Buying Organic on a Budget: Best and Worst Organic Produce

According to Environmental Working Group, here are the so-called 'Dirty Dozen' those twelve most heavily contaminated important types of produce to purchase organically when possible:
Apples
Celery
Strawberries
Peaches
Spinach
Nectarines- imported
Grapes- imported
Sweet Bell Pepper
Potatoes
Blueberries- domestic
Lettuce
Kale/Collard Greens

The 'Clean 15' listed below are the items that are produced with least contamination, therefore they are the safest conventionally grown produce.
Onions
Sweet Corn
Pineapples
Avocado
Sweet Peas
Mangoes
Eggplant
Cantaloupe- domestic
Kiwi
Cabbage
Watermelon
Sweet Potatoes
Grapefruit
Mushrooms

(Thanks to the Sanoviv Blog)