An apple a day may not keep the doctor away, especially if that Granny Smith is not organically grown, according to the latest report published by the Environmental Working Group (EWG).

In its 2011 annual report, the EWG updated its list of the fruits and vegetables with the most and least amount of pesticides. The resulting “Dirty Dozen” and “Clean 15” ranks 53 fruits and vegetables using data published by the USDA and FDA.

The Dirty Dozen includes produce that is most heavily sprayed with pesticides. While last year celery topped the list, this year, apples moved into first position. That’s because 98 percent of apples in the U.S. have some pesticide residue, even after being washed in water.

In addition to apples, other fruits and vegetables on the Dirty Dozen list include strawberries, peaches, nectarines, grapes, blueberries and sweet Bell peppers. On the other end of the spectrum, are those fruits and vegetables that are the least pesticide laden including favorites like corn, cantaloupe, watermelon and sweet potatoes.

In compiling the rankings, the EWG tested produce after washing and peeling. Rankings reflect the amounts of chemicals present on the food when eaten. An overall score is calculated using six different measures:

• Percent of samples tested with detectable pesticides
• Percent of samples with two or more pesticides
• Average number of pesticides found on a single sample
• Average amount (level in parts per million) of all pesticides found
• Maximum number of pesticides found on a single sample
• Total number of pesticides found on the commodity

For those interested in learning more about the pesticides on produce, the Pesticide Action Network has compiled a great website, What’s on My Food. It is a searchable database designed to make the public problem of pesticide exposure visible and more understandable.

In using the database, we found that apples contain 42 pesticide residues including 7 known or probably carcinogens, 19 suspected hormone disruptors, 10 neurotoxins and 6 developmental or reproductive toxins. This doesn’t include the 17 found that are known to be honeybee toxins.

We know that many of the chemicals used in pesticides are harmful to humans. Pesticides are known to be toxic to the nervous system, cause cancer and disrupt hormones. Of particular concern is exposing these chemicals to young children during the critical stages of their development.

How much pesticide exposure is too much is not well understood and depends on the pesticide, the person, timing and type of exposure. Unfortunately, pesticide regulation in the U.S. does not adequately account for things like additive and synergistic effects. Importantly, the harm of consuming low doses on fruits and vegetables over the long-term is not known. Clearly, more research is needed in this area.

Armed with this information, should you avoid eating fruits and vegetables? No, say health experts. According to EWG calculations, you can lower your pesticide intake by 92% if you avoid the dirty dozen. Alternatively, by purchasing organic fruits and vegetables, you can avoid these harmful chemicals altogether.

Ken Cook, the president and founder of EWG says, “We recommend that people eat healthy by eating more fruits and vegetables, whether conventional or organic.”

The Bottom Line

Having grown up with a large vegetable garden and orchard, I know firsthand the difficulty in warding off pests, fungus and insects. But, using pesticides on a wide scale basis over the long-term is worrisome.

My recommendation is to continue to eat plenty of fruits and vegetables. This summer, try to buy from a local farmer’s market, keeping in mind that their produce may be fresher but not necessarily organic. Or, plant some tomatoes, bell peppers or other vegetables that grow easily in a pot.

When grocery shopping, take note of the Dirty Dozen list and try to buy organic if you can. Keep in mind that whatever type of produce you purchase – conventional or organic – you must wash before using. And, even if you wash conventionally grown produce with a fruit wash or remove the peel, most likely some pesticide residue will remain because they’re taken up by the entire plant.