The Environmental Working Group just released their newest list of produce that is best to eat organic (dirty dozen), due to high levels of pesticides. The dirty dozen has added 2 veggies to its list making it a dirty dozen +2 (or a dirty bakers dozen +1, whichever you prefer). They also provide a list of the 15 cleanest foods. Take a look here to see where your favorite produce falls.
NOTE: there is a lot of controversy over organic vs. conventional produce. There are a few things to keep in mind when you are purchasing produce.
First, all of those pesticide studies related to subjects exposed before the 90s are studying a different kind of pesticide. Before the 90s almost all pesticides were fat-soluble (organophosphates). These were lower-dose pesticides, but they stay around for a long time. How? Anything that is fat-soluble can freely pass through cell walls and enter the body. Fat-soluble pesticide dissolved into the body and hangs out in cells for years. These can build-up quickly and cause major problems, because once it is in the cell there is really now way to get it out.
In the last 20-30 years there has been a shift from fat-soluble to water-soluble pesticides. The difference is that it is much harder for any of these water soluble pesticides to build-up in the body. Water soluble things cannot only cross into the body through special transporters. These transporters are pretty specific, so the likelihood of pesticides matching them just right is pretty low.
So this means you can eat all the pesticide containing food you want? Not really. Pesticide use isn’t tightly regulated, and with food coming from all over the world it is hard to know what has been used on your produce. It is safe to say water-soluble pesticides are safer than fat-soluble, but still hard to tell how much of any is safe to consume.
What do I recommend? Buy for a local, small farm. The reason why there is so much pesticide use is that large farms don’t have the manpower to manage pest control without tons of pesticides – spraying thousands of crops is much easier than spot-checking. Local farmers still use pesticides, but chances are they use less. In addition, you can get to know your local farmer and learn just what they do use on their crops. Not all produce needs to be organic in order to be low pesticide. Frequent your local farmers market to take control of your pesticide intake and help your local economy along the way.