A non-profit watchdog organization, the Environmental Working Group, has compiled a list of the 12 most heavily-pesticided fruits and vegetables which they call the dirty dozen. For example, when we eat a stalk of non-organically raised celery, we're taking in as many as 67 different pesticides. The foods on this list all have soft skins which makes them more likely to absorb the poisons they're sprayed with. They are:

1. Celery

2, Peaches

3. Strawberries

4. Apples

5. Domestic blueberries

6. Nectarines

7. Bell peppers

8. Spinach, kale and collard greens

9. Cherries

10. Potatoes

11. Imported grapes

12. Lettuce

When you buy these items, you should either pay the extra money for organic or avoid them altogether.

In addition to the dirty dozen, the EWG also lists the "clean 15" roster of non-organically-grown produce which is relatively safe to eat. Most of these have a thick outer layer which protects their insides from contamination.

1. Onions

2. Avocados

3. Sweet corn

4. Pineapples

5. Mango

6. Sweet peas

7. Asparagus

8. Kiwi fruit

9. Cabbage

10. Eggplant

11. Cantaloupe

12. Watermelon

13. Grapefruit

14. Sweet potatoes

15. Sweet onions

I've noticed that carrots, oranges, and bananas, which many people eat every day, are not on either list. I always buy organic carrots because they're thin-skinned, but I don't mind eating non-organic oranges and bananas because they're thick-skinned.