Apples and celery are still agriculture's dirtiest pieces of produce, according to the Environmental Working Group's annual "Dirty Dozen" report. The report names the fruits and vegetables ranking highest in pesticide residue.

Cucumbers were added to the 2012 Dirty Dozen, while Kale and collard greens were moved from the list to join green beans in a new "Plus" category.

The category was created this year to highlight crops that did not meet traditional Dirty Dozen criteria but are still commonly contaminated with organophosphate insecticides, which are toxic to the nervous system.

Also included on the Dirty Dozen list are:

1. Apples

2. Celery

3. Sweet bell peppers

4. Peaches

5. Strawberries

6. Imported nectarines

7. Grapes

8. Spinach

9. Lettuce

10. Cucumbers

11. Domestic blueberries

12. Potatoes

And on the "Dirty Dozen Plus" list:

+ Green beans

+ Kale/collard greens

The fruits and vegetables with the least amount of pesticide residue make up a list of the "Clean 15":

1. Onions

2. Sweet corn

3. Pineapples

4. Avocado

5. Cabbage