Blueberries and Kale Placed on Most Toxic List

Jun 02, 2010 | Updated Nov 17, 2011

The "dirty dozen" list of the 12 fruits and vegetables with the highest content of pesticides is published by the Environmental Working Group at their allied site For years I have been recommending that my patients, friends and family use this list to choose which foods they should purchase organically. If you like to eat any of the dirty dozen, then these are the foods you should be using your "organic food budget" money to purchase, rather than using it for foods that are not high in insecticide content (they also list the "clean 15").

The classics that have been on the list for the last decade are still on there: strawberries, peaches, apples, celery, bell peppers, spinach, cherries, imported grapes and potatoes. But this year, two new ones made it onto the list: blueberries and kale. Kale is the first of the brassica family (broccoli, cauliflower, cabbage, Brussels sprouts and kale) to hit the list. Many of its relatives have been on the "least toxic" list in the past, so this is quite surprising -- as is the presence of one of my most favorite foods on the list: blueberries.

But, what is the deal with blueberries?

The EWG's dirty dozen list is based upon the US Department of Agriculture (USDA) Pesticide Data Program. The most recent report, published in December of 2009, comprised all the data they had accumulated in 2008. It turns out that this was the first year that they had included blueberries in their study. This provides part of the explanation for its presence on the current list. However, I was really puzzled because I used to have blueberry bushes at my home in the Seattle area. I had four bushes that were over 75 years old, and they produced a lot of wonderful blueberries. Now, I did raise my entire garden organically, but I did not need to use any pest control on the blueberries with the sole exception of bird netting. So, I have been quite baffled by the addition of blueberries to the most toxic list, as pesticides shouldn't be necessary on them in the first place.

When I reviewed the Pesticide Data Program annual summary for 2008 I did find that the information was given by pesticide, not by food. So, there was no easy way to read all of the pesticide compounds that were found on blueberries. But, there was a table that gave basic information about many of the foods, including blueberries.

Here is what they said about blueberries:

They began with 726 samples of blueberries. Of those 726 they ran 166 analyses each for a total of 120,797 measurements (each for a different insecticide compound). Of those 120,797 tests 1,736 were positive and 119,061 were negative. They found a total of 46 different pesticide residues -- which is why blueberries made the list.

When I studied the report (by going through all the insecticides to see how the blueberries rated, I found that 17 out of those 46 pesticides were only found on less than one percent of all the blueberries tested. Another 14 of the 46 were found in less than nine percent of all blueberries tested, which means that 31 of the 46 pesticides that were found most likely drifted from other agricultural areas. Such infrequent contamination would have also been found on my backyard organic blueberries! Of the 46 insecticides found, seven were present in 15 percent or more of all samples with two fungicides found in over 30 percent. All but one of those seven commonly found compounds were fungicides, which makes much more sense for berry crops (but is still unnecessary). While I will still buy organic blueberries, I feel better knowing blueberries are not as toxic as I thought after reading the new list.

The other piece of good news that I found in this hunt was that frozen blueberries had less than half the number of insecticides present as the fresh berries. Since frozen blueberries deliver a much higher load of the health-giving berry pigments than fresh berries, this is the form that I typically recommend people consume.