Nonorganic Foods Have Pesticide Residue—but Is It Bad for You?

Researchers are finally trying to figure out if long-term, low-level exposure to agriculture chemicals presents a health risk.

Nonorganic Foods Have Pesticide Residue—but Is It Bad for You?

MAR 14, 2016

Heather Rogers has written for ProPublica, The New York Times Magazine, and Mother Jones. Her most recent book, Green Gone Wrong, explores the contradictions of green consumerism. She lives in Brooklyn, New York.

Researchers are finally trying to figure out if long-term, low-level exposure to agriculture chemicals presents a health risk.On a recent snowy February morning, Melissa Green strolled through the grocery aisles with her family at a Whole Foods in Brooklyn, New York. Her husband, Mike O’Hagan, palmed a package of organic crackers and tossed it into the shopping cart. Their son, Marlowe, just shy of two years old, was perched in the cart’s kid seat. He turned around to reach his hand down toward the oranges, blueberries, and applesauce in the basket, all of it organic.

For the last decade, the couple said, they’ve paid close attention to what they eat. But that picked up when Green got pregnant and has continued since Marlowe was born. “I see it as my duty to give him the best start,” she said, steering the cart toward the dairy section. What motivates her family to avoid conventionally raised food? “It’s one way to minimize toxins, any chemicals we might take in,” Green said. Her concern is pesticides. “There’s pollution everywhere, but this is something we can control,” she told me.

That there are synthetic chