Saturday, March 23, 2019

Do You Really Need to Worry About Pesticides on Your Kale?

Bundle of Kale (Wikimedia commons)

Last week the Environmental Working Group (EWG) published its annual “Dirty Dozen List” and highlighted Kale near the top of it’s list of foods with “pesticide residue contamination.” They want you to buy your Kale as Organic.  EWG claims to base that recommendation on data from the USDA’s Pesticide Data Program (PDP), but a closer look at the actual data suggests a far different conclusion – that the Kale in our food supply is quite safe and that there is not the big difference between organic and conventional that they imply.

Since EWG gets much of its funding from large organic marketers, it is not surprising that their recommendation is to buy organic, but the 2017 PDP testing included 67 samples that were labeled as USDA organic (13% of the total for Kale).  Many of those organic samples had detectable residues representing 31 different chemicals, only one of which is approved for use on organic crops (Spinosad).

Now the levels at which chemicals were detected on the organic were very low and of no health concern based on the very conservative “tolerances” set by the EPA through its extensive risk assessment process.  However, the same can be said for the 455 conventional Kale samples tested the same year of.  The residues we are talking about here are hundreds to thousands of times below the relevant tolerance (see graph below).

In theory there wouldn’t be any synthetic residues on organic, but the USDA’s certification rule allows for “inadvertent” presence of synthetics at 5% or less of the EPA tolerance. (There is a separate USDA-Organic compliance testing program that looks for residues, and in that case the 5% rule applies).  98.9% of the 2017 PDP detections for organic Kale samples would meet that standard, but so do 98.1% of the residues on conventional samples.  Not so different, eh? In the graph above, only the red part of each bar would be a technical violation of the organic rules and none of the Kale detections for either conventional or organic exceeded the tolerance. Note that neither category is actually “dirty” based on a rational, scientific assessment.

Now, there were about three times as many residues/sample found on the conventional Kale, but the USDA does not even test for a great many of the pesticides that are approved for and regularly used on organic.  This would include “natural products” such as mineral-based materials (e.g. sulfur or copper compounds), petroleum oils, plant extracts, and biologicals).  Those sorts of products make up a substantial part of what gets applied to Kale. Thus, pesticides which are not part of the PDP testing make up 65% of the total pounds of crop protection agents applied to kale and 44% of the treatment acres (see graph below from the most recent available year of California use data).  Approval for organic is entirely based on what is considered to be “natural” and the USDA is quite clear that the classification is not about relative safety.

The acreage of Organic Kale has been increasing over the last 15 years and with it the use of the organic-allowed pesticides.  (See the example of sulfur use on Kale as linked to organic acreage in the graph below).

If the USDA tested for residues the natural product pesticides, the number of “detections” for organic samples would certainly increase. But as with the synthetics, the results would most likely indicate that this is a perfectly safe vegetable to consume whether or not it is organic.  Bottom line, the wisest thing for consumers to do is to ignore the fear-mongering of the EWG and simply enjoy a healthy diet including lots of this and other fruits and vegetables.