The Environmental Working Group (EWG) is a nonprofit group that ranks produce based on the level of measured pesticide contamination. Rankings are based on tests from the U.S. Department of Agriculture and the FDA, and a score given to each item in these six categories:
-Percentage of samples with detectable pesticide
-Percentage of samples with 2+ pesticides
-Average number of pesticides found in a single sample
-Average amount of all pesticides found
-Maximum number of pesticides in a single sample
-Total number of pesticides in the fruit or vegetable
The Dirty Dozen is a list created by the EWG that includes produce with the worst overall pesticide scores. For 2011, here is the Dirty Dozen list:
- Apples
- Celery
- Strawberries
- Peaches
- Spinach
- Nectarines (imported)
- Grapes (imported)
- Sweet bell peppers
- Potatoes
- Blueberries (domestic)
- Lettuce
- Kale/collard greens
- Onions
- Sweet corn
- Pineapples
- Avocados
- Asparagus
- Sweet peas
- Mangoes
- Eggplant
- Cantaloupe (domestic)
- Kiwi
- Cabbage
- Watermelon
- Sweet potatoes
- Grapefruit
- Mushrooms
Source: http://www.ewg.org/foodnews/methodology/