $420 billion to decontaminate the sites, the Korea Times reported.Under a 2004 pact, the United States is required to hand over 59 bases to the South Korean government.The main source of the PCBs is electrical transformers. Exposure to the chemical causes severe skin lesions and liver damage, the report said.Copyright 2007 by UPI