When should you buy organic? We've addressed this question before with the previous Dirty Dozen but things change and so does pesticide use. The Dirty Dozen is a list of fruits, vegetables and other foods with the highest pesticide residue— and has just been updated for 2010. See what foods you really should consider buying organic, after the jump.

While a lucky few can afford to go 100% all the time, not everyone is so fortunate. There are times however, when it's worth splurging for that organic certification and times when it won't make as big an impact (in terms of pesticide residue). From The Daily Green, here's the most recent list of "dirty foods" as compiled by the Environmental Working Group:

The Dirty Dozen for 2010

1. Celery
2. Peaches
3. Strawberries
4. Apples
5. Blueberries
6. Nectarines
7. Bell Peppers
8. Spinach
9. Kale
10. Cherries
11. Potatoes
12. Grapes

The Clean 15:

1. Onions
2. Avocado
3. Sweet Corn
4. Pineapple
5. Mangoes
6. Sweet Peas
7. Asparagus
8. Kiwi
9. Cabbage
10. Eggplant
11. Cantaloupe
12. Watermelon
13. Grapefruit
14. Sweet Potato
15. Honeydew Melon

Click here for a handy reference card via the Environmental Work Group (PDF).

(Image: Flickr member celesteh's licensed under Creative Commons)