NO DOUBT existed several years ago that the 1953 Flammable Fabrics Act did little to protect citizens from death and injury by burning. About 300 children died annually in fires involving fabrics. Citizen pressure, hearings before the State Commerce Committee and burn statistics gathered by federal agencies led to new standards in 1972 and again in 1975, to make children's sleepwear flame retardant. Last week, the Consumer Product Safety Commission confirmed that a major failure has occured: One hazards, fire, has been replaced by another, the threat of cancer. As a result, the commission banned the marketing of the 40 per cent of all children's sleepwear that is treated with Tris, a chemical flame retardant. The Tris case illustrates a problem that will probably be with us for as long as new technologies continue to create new products - and new hazards.

The commission points out that, at the time manufacturers were asked to meet the flame-retardant regulations, the government had no authority to require federal pre-market testing of Tris. A hazardous substances act existed, but it stopped short of giving powers for pre-market testing of chemicals. That authority came later, with the recently passed Toxic Substances Control Act. Its jurisdiction belongs to the Environmental Protection Agency, not the Consumer Product Safety Commission.

This is a lot to ask the shopper at the sleepwear counter to have on his mind: three laws, several federal agencies and three sellers - the chemical makers, the garment manufacturers and the retailers. And that can be taken as only the beginning of the complexity: Although all children's sleepwear is flame retardant, the labeling doesn't say what chemicals a particular garment contains. A debate within the commission exists over washing Tris-treated garments; three members said last week that several washings reduce the risk, two members said that the evidence is weak for such a judgement.

The Environmental Defense Fund, the group that first prodded the commission, has taken legal action to require that retailers repurchase all Tris-treated sleepwear. Our own view on this matter is that retroactive payment is straining the point. The garment manufacturers acted in good faith, and the commission has attempted to deal with the breakdown honestly and openly.

The message from this case is that adequate protection from carcinogens has to e become an aggressively pursued goal of the federal government. As the public's confidence is shaken once again, those responsible for testing chemicals - in government and industry - have even more proof that both citizen safety and the industry's well-being are served if chemicals are thoroughly tested before they are marketed, rather than after.