Recently I was at a friend’s house for dinner with my family. I was chatting with my friend while she was putting dinner together, and while she was peeling the potatoes I remarked offhand that I never peel potatoes because I’m just lazy and it’s too much work. She said, “You’re going to think this is silly, but I’ve read lots of stuff about pesticides concentrating in the peel. Potatoes are on the dirty dozen list and I’m not sure how true that information is, but I feel like it’s a pretty easy way to avoid that. I even read that conventional potato farmers don’t eat their own potatoes, they grown a small organic plot for their families.” I said while I had never heard of pesticide residues concentrating in the peel, I seriously doubted potato farmers don’t eat their own crop. Based on the farmers I’ve met, my impression is that they’re extremely proud of what they do and likely they eat what they grow. But, I said I’d look in to it because I thought it was interesting. After slogging through lots of data and talking to some folks in the field, I’ve concluded you’re not really avoiding pesticides by peeling the potato, but you are reducing the nutritional value you gain from eating potatoes when you take the peel off.
Let me start by saying that this friend of mine is very smart. She used to be a science teacher and has a bachelor’s in microbiology and a master’s in immunology. I respect her quite a lot, which is why I decided to look into it. If a rational scientifically educated person accepts this, then average consumers with less science reasoning background likely will also. I did a google search, and I can see where she got that idea. The media loves to cover the Environmental Working Group’s “dirty dozen” list, and potatoes are tenth on the list. Just google, “do potato farmers eat their own potatoes” and you’ll see what I mean. The Dr. Oz show recently had Dr. Alan Greene on his show claiming he won’t eat conventional potatoes because of their high levels of pesticide residue. This NBC News article even says that farmers “pour on the chemicals” to ensure a harvest and that you can avoid pesticides by peeling. So how true is that?
I talked to a third-generation Washington potato farmer to find out about this idea that farmers don’t eat their own potatoes. This farmer certainly does. Not only do he and his family eat them, but they save them over the winter and eat them all year round. All of his employees also eat them, and he has family in other cities and states that beg him to bring potatoes when he visits. He even went so far as to say he doesn’t know any potato grower or any farmer that doesn’t eat his or her own produce. Does his family peel them? Sometimes, but that’s dictated by what dish his wife is making, not by concern over pesticide residues. (Clearly she’s not as lazy as me.) His farming operation applies pesticides to control pests (like fungus, insects, nematodes, soil borne disease, and weeds) that otherwise would damage his crop. If he didn’t use those pesticides, there would be fewer potatoes, the price would be higher, the quality would be lower, and the potatoes wouldn’t look very appealing.
He also told me that one misconception that really bothers him is that people who are unfamiliar with farming often think farmers spray pesticides just to be spraying pesticides. (Maybe because certain NBC articles say stuff like “farmers pour on the chemicals.”) “Spraying pesticide is expensive,” he told me. “The cost of an extra pesticide spray can make the difference between profit and loss on some fields.” Farmers aren’t just spraying crops willy-nilly. They’re spraying only when they have to because it costs money and time. That’s time those farmers could be spending with their families, so they’re surely not out there spraying for kicks.
While it seems to be true that some pesticides concentrate slightly more in the peel, that’s not the whole story. The dose makes the poison, right? When discussing pesticide residues, it is very important to distinguish between the mere existence of residue and how much residue is present. What people should really be interested in is: does the amount of pesticide residue on the potato pose a risk to my health? If there is 0.01 parts per million (ppm) of residue in the potato itself, but 0.02 ppm in the peel, that’s a higher concentration in the peel. But at such a low concentration, it’s unlikely to be a health risk (of course, the toxicity of the pesticide is important, too). The risk of injury present while driving to the store to buy potatoes is likely higher than ingesting that teeny tiny amount of pesticide residue.
I also dug a little deeper into the idea that the pesticides concentrate in the peel. I talked to a chemistry expert who told me that when tolerances are set for certain pesticides, the EPA also looks at what’s called a processed fraction, or a part of the commodity that might be different than the whole commodity (like the peel.) If a pesticide concentrates higher in a processed fraction than the commodity itself, there will be a different tolerance set for that fraction. (For a refresher on what tolerance means please see my primer article on how pesticides get approved.) So, I looked up on the EPA’s website how many of the pesticides that are approved for use on potatoes have a higher tolerance for the peel. Fourteen of the 121 pesticides listed had higher tolerances for the peel. That’s about 12 percent. It’s important to note here that those 121 pesticides have tolerances set for the commodity itself, which means that there are residues throughout the potato, so you’re not avoiding them altogether by peeling.
I also looked up the USDA’s data on potatoes from their Pesticide Data Program. The last time potatoes were sampled was in 2009. Of the pesticides analyzed, only three have higher tolerances in the peel. Importantly, of those three, none were found to be over the tolerance level for the commodity (which has a lower threshold), let alone the tolerance level for the peel. For example, Chlorpropham, also known as Bud Nip, was the most commonly found pesticide in samples, and it does concentrate higher in the peel. The residues found ranged from 0.010 ppm to 23 ppm, and the mean level found was 2.5 ppm. The tolerance for Chlorpropham is 30 ppm in the commodity and 40 ppm in the peel. Not one sample was over the tolerance level for the commodity, and the vast majority was far from it!
Side note: Chlorpropham is an important tool used to prolong the shelf life of potatoes. Those little sprouts that you sometimes find on potatoes when they’ve been in the pantry too long can be toxic when eaten in high doses. The use of Chlorpropham not only helps protect you from that, but it also significantly reduces food waste.
You’d have to eat a lot of potatoes to ingest enough pesticide residues to cause a problem. In fact, there’s a website called safefruitsandveggies.com that will actually do that calculation for you. I asked it to calculate how many servings of potatoes a child could eat in one day without any effect even if the potatoes have the highest pesticide residue recorded for potatoes. The answer: 6,494 servings of potatoes.
A serving of vegetables for a child is about half a cup. So that’s 3,247 cups of potatoes you’d have to feed your child in one day before you got close to a problem. And that’s assuming every single one of those potatoes were at the highest residue level ever recorded, which we know, from PDP data, that they aren’t. It is recommended that children have about one-and-a-half cups of vegetables per day, and the USDA tells us that children are not even getting those amounts. It would take a seriously concerted effort to get my kids to eat one and half cups of potatoes in one day, let alone 3,247 cups.
Can you really reduce your risk by peeling the potato? In short, I think the answer is that whatever miniscule benefits might be gained through peeling are likely offset by the loss in fiber and nutrients found in the peel. Twenty percent of the nutrients, and almost all the fiber, in a potato are in the peel. The residue in the peel is very small and far below tolerance; even so, most of the approved pesticides do not have a processed fraction tolerance, indicating they don’t accumulate more in the peel than in other parts of the potato. Most importantly to me, peeling the potato can’t substantially reduce a risk that isn’t there. Why is there virtually no risk? Because the amount of pesticide residue on potatoes (and produce in general) is so small that we can hardly measure it at all. That’s really more a testament to the sensitivity of the tests. The EPA and the USDA set rigorous guidelines for pesticide residues that are conservative and err on the side of being overly cautious for our safety. In practice, the residues aren’t even reaching these conservative limits.
I’m going to leave the peel on, which is good, because I’m lazy when it comes to cooking potatoes. Now I have a good excuse, though. I’m just trying to benefit from all those nutrients and fiber, I’m not lazy. That’s momsense.