Apples, celery and strawberries are at the top of the latest “Dirty Dozen” list compiled by the Environmental Working Group, while onions, sweet corn and pineapples are among the “Clean 15” fruits and vegetables the EWG says are least likely to carry pesticide residue.

In releasing the 2011 Shopper’s Guide to Pesticides in Produce, its seventh edition, the advocacy group emphasized that the health benefits of a diet abundant with fruits and vegetables outweigh the risk of pesticide exposure.

That observation wasn’t enough to prevent a withering reponse from the United Fresh Produce Association, which detests the regularly released lists. United Fresh blasted EWG for “misleading consumers” with “a sensational publicity stunt disguised as science,” that it claimed “will almost certainly discourage many people from eating the recommended amounts of fresh produce.”

Studies have linked pesticides to nervous system toxicity, cancer, hormone system disruption and IQ deficits. But there’s debate and uncertainty about the relative health risks of trace amounts of residue.

The EWG says it uses data from the U.S. Department of Agriculture’s annual reports on pesticides in food, and rates produce based on a composite score, equally weighing six factors that reflect how many pesticides were found in testing each type of produce and at what levels.  

It said “most samples were washed and peeled prior to being tested,” so the rankings reflect the amounts of chemicals that would likely be present on food when is it eaten.

USDA says in its latest report, released last month, that less than one-third of 1 percent of the food samples it tested contained pesticide residues exceeding the safe intake tolerances set by the Environmental Protection Agency.

Although about three percent of the foods USDA sampled contained pesticides for which the EPA hasn’t set standards, the department’s overall conclusion is that pesticide contamination of food is below the EPA limits.

United Fresh Produce Association president and CEO Tom Stenzel noted, in a prepared statement, that “If anything, the USDA data report, from which the Dirty Dozen is purportedly created, underscores the safety of fruits and vegetables.”

EWG said the latest USDA report showed that 98 percent of apples tested had at least one pesticide residue, which pushed apples up three spots from the last list, bumping celery from the top of the “Dirty Dozen.”  On the other hand, only 0.1 percent of fresh sweet corn had a detectable pesticide.

Cilantro made its debut in the new shopper’s guide. In testing the herb for the first time, USDA found 33 unapproved pesticides on 44 percent of the samples tested. EWG said that is the highest percentage of unapproved pesticides recorded on any guide item since the organization started analyzing the data in 1995.

For those fruits and vegetables listed as most likely to carry pesticide residues, the EWG suggests shoppers buy organically grown varieties.

Here are the EWG’s lists:

Dirty Dozen:  Apples, celery, strawberries, peaches, spinach, imported nectarines, imported grades, sweet bell peppers, potatoes, domestic blueberries, lettuce, kale/collard greens.

Clean 15: Onions, sweet corn, pineapples, avocado, asparagus, sweet peas, mangoes, eggplant, domestic cantaloupe, kiwi, cabbage, watermelon, sweet potatoes, grapefruit, mushrooms.