Dirty dozen and Clean fifteen

When to buy organic? 

Consider this list that's been floating around the internet - I'm not sure of the original source.

The Dirty Dozen

1. Apples
2. Celery
3. Strawberries
4. Peaches
5. Spinach
6. Nectarines (imported)
7. Grapes (imported)
8. Sweet bell peppers
9. Potatoes
10. Blueberries
11. Lettuce
12. Kale/collard greens

The Clean 15

1. Onions
2. Corn
3. Pineapples
4. Avocado
5. Asparagus
6. Sweet peas
7. Mangoes
8. Eggplant
9. Cantaloupe (domestic)
10. Kiwi
11. Cabbage
12. Watermelon
13. Sweet potatoes
14. Grapefruit
15. Mushrooms