The Environmental Protection Agency has taken the first step toward regulating a chemical that is widely used to manufacture polyurethane plastics, calling it a "potential human carcino- gen."

The chemical is 4,4-methylene bis (2-chloraniline), commonly known as MBOCA. It is used as a curing agent in the manufacture of a variety of plastic products, including tires, gaskets, rubber shoe soles and skate wheels.

While the products are not believed to be hazardous, the process of manufacturing them presents "many opportunities for human exposure" to MBOCA, the EPA said. The chemical has caused cancerous tumors in laboratory rats, mice and dogs.

The chemical is not manufactured in the United States, but 1 million to 3.5 million pounds of it are imported each year for use in 200 to 400 plants around the country, according to the EPA. The agency has a range of options it could use to control the chemical, from banning it to requiring workers to wear protective clothing.

The agency said it would start a rule-making procedure, under a provision of the 1976 Toxic Substances Control Act that has been used only four times in the past, to issue rules on polychlorinated biphenyls, dioxin, fluorocarbons and asbestos.