A chemical used to retard flames in children's sleepwear is a "potent" cancer-causing substance and garments that contain it should be banned from sale, the Environmental Defense Fund (EDF) said yesterday in a petition to the Consumer Product Safety Commission.

In tests conducted by the National Cancer Institute, EDF said, a high percentage of laboratory animals contracted cancers after eating the chemical, known technically as Tris (2, 3-dipromopropyl) phosphate and called "Tris" for short.

That data was obtained by EDF from the institute under the Freedom of Information Act and the interpretation of the data was EDF's alone. However, a spokesman of the cancer institute said yesterday "we have no reason to argue" with EDF's central findings. The cancer institute is preparing its own report on Tris.

Tris could be ingested by an infant mouthing the sleeve of his pajamas or absorbed through the skin, EDF scientists sad yesterday.

About 10 per cent of the sleepwear for the spring and summer season - or 5 million items - might contain Tris, said Fred Shippee, a spokesman for the American Apparel Manufacturers Association. "To the best of our knowledge," he said, "not a single yard" of Tris-treated fabric has been purchased by a manufacturer for the Fall 77 season.

He would not estimate how much Tris-treated sleepwear is currently in use.

Tris has been under suspision as a possible carcinogen (cancer-causing substance) for at least a year. During that time, its use in sleepwear has declined dramatically, according to several sources.

Velsicol Corp., which merged in January with Michigan Chemical Corp., the major manufacturer of Tris, announced last week that it was discontinuing Tris "for topical use" or application to fabrics. "Demand for Tris has declined," Velsicol spokesman Sander Allen said yesterday and constituted only $800,000 in 1976 of $169 million in sales.

In its petition yesterday, EDF asked that the Safety Commission look beyond Tris to the problem is a whole. "It makes no sense for the Commission to ban Tris while permitting it to be replaced by untested but chemically similar compounds which may pose a comparable health hazard to children" the petition said.

EDF chemist Robert Harris said yesterday that the Tris case "is the most outrageous example I've ever seen of in voluntary human exposure" to carcinogens.

EDF chemist Robert Harris said yesterday that the Tris case "is the most outrageous example I've ever seen of in voluntary human exposure" to carcinogens.

EDF has a petition pending with the commission asking for labeling on sleepwear containing Tris that would urge the consumer to wash the garment at least three times before using. Washing substantially reduces the levels of Tris that can be readily absorbed by the skin, Harris said.

The commission said yesterday it was waiting ofr the results of scientific testing by the Cancer Institute and others before requiring precautionary labeling. EDF's new petition will get "priority consideration" a Commission spokesman said.

At the moment, the consumer has no way of knowing if Tris has been used in the sleepwear, the EDF said. Certain febric types and blends, EDF said appear to meet flammability standards withoout containing chemical flame retardants. Those include Cordelan, Modacrylic (brand names include SEF, Kanecaron) and blends of Cordelan or Modacrylic with either polyester or nylon.

EDF and Harris were among the first to warn of possible carcinogens in the nation's public drinking water supplies. EDF is funded by foundation grants and private citizens and claims 40,000 members nationwide.