Take an ordinary apple. By the time it reaches the fresh produce shelf, it has been dipped in fungicide, bathed in chlorine, scrubbed with detergent, and polished with wax.

"We do less to apples than anyone else does to other produce," says John Mandy, president of United Apple Sales in Clintonvale, N.Y. "What's natural in a store today? What hasn't had anything done to it?"

It seems as though the answer is not much.

A naturally green Florida orange, for example, is colored with ethylene gas and citrus red dye No. 2 -- after it's washed and coated with fungicide, and before it's waxed. Most potatoes are treated with a sprout inhibiting chemical so they can be stored for up to a year. And tomatoes, picked green, are treated with a ripening hormone for up to 72 hours before being shipped to market.

Government and industry officials say that the various postharvest chemicals applied to fresh produce are safe to eat. But consumer advocates question the use of additives that preserve or enhance the appearance of fruits and vegetables.

Serious questions have been raised about the safety of sulfiting agents, commonly used in salad bars, following the death in February of a 10-year-old Oregon girl who had eaten food treated with the chemical. Last year the fungicide ethylene dibromide, used for decades to keep insects and fungus out of stored grains, was banned after it was linked to cancer. But whether other substances are harmful is less clear.

"We don't know enough about the long-term and synergistic effects to give a clean bill of health to all postharvest chemicals," says Ellen Haas, director of Public Voice for Food and Health Policy in Washington, who believes additives pose a needless risk for consumers. "We've moved beyond the necessary use of postharvest chemicals to an overuse of them."

The use of waxes on fresh produce is widespread. And it's nothing new -- the Chinese fermented oranges and lemons by dipping them in molten wax during the 12th century.

Today, waxes are not limited to citrus fruits. The Department of Agriculture allows wax on apples, avocados, bananas, beets, cantaloupe, coconuts, cucumbers, eggplant, garlic, grapefruit, honeydew melons, lemons, limes, mangoes, muskmelons, onions, papayas, peapods, peppers, pineapples, plantains, pumpkins, rutabagas, squash, sweet potatoes, tangerines, tomatoes, turnips, watermelons and all nuts in shells.

The waxes, made from plant and petroleum sources, generally involve a mixture of carnauba, paraffin, polyethylene, shellac and synthetic resins. According to Dr. Corbin Miles, who is in charge of the Food and Drug Administration office that reviews such chemicals, the waxes are similar to those used for polishing floors and automobiles.

"Just because it's used on floors and cars doesn't mean it's unsafe for consumption by consumers in small amounts," says Miles.

Wax is also a good medium for applying fungicides, bactericides and substances that retard aging or ripening. Since wax has a high melting temperature, washing with hot water, contrary to popular belief, will not remove chemicals or wax. Nor will scrubbing with vinegar or deter-gent. Only peeling the skin, says Miles, will remove the wax.

While some industry officials maintain that waxing is done to protect the fruits from water lose and extend their shelf life, others contend that wax is used solely to enhance the appearance of the produce item.

"I think the claim that wax helps preserve tomatoes is mostly fallacy," says Wayne Hawkins, executive vice president of the Florida Tomato Exchange in Orlando, Fla. "Waxing is primarily cosmetic; it gives tomatoes a real sheen."

Many industry officials hold shoppers responsible for the waxing of fresh produce. "Eye appeal is so important -- people like big, red, shiny apples, that's all there is to it. You can't blame chain stores, it's consumer demand," says United Apples' John Mandy.

Florida orange growers, whose orange crop is naturally green, face a similar dilemma. A test marketing in Canada of uncolored Florida oranges more than 20 years ago proved these oranges were unable to compete with naturally orange-colored oranges from California and Israel. So, the Florida orange is colored with ethylene gas and citrus red dye No. 2. Although this dye has been linked to bladder cancer in some studies, the FDA permits the use of the dye in small and what it considers safe amounts.

The FDA requires that all growers and packers list waxes, chemicals and color additives used on fresh produce. Produce doesn't have to be individually marked, but the shipping crates must be labeled. Legally, this label information has to be displayed at all retail establishments.

Is it? "Not often," says Miles of the FDA. "But to be candid with you, it's not an area that we feel there's a big health problem or put a lot of resources into regulating. Most consumers know what they're buying. It's very obvious. As soon as you touch a rutabaga, you know it's waxed."

Michael Jacobson, director of Center for Science in the Public Interest, a Washington-based consumer group, believes that shoppers ought to be informed of chemical additives and that the FDA should enforce the label regulation. "Consumers have a right to know when foods are artificially colored, flavored or waxed," says Jacobson. "It's deception."

FDA officials are unsure whether it's the retailer or grower who is not passing along the label information.

Many retailers and some growers know nothing about the labeling regulation. "I haven't heard about it," says Dennis Chaisson of S.A. Chaisson & Sons Farm in Highland, N.Y. "I don't label my boxes that the apples are waxed, and I don't know any farmer around here who does."

Waxes are among the 450 substances on the FDA's "generally recognized as safe" (GRAS) list, which includes food additives in use before the Food, Drug and Cosmetic Act was passed in 1958. GRAS substances like caffeine and sulfites did not undergo the extensive testing of additives introduced after the enactment of the law. All GRAS substances have been under review since 1970. Since then, the FDA has either affirmed or restricted the use of 300 such food additives.

"We try to undertake a comprehensive, scientific review," says Miles. "But there's no absolute guarantee of safety."

Jacobson and other consumer advocates believe most GRAS chemicals, including waxes, are safe, but adds that changing the status of a potentially dangerous substance is diffiuclt. "In theory, it may be easy to shift an additive off GRAS, but in practice, industry fights every inch of the way with flocks of lawyers and scientists," says Jacobson.

Jacobson is currently engaged in a battle to ban sulfiting agents, which are put in foods including packaged mixes and wine, and sprayed on fresh items such as shellfish, mushrooms, grapes and salad ingredients. Sulfiting agents, used as a postharvest fungicide on grapes and to prevent fruits and vegetables served in restaurant salad bars from turning brown, have been linked to a dozen deaths and 500 other reported reactions, mostly among asthmatics.

Postharvest chemicals like sulfiting agents and waxes allow fresh fruits and vegetables to look better for longer. But how does this affect the nutritional value? "Usually the physical characteristics deteriorate at about the same rate as the nutritional value; if produce is wilted or doesn't look good, then it's value has gone down," says Joanne Daehler, coordinator of the Nutrition Information and Resource Center at Pennsylvania State University.

However, according to Haas, postharvest chemicals may conceal an item's age and, therefore, its nutritional content. An apple that's stored for 28 weeks loses 50 percent of its vitamin C, and an orange stored for 21 weeks loses 14 percent of its vitamin C.

"The real question is," says Dr. Melvin Johnson, chief of plant and protein technology at the FDA, "when does it cease to be maintaining food and when does it become deception?"