A survey of about 30 businesses in Montgomery County last week showed that two stores were selling children's sleepwear treated with Tris, a flame-retardant chemical that is believed to cause cancer and sterility in humans, according to the county Office of Consumer Affairs.

"We found that about one-sixth of the sleepwear on sale at a Damascus store was almost surely Tris-treated. As soon as our investigators called this to the store's attention, it was removed from the shelves," said Barbara B. Gregg, head of the office.

She added that the Damascus store, a Ben Franklin Store, "apparently mislaid" a letter sent out by the headquarters of the chain listing types of nightwear that should not be sold and had never removed from sale all the Tris-treated night clothes on the list.

Scientists warned recently that Tris (Tris-BP), banned last year by the government from use in children's night clothes because it might cause cancer, has now been found to contain trace amounts of a pesticide that has been shown to cause sterility in humans.

Another Ben Franklin Store, this one in gaithersburg, was selling Tris-treated sleep garments last week because of an error in the list it received from the chain headquarters, said Gregg. "They (the store's management) had done what they thought was right, but they had not gotten all the Tris-treated garments off the shelves," she said.

Consumer office investigators checked the major chain stores and shops that specialize in children's wear, looking at labels in random samples of the sleepwear on sale, said Gregg.

"Store managers were aware of the problem and seemed to be doing all they could to take the Tris-treated garments off the shelves," she said. "On the other hand, there is still considerable confusion among the public" as to what kind of children's garments are considered safe, Gregg added.

The Consumer Products Safety Commission has said that synthetic fabrics known as modacrylic, matrix and vinyon, or blends of these fabrics are inherently flame retardant, and garments made from them do not require treatment with chemicals.

Biochemists Bruce N. Ames and Arlene Blum of the University of California at Berkeley, the scientists who warned of the new dangers from Tris-BP, said that a fire retardant some manufacuturers began using after the ban on Tris-BPis also a possible carcinogen. The chemical, Tris-CP, was not covered by last year's ban and has frequently been used to treat children's sleepwear made form 100 percent polyester.

Industry and consumer advocates differ on how mnay polyester garments treated with the tris-CP are still on sale in the United States.

An Environmental Defense Fund spokesman said that consumers who "really want to be safe" should avoid all 100 per cent polyester and buy only nightclothes made from the synthetic fabrics that are flame-retardant without chemical treatment.

Most Montgomery County stores are selling children's nightgowns and pyjamas made from 100 per cent polyester, but say that the garments are not treated with tris-CP, according to Gregg. The stores are relying on assurances from manufacturers that the garments are untreated, she said.

"There are also apparently some stores that still have garments (treated with Tris-BP) in storage," she said."We're trying to warn people to shop carefully because the garments could get back on the floor inadvertently."

Nightwear labels do not specify the types of chemicals used to make the garments flame resistant so shoppers have to know what kind of fabrics are treated with suspect chemicals. Acetate and triacetate, and blends of these two fabrics, are treated with Tris-BP. Cotton and nylon nightclothes are treated with chemicals other than the Tris solutions, according to the Consumer Products Safety Commission.