n ever-increasing number of Americans are now opting for organic fruits and vegetables to reduce their families' exposure to potentially harmful pesticides. But organic produce can cost up to 50% more than conventionally grown, nonorganic produce and is not available in all markets.

Organic is the best choice if you are considering one of the 12 fruits and vegetables that are most heavily contaminated with pesticides when conventionally grown. Peaches, which are the most heavily contaminated, can contain up to nine pesticides per peach. By comparison, onions, which are the least contaminated with pesticides, contain no more than one pesticide per onion. (However, food-safety experts advise that the health benefits of eating produce -- organic or nonorganic -- outweigh the risks associated with pesticide exposure.)

But you don't have to buy organic all the time to reduce your exposure to pesticides.

THE HEALTH RISKS

For several years, studies have shown that pesticides, when given to animals, can cause a variety of adverse effects, such as birth defects, cancer and damage to the nervous system. When researchers at the National Cancer Institute and the National Institute for Environmental Health Science reviewed more than 300 studies (most of them epidemiologic -- research based on the health information of large numbers of people), they found links between pesticide exposure (agricultural, occupational or residential) and several types of cancer, including non-Hodgkin's lymphoma, leukemia and prostate cancer. Pesticide exposure also has been linked to a variety of problems affecting the nervous system, including headache, dizziness, depression, dementia, Parkinson's disease and Alzheimer's disease.

MEASURING TOXICITY

To help consumers choose produce wisely, scientists at the Environmental Working Group (EWG), a nonprofit environmental research organization based in Washington, DC, analyzed nearly 51,000 tests for pesticides conducted by the USDA and the FDA.

Every fruit and vegetable on the list received a score based on different measures of pesticide contamination, ranging from the percentage of samples that had detectable levels of pesticides to the total number of pesticides found.

The results of this analysis were used to rank the pesticide toxicity of 44 commonly eaten fruits and vegetables (mostly fresh) -- from the most heavily contaminated to the least contaminated. The resulting "Shopper's Guide to Pesticides in Produce" is available on the EWG Web site (www.foodnews.org).

BEST WAYS TO WASH PRODUCE

Washing fresh produce reduces levels of some pesticides, but it does not eliminate them.

The best washing practices, according to the FDA and other food-safety experts...

Use clean, cool running water. Do not use detergents, soaps or bleach to wash produce -- these may change the taste of produce and leave a residue. Store-bought sprays and washes used to clean vegetables and fruit are no more effective at removing pesticides than washing with plain water.

Scrub firm produce (such as apples or cucumbers) with a clean vegetable brush. For soft fruits and vegetables (such as grapes and tomatoes), gently rub them with your hands while washing.

Remove and discard the outer leaves of leafy vegetables (such as lettuce and cabbage) before washing. Thoroughly wash the other leaves under running water and shake off excess water.

Use a colander to wash berries and delicate greens (such as parsley and spinach). Gently spray the produce and drain it in the colander. Or, if you prefer, turn the produce as you hold it under running water.

Important: Peeling apples, radishes and other fruits and vegetables with skins helps reduce pesticide exposure, but some nutrients will be lost.

The Full List: 43 Fruits & Veggies

Note: We ranked a total of 43 different fruits and vegetables but grapes are listed twice because we looked at both domestic and imported samples.