(This post was originally a response to someone asking whether cooking non organic potatoes reduced the amount of pesticide residue. I decided to post my answer here)
Okay, so we’d all probably prefer to buy organic all the time, but it’s certainly not the cheaper option. So let’s say you decide to buy some conventionally grown potatoes, with all the potential lovely chemicals. You of course have to cook the potato to eat it (if anyone out there actually eats raw potatoes, let me know, because that’s weird), so does cooking it make the whole pesticide residue issue less of an issue? Let’s take a look.
I found this great website which lists the common pesticides found on conventional potatoes: http://www.whatsonmyfood.org/food.jsp?food=PO
Apparently the most common potato pesticide is chlorpropham. And while studies tend to show the risks of chlorpropham in the amount consumed in food are probably low (1), it never hurts to play it safe. Cooking potatoes reduces chlorpropham a little bit (2,3), but since most of the chloropropham in potatoes is found in the peel, peeling potatoes reduces it the most (4).
Imidacloprid is next. While it again doesn’t appear imidacloprid is a huge risk in the amounts found in foods (5), I’m much more wary of it than chlorpropham. One study found that washing tomatoes reduced Imidocloprid by about 66% (6). Another study found that washing and cooking various vegetables (none of them potatoes) greatly reduced imidacloprid (7). Finally, another study on mallow found that boiling mallow significantly reduced imidacloprid, with much of the pesticide potentially being transferred into the water (8). Once again, a greater amount of imidacloprid is likely found in the peel (9).
Azoxystrobin is fungacide also apparently common in potatoes. Again, doesn’t appear to be super bad (10), but I still wouldn’t want to eat it. One study found cooking zucchini reduced azoxystrobin a little bit (11). Interestingly, the book “Pesticide Residues in Food and Drinking Water: Human Exposure and Risks” claims that photolysis is a mjor means of azoxystrobin degradation, meaning sun exposure reduces the fungacide.
Okay, we’ve looked at the more common pesticides, but what about the dangerous ones? O-phenylphenol is a bad one in my opinion. Cooking fruit has been shown to degrade it a bit (12). Also, since O-phenylphenol is often added after the plant has grown to prevent spoiling during transport I’m willing to bet the potato peel often houses much of the chemical.
Boscalid: boiling spinach has been shown to reduce boscalid (13). Washing, peeling, and cooking carrots reduces baoscalid significantly (14).
Thiobenzadole does not appear to be reduced much by cooking (15,16). Some studies have reported that thiobenzadole has a greater affinity for the skin and gets partitioned there at a greater rate (17). So peeling potatoes will likely remove much of the thiobenzadole (18).
Studies on meat have found that cooking may reduce many of the nasty organochlorine pesticides (19,20). One study on potatoes found the same thing and added “acidic solutions were more effective than neutral and alkaline solutions in the elimination of the organochlorine compounds under investigation” (21). So perhaps add some vinegar or lemon juice to the boiling water you cook with? This same study found cooking also reduced organophosphates in potatoes as well.
Organic potatoes will certainly be better. But if you do buy conventional potatoes, I think peeling them and boiling them will go a long way in reducing possible pesticides (22). It’s something to keep that in mind when you see vegetables that you commonly cook (like the potato) on pesticide measuring “dirty dozen” lists alongside fruits that you rarely cook.