A consumer group says it will sue the Consumer Product Safety Commission if it doesn't do something about what the group sees as the threat of cancer lurking in children's sand piles. A commission officials said Thursday there is no evidence that commercial play sand causes cancer, but the commission will make a formal decision on a petition to ban limestone products, including play sand, in September. Industry officials say if sand from the nation's rock quarries caused cancer, there would be higher instances of the disease among workers in the centuries-old industry. Public Citizen, a non-profit organization which fights for product safety and public health, said in a news release Thursday that many of the nation's children could be exposed to play sand that contains dangerous asbestos or asbestos-like tremolite fibers. ``During the hot summer of 1988 your children may be playing in the sandbox. Would you want them to be breathing asbestos as they pour buckets of sand over each other?'' the consumer group asked. Asbestos fibers have been proven to cause cancer when inhaled. Children who are exposed to them may not be afflicted until many years after exposure, the group said. In a letter to the product safety commission, Public Citizen said that if the agency does not indicate within 30 days that it plans to resolve the issue, the group will consider legal action. Appeals to the safety commission to protect workers and consumers from exposure to rock-based fibers date back 12 years. In May, the agency said it had evaluated several play sand samples and did not find asbestos in any of them. Public Citizen, however, said sand sold under two brand names, Basins Play Sand and Quickrete Kiddie's Fun Sand, have been shown by tests to contain tremolite, a rock-forming mineral that can occur in an asbestos form. ``No one knows how many other brands may be similarly contaminated,'' the group said. An official of Package Pavement of Stormville, N.Y., a distributor of Kiddie's Fun Sand, said five outside tests have been conducted on its sand and none found harmful ingredients. ``All indications are that there is no such fiber in our play sand,'' said Eileen Doherty, vice president for marketing. She said sand from a quarry in Connecticut does contain tremolite, but in a crystalline form which is not harmful. Sandra Eberle, safety commission program manager for chemical hazards, said no one has found true asbestos in play sand. She said the fiber-like particles that have raised concern are not tremolite asbestos but ultra-thin cleavages from crystalline tremolite that occur in some marble-based sand. ``It's very upsetting to us because parents get naturally terrified. I've spent a lot of time on the phone telling people this is not asbestos,'' she said. Ms. Eberle said, however, that the commission is still considering a petition by New Jersey geologist and physician Mark Germine to ban all limestone products, including play sand, lawn and garden limestone and consumer gravel products. Rick Renninger of the National Stone Association, which represents the industry, said the claim of cancer-causing ingredients in sand is old and is not backed up by the evidence. ``We produce a billion tons of stone a year in the United States, and we've been doing it for a couple of hundred years,'' he said. ``I think that there'd be evidence of asbestos disease problems in people exposed for their entire working lives, and there simply isn't.'' Renninger said tremolite is among the most common rock-forming minerals and is found in almost every rock product. Public Citizen researcher Dr. Lynn Silver, a pediatrician, accused sand distributors of trying to hide the danger of their products. ``The industry throws up a smokescreen,'' she said in an interview. ``If somebody dies from falling off the left side of a skyscraper, they tell you there's nothing to prove that falling off the right side is also dangerous.''