Here's an article from the Healthy Happy Traveller: The dirty list of 12 fruits and vegetables with the most pesticide residue is called “The Dirty Dozen” and the other list of 15 with the least amount of pesticide residue is called the “The Clean 15″. Here it is

Dirty Dozen

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

Always purchase organic fruits and vegetables from the above list to avoid potentially harmful chemicals. Not sure if it is organic or not? Look at the sticker, if the number on the sticker starts with a 9, it is organic. If it starts with a 4, it is conventionally grown.

The Clean 15

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

The Clean 15 are grown with the fewest pesticides according to FoodNews.org. While it is not necessary to purchase the organic version of the Clean 15, remember to throughly wash all fruits and vegetables before eating. Also, the only way to avoid Genetically Modified produce is to purchase organic.