White House consumer advocate Esther Peterson's first attempt at shaping administration policy under new powers given her recently by President Carter will focus on expert regulations on products with known risks to health or the environment.

Peterson is to meet today with representatives of more than a dozen federal departments and agencies to discuss export policy on such potentially hazardous products.

In a memo to the heads of the various agencies involved, Peterson said the decision to make this her first priority, was sparked by the recent controversy over the export of Tris-treated garments. Tris, a flame retardant, has been banned from use in the United States by the Consumer Product Safety Commission because it is believed to cause cancer.

Last month The Washington Post reported that manufacturers of children's sleepwear treated with Tris were selling the garments overseas at distress prices following the federal ban on the sale of Tris-treated clothes here.

The Consumer Product Safety Commission moved swiftly to halt those exports. In reversing a previous stand, the commission ruled that it had jurisdiction over any garments produced with the flame-retardant, including those for sale outside the United States, if they were first manufactured for domestic sale. All of the $50 million worth of clothes in question originally were manufactured for domestic sale.

The CPSC action triggered discussions at other federal agencies about the jurisdiction of exports of all regulated substances.

Sources at some of the agencies involved say that Peterson has chosen a tough subject for her first policy-making action.

"She may have a fight from the State department," said one source, "especially if she tries to come up with a policy giving agencies wide powers over export policies."