WASHINGTON (AP) -- The organic produce in the supermarket isn't grown with conventional pesticides, but chemicals can still show up on those fruits and vegetables, a consumer's group says.

A Consumers Union-led study of government data found pesticide residue on 23 percent of organic fruits and vegetables and on nearly 75 percent of conventionally grown produce.

None of the produce is unnecessarily unsafe. The residue seldom even approaches limits set by the Environmental Protection Agency.

"Less is better. Fewer residues and lower levels of residues are better than higher levels of residues and more residues," said Edward Groth, a senior scientist for Consumers Union, publisher of Consumer Reports.

The study is being published Wednesday in the journal Food Additives and Contaminants.

Much of the residue found in organic crops was of organochlorine pesticides, chemicals - including DDT and chlordane - that plants can soak up from the soil decades after the products were used. Other chemicals could have been applied to the crops improperly or drifted onto the organic fields from adjacent farms, the scientists said.

One sample of organic peaches contained 3.3 parts per million of the pesticide phosmet, suggesting the crop was sprayed shortly before harvest, the study said.

"It's very difficult to keep the food from contamination, ... but I still say organic is a good idea," said Rodrigo Hurtado, a Washington physician shopping Tuesday at a Fresh Fields supermarket. A sign in the store said organic foods were "grown without the use of synthetic pesticides, fungicides or fertilizers."

Organic crops account for just 2 percent of U.S. fruit and vegetable acreage, but the industry has been growing rapidly. Sales of organic foods reached $7.8 billion in 2000, a 20 percent increase from a year earlier, according to Packaged Facts, a market research firm.

The study was based on sampling by the Agriculture Department and the state of California as well as by the Consumers Union scientists. It did not take into account the many special pesticides approved for organic crops, including sulfur and bacteria sprays.

Those products are generally considered less toxic than pesticides used by conventional farms and government inspectors do not test for them. However, one natural pesticide used by organic farmers, pyrethrum, may cause cancer, and another is linked to destruction of nerves in rats. Both decompose quickly after being applied, but the study recommended more research on those pesticides.

"Consumers need to recognize that organic production doesn't mean pesticide-free production," said Carl Winter, a food toxicologist at the University of California, Davis.

"The best thing consumers can do is to eat large amounts of fruits and vegetables," he said. "Pesticides allow these to be produced in more abundant manner, making them more affordable and offering consumers greater variety."

Some scientists also have expressed misgivings about the occurrence of mycotoxins on organic produce as well as the use of manure as fertilizer, which could carry harmful bacteria if not prepared properly. Mycotoxins, substances produced by fungi, can be prevented with the use of conventional pesticides.

Agriculture Department data examined in the Consumers Union study showed residues on seven of 30 samples of organic fruit and 22 of 97 samples of organic vegetables, or 23 percent of the total organic produce tested. Nine of 19 samples of organic spinach four of 18 carrot samples had pesticide traces.

By comparison, pesticides were found on 73 percent of the 26,571 samples of conventional foods that were tested.

The tests also included some samples of "green-labeled" foods - fruits and vegetables sold with claims of reduced pesticide use. There were pesticide residues on about half the samples of those products. When the organochlorine chemicals were excluded from the analysis of organic foods, 13 percent tested positive for conventional pesticides.

"Consumers who seek to reduce their exposure to pesticide residues can do so reliably by choosing organic produce," the scientists wrote. "However, none of the choices available on the market is completely free of pesticide residues."

Copyright 2002 The Associated Press. All rights reserved.