The Dirty Dozen
If your budget requires you to be selective about spending a little extra on organic foods, let the dirty dozen and clean fifteen guide your purchases.
Each year, the EWG, Environmental Working Group, updates the lists of most and least pesticide laden foods based on Department of Agriculture testing. These lists are not only helpful in guiding organic purchases but are informative regarding the changes in pesticide use in agriculture if you follow yearly.
Some of these pesticides are not specifically and directly harmful, but we are consuming them over a lifetime which has not specifically been tested. Some of the pesticides have been determined to be carcinogens, but are present within "acceptable" levels. And pesticides are not the only chemicals our produce is exposed to. Extremely toxic fumigants are used to sterilize growing soil to control pathogens when growing strawberries, potatoes, carrots, tomatoes, orchards, bell pepper, cantaloupe, and many other sensitive or high value crops. There are, of course, organic alternatives.
The dirty dozen list is compiled in order of contamination. It is recommended that you buy organic when purchasing these foods:
Sweet bell peppers
A thirteenth item was added for 2018, hot peppers, which they suggest to buy organic or cook conventionally grown peppers. If you are unable to buy these 13 items organically, at least rinse them well before eating to reduce consuming pesticides. Even better, soak in baking soda and water to further reduce pesticides.
Thoroughly washing produce with seemingly non permeable skin, such as apples, is no longer considered a good way to decide which produce to buy organically. Washing may not completely remove pesticide residue. And some pesticides are systemic so it enters and moves through the plant and can be found within the produce flesh. As for peeling pesticide exposed edible skins, the loss of nutrients is substantial if you don't eat the skin, somewhat negating the benefit of eating the produce.
If you must buy conventionally produced produce, these have been found to be least likely to contain pesticides:
Sweet frozen peas
Some organic foods are not much more expensive than conventionally produced foods, so start your purchases there and keep this lest in mind when prioritizing the rest of your organic budget.