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.
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.
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.
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.
Aporte: Manuel Urrutia