In a report, the Basel Action Network (BAN), a nongovernmental organization, condemned the U.S. export of 13 aging naval ships — part of the so-called "ghost fleet."

The group said the first four of the former U.S. Navy supply ships had embarked for a demolition site in Teesside, northeast England, operated by Able U.K., with the 58-year-old Canistea and Caloosahatchee due to arrive in early November.

A U.S. court has blocked the export of the remaining nine vessels, said BAN, which monitors observance of the United Nations 1992 Basel Convention on cross-border movement of hazardous wastes.

The group said the sailing of the first four ships could set a precedent for the future export of U.S. vessels to other yards in Asia, where, environmentalists said, health and safety requirements were lower and the risk to workers more acute.

"But whether it's the U.K. or China, we should not be throwing our toxic trash on our global neighbors," Michael Childs of the environmental group Friends of the Earth said in a statement. "This export to the U.K. could give the Bush administration a terrible precedent ... to begin the wholesale dumping of this fleet of toxic ships on poor Asian communities."

The four rusting hulks contain more than 620 tons of asbestos, the group said in a statement, in addition to more than 470 tons of old fuel oil and 350 tons of polychlorinated biphenyls — a carcinogenic substance banned in the 1970s.

Able U.K. has said that all the ships had been drained of the more hazardous liquid PCBs ahead of their journey. It denies the vessels pose a risk and says they will be scrapped in a controlled and professional way.

BAN said it was irresponsible to tow the aging vessels across the open seas and risk them breaking up when they could be dismantled and made safe closer to home.

"Even if these floating time-bombs make it across the Atlantic and up the English Channel without mishap, there's a potential disaster waiting to happen in Teesside," organization official Jim Puckett said.