By Melinda Wenner Moyer for Slate
When my son was a baby, organic was a synonym for edible. If the apples I found at the grocery store weren’t certified, I wasn’t buying them. I knew that conventional produce could harbor traces of pesticides, and I’d read that pesticides could affect brain development. Sure, the details of this association were hazy -- I didn’t know how many pesticides my son might ingest from Shoprite strawberries, nor did I know whether that amount would do him any harm. But in a way, it didn’t matter: Shelling out a bit more cash to minimize the risks, whatever they were, seemed worth it to me.
Fast-forward two years and my son is eating Shoprite strawberries for breakfast. I support the principles of organic farming, for sure, but it can be hard to consistently pay $7 for a pint of something he’ll go through in two days. Plus, I can’t help but wonder whether giving my son organic food really makes a difference to his health, considering that he’s been known to lick the bottom of his shoes, kiss my poop-sniffing dog, and eat crackers -- someone else’s -- off of the preschool floor.
Instead of continuing to wonder, I decided to dig into the literature and talk to toxicologists, horticulturists, risk experts, and nutritionists to find out whether the chemicals in conventionally farmed foods could truly pose a risk to my child. What I’ve discovered has totally surprised me -- let’s just say I’m going to be a little more relaxed about what I serve kid No. 2.
I want to start off by saying that this column is not about whether organic agriculture is worth supporting for its environmental benefits (I think it is) or whether we as a society should care about the chemicals found in our foods and household products (I think we should). This column is about whether it’s worth buying organic produce for your kids specifically because you think the pesticides on conventional produce could harm them. (If you’re curious about the importance of feeding your kids organic dairy products, meats, and eggs, you’ll have to wait because I’m going to tackle that in another column.)
I’m also not going to spend much space addressing the recent debate over whether organic produce has higher concentrations of beneficial nutrients than conventionally-farmed produce does. James McWilliams already did a good job of discussing the nuances of that issue in Slate; from the research, it seems fairly clear that organic fruits and veggies don’t hold a major nutritional edge over conventional ones except in that they may contain fewer nitrates and more vitamin C, but there’s little evidence that these differences translate into actual health benefits. It’s also difficult to broadly compare the nutrients found in organically versus conventionally grown foods because geography and individual farm practices can impact growth drastically.
So let’s focus on that other major claim about organic food -- that is it’s healthier, particularly for kids, because it contains fewer pesticides. First, let’s start with the fact that organic does not mean pesticide-free. As scientist and writer Christie Wilcox explains in several eye-opening blog posts over at Scientific American, organic farmers can and often do use pesticides. The difference is that conventional farmers are allowed to use synthetic pesticides, whereas organic farmers are (mostly) limited to “natural” ones, chosen primarily because they break down easily in the environment and are less likely to pollute land and water. (I say “mostly” because several synthetic chemicals are approved for use in organic farming, too.)
The assumption, of course, is that these natural pesticides are safer than the synthetic ones. Many of them are, but there are some notable exceptions. Rotenone, a pesticide allowed in organic farming, is far more toxic by weight than many synthetic pesticides. The U.S Environmental Protection Agency sets exposure limits for the amount of a chemical that individuals (including kids) can be exposed to per day without any adverse effects. For Rotenone, the EPA has determined that people should be exposed to no more than 0.004 milligrams per kilogram of body weight per day. Let’s compare this toxicity to that of some commonly used synthetic pesticides, like the organophosphate pesticide Malathion. The non-profit Pesticide Action Network calls organophosphates “some of the most common and most toxic insecticides used today.” (Sarin, the nerve gas used in two Japanese terrorist attacks in the 1990s, is a potent organophosphate.) Yet the EPA has deemed it safe, based on animal tests, for humans to be exposed to 0.02 milligrams of Malathion per kilogram of body weight per day. This is five times more than the amount deemed safe for Rotenone. In other words, by weight, the natural pesticide Rotenone is considered five times more harmful than synthetic pesticide Malathion. The EPA’s recommended exposure limit for Glyphosate, another widely used synthetic pesticide -- you might know it as Round-Up -- is 0.1 milligrams per kilogram per day, which means it’s 25 times less toxic by weight than Rotenone. The synthetic pesticide Captan is 32.5 times less toxic than Rotenone, and another one, Pyrimethanil, is 42.5 times less toxic than Rotenone. Rotenone is also not the only natural pesticide that out-ranks synthetic pesticides in terms of toxicity. The pyrethrins, a class of pesticides derived from chrysanthemums that are approved for use in organic farming, are more toxic by weight than Round-Up, Captan, and Pyrimethanil, too.
