The Environmental Protection Agency announced yesterday that it was moving to ban all food uses of captan, a pesticide used since the 1950s to prevent fungal diseases in fruit and vegetable crops.

The agency, which has been reviewing captan's safety for five years, said it believed that the chemical posed "an unreasonable risk" of cancer to workers and to persons exposed to it through their diets.

However, the proposed ban would not take effect for at least two years.

According to EPA's risk estimates, cancer risks range as high as one in 1,000 for persons who eat foods containing captan residues for a lifetime. That would make the risks from captan nearly as high as those from ethylene dibromide (EDB), a grain fumigant that was banned for most uses last year when it was found to contaminate cake mixes, pancake flour and other foodstuffs.

EPA officials sought to play down the risk estimates for captan, contending that the figures are based on "worst-case" assumptions that may overstate the hazards of captan in food products.

Although captan has been under special review since 1980, the EPA has no reliable data on residues. To calculate cancer risks, the agency assumed that all foods treated with captan contain the highest residue level permitted by law and that none of the residue is removed by washing, peeling or cooking foods.

The agency said it intends to give captan's manufacturers, principally the Chevron Chemical Co. and Stauffer Chemical Co., two more years to gather information on actual residues.

The delay means that the EPA is not likely to take captan off the market until at least 1987.

"The potential risk from eating foods with captan are not immediate but are estimated from a lifetime exposure to the pesticide," said John A. Moore, head of the agency's pesticide division. "There is no present, acute danger to public health during the time we are taking to get residue data on foods."

About 10 million pounds of captan are used in the United States each year, much of it on strawberries, apples, almonds and stone fruits such as peaches, apricots and nectarines. Some home-garden products also contain captan, and the pesticide is registered for use on dozens of vegetables, from green beans to tomatoes.

The chemical also is used as a seed treatment on corn and soybeans and is widely found in such consumer products as wallpaper paste, textiles, oil-based paints, cosmetics and animal shampoos.

The agency said yesterday those nonfood uses would not be banned. Instead, the EPA is proposing to require protective clothing for persons who work with products containing captan, ranging from painters who apply oil-based paints to pet owners who wash their animals with captan-treated shampoos.

Canceling captan for food crops will cost users of the pesticide as much as $44 million, according to the EPA.

Alternatives to captan are available for most crops, but the agency said it was concerned that the ban "may encourage users to switch to other fungicides that may be more toxic than captan."

"Our data seem to indicate that fungicides as a class present toxicological problems," Moore said.