It’s only fair to directly compare toxicities if people are being exposed to similar amounts of these synthetic and natural pesticides. Many organic farmers use pesticides as a last resort—so in theory, exposures to natural pesticides should be low. (Conventional growers don’t use pesticides unless they have to, either, though; spraying is expensive.) The problem is that farmers often “have to use a lot of the natural pesticides because they break down faster,” explains Linda Chalker-Scott, a professor of horticulture and landscape architecture at Washington State University. “One of the benefits of some of the more traditional synthetic pesticides is that they have been manufactured to be more effective at lower doses.”
Indeed, in a 1989 report, researchers at McGill University grew apples using either a mixture of organically approved natural pesticides, including a mixture of Rotenone and pyrethrins, or a synthetic pesticide called Imidan. They found that, using the natural pesticides, they could achieve a 75 percent yield on their apples only if they sprayed the fruit at least six to seven times throughout the growing season; using the synthetic pesticide, they could get a 90 percent yield with just four sprays. Another more recent study compared the efficacy of two natural pesticides to two synthetic pesticides and found the organic ones to be much less effective against aphids (plant lice) than the synthetic ones. Since organic farmers may have to spray crops more frequently with natural pesticides, it’s not crazy to think that organic produce could sometimes have just as much, if not more, pesticide on it -- natural pesticide, yes, but remember that natural isn’t intrinsically safe -- compared to conventional produce.
Ah, but what about all those studies that suggest that organic fruits and veggies harbor fewer pesticide residues than conventionally farmed produce does? Those studies only tested for synthetic pesticides. In the few studies that have also looked for natural pesticides -- the USDA’s Pesticide Data Program tested for them on organic lettuce in 2009, the California Department of Pesticide Regulation tested a handful of organic fruits and vegetables for certain natural and synthetic pesticides in 2010, and the USDA did an analysis of organic produce in 2010 -- scientists have found that between 15 and 43 percent of organic produce samples harbor measurable traces of either natural or synthetic pesticides or both. As far as I can tell, however, no one has published a comparison of the overall amounts of both types of pesticides on organic versus conventional produce, so it’s hard to conclude much from these findings other than that, yes, organic produce can be pesticide-tainted, too.
So now the question is: Are these pesticides harmful to your kids? As any toxicologist will tell you, it’s the dose that makes the poison. In other words, just because both conventional and organic produce are sometimes laced with pesticides doesn’t necessarily mean that they’re doing anyone any harm. And an analysis of the numbers suggests they’re not. In a 2011 study published in the Journal of Toxicology, Carl Winter, a pesticide and risk assessment specialist at the University of California-Davis, and his colleague Josh Katz took a close look at the fruits and vegetables that topped the Environmental Working Group’s “Dirty Dozen” list -- a top 12 list of what the non-profit group considers the most highly contaminated conventionally-grown fruits and vegetables sold in the United States. (This year, apples, strawberries, and grapes topped the list.) Winter was concerned that the EWG’s methodology was flawed; among other things, the non-profit group does not compare actual pesticide levels on fruits and vegetables to the EPA’s exposure limits to estimate true health effects of consumption.
To estimate how dangerous the pesticide exposures from the EWG’s “Dirty Dozen” actually are, Winter and his colleagues analyzed USDA data to determine the average levels of the 10 most commonly found pesticides on each of the 12 conventionally farmed fruits and veggies. They then used other USDA data to estimate the average amounts of each pesticide that individuals typically ingest from each of the 12 fruits and vegetables in a 24-hour period. Finally, they compared those daily exposure estimates to the EPA’s exposure limits for each pesticide.
What did they find? Well, let’s start with apples, which the EWG considers the most pesticide-laden fruit or vegetable out there, and look at the pesticide that is most commonly found on them, called Thiabendazole. Winter and his colleagues found that, each day from conventionally-grown apples and apple-based products, Americans typically consume a dose of Thiabendazole that is 787 times less than the EPA’s recommended exposure limit. Put another way, you’d have to eat as many apples and apple products as 787 Americans eat in a single day combined in order to be exposed to a level of this pesticide that approaches the EPA’s exposure limit.
For other fruits and vegetables, Winter and his colleagues found even less reason to worry. For Captan, the synthetic pesticide most commonly found on conventionally grown strawberries, Americans are exposed to 8,180 times less of the chemical per day than the EPA’s limit. Overall, Winter and his colleagues reported that the EPA’s exposure limits were more than 1000 times higher than the daily exposure estimates for 90 percent of the fruit and vegetable comparisons they made.
Granted, we’re exposed to pesticides through other means, too, and some pesticides may have cumulative effects -- but Winter says that even so, Americans won’t be ingesting anything close to the EPA’s limits for any of the pesticides used in U.S. agriculture. (And if you ever did ingest a pesticide at or above the EPA’s limit, you wouldn’t suddenly keel over and die. The agency sets pesticide limits at least 100 times lower than the lowest dose that caused any sign of harm, however minimal, to animals when they were fed that amount every day for most of their lives.) “We have a tremendous amount of data showing that what we’re exposed to in the diet for pesticides is very, very low, and certainly much lower than what would be required to have any even minimal health concern,” Winter says. And by the way, in none of these studies were the fruits and vegetables rinsed with tap water before they were tested, yet research suggests that doing so can reduce pesticide exposures significantly. Rubbing the food during rinsing helps, too.
In light of all this, what should we make of some of the research suggesting that kids exposed to pesticides are more likely to develop ADHD, lower IQs, and autism? Importantly, the latter two studies did not link pesticide exposure from food to these problems; what they found was that pregnant women who were exposed to high levels of pesticides, either occupationally or because they lived close to farms, were at an increased risk for giving birth to babies who went on to have lower IQs or develop autism. The study linking ADHD to pesticides is potentially more concerning: It found that kids ages 8 to 15 who had 10-fold higher concentrations of a pesticide break-down product in their urine had about 1.5 times the odds of having ADHD. It’s important to note, however, that the study only took a single urine measurement in the kids, so it’s hard to know whether it accurately reflected the children’s usual pesticide exposure or whether the day of testing could have been anomalous. Ideally, for a study like this, you want to track urine pesticide levels multiple times to make sure they’re consistent. One scientist critiqued the study because it did not control for the fact that ADHD often runs in families; if the researchers had done this, he argued, they probably would have found no association between pesticide exposure and ADHD. Finally, the ADHD study focused on the organophosphate pesticides, which are becoming less and less commonly used by U.S. farmers every year.
There’s another important thing to keep in mind about fruits and veggies: They are chock full of many naturally-occurring toxic compounds—things like flavonoids, hydrogen peroxide, and formaldehyde. Research conducted by Bruce Ames, director of the Nutrition & Metabolism Center at the Children’s Hospital Oakland Research Institute, has found that Americans consume about 1,500 milligrams of natural toxins from plants a day, which is approximately 16,000 times more than the 0.09 milligrams of synthetic pesticides we get from food every day. These natural toxins are for real, too: According to Ames’s work, the natural chemicals that are known to cause cancer in animals and are found in a single cup of coffee are about equal in weight to a year’s worth of our exposure to synthetic pesticide residues that are known to cause cancer. In a 1996 report, the National Research Council, a non-profit institution that provides expert advice to the government, noted that “natural components of the diet may prove to be of greater concern than synthetic components with respect to cancer risk,” in part because “synthetic chemicals are highly regulated while natural chemicals are not.”
If you ask Ames or the National Research Council what all this means, you won’t hear anyone say OMG don’t eat plants; they are trying to kill us. It’s Ames’s belief that plants are exceptionally good for us in spite of the fact that they contain high levels of natural toxins -- and that we certainly shouldn’t be worried about the minuscule differences in pesticide levels between organic and conventional foods. Indeed, if the research literature is clear about anything regarding fruits and vegetables, it’s that eating more of them -- conventional or organic -- does good things for the body. One review concluded that the quartile of Americans who eat the most fruits and vegetables, organic or not, are about half as likely to develop cancer compared to the quartile who eat the least. Fruits and veggies may also prevent heart disease and diabetes. A fascinating 2012 study used research-based models to predict what would happen if half of all Americans increased their (conventional) fruit and vegetable intake by a single serving each day; it predicted that doing so would prevent 20,000 cases of cancer a year. When the authors modeled whether this increased intake might pose risks due to the greater pesticide exposure, they concluded that yes, there might be 10 additional cases of cancer every year in the U.S. Put another way, the benefits far, far outweigh the risks.
What all this means for parents is that we should stop worrying so much about whether the apples we buy are organic or conventional -- we should just start giving our kids more apples. (And, sure, wash them when you can.) The Environmental Working Group agrees: In the first sentence of the executive summary of its 2013 Shoppers Guide to Produce, the organization points out that “the health benefits of a diet rich in fruits and vegetables outweigh the risks of pesticide exposure.” What’s more, irrational fears over conventionally farmed produce can introduce dangerous trade-offs. As University of Michigan decision psychologist Brian Zikmund-Fisher put it to me, “If you don’t feed your kid the ‘right strawberry,’ what do you feed him?” I’ve walked into markets with a hungry kid and been so afraid to buy the conventional apple that I’ve gotten him a snack pack of Annie’s Crackers instead. And I know there are parents who buy the Peter Rabbit Organics Fruit Pouches at Starbucks because they don’t know whether the bananas on display are organic. These aren’t smart moves. It is far, far better for your kids’ long-term health to get them in the habit of eating whole fruits and vegetables, regardless of what type of farm they came from, than to give them pretty much anything else to eat, no matter how organic or all-natural it may be.
In addition to the sources mentioned, The Kids would like to thank Jeff Gillman at Central Piedmont Community College.
Melinda Wenner Moyer is a science writer based in Cold Spring, N.Y. and is DoubleX’s parenting advice columnist. Follow her on Twitter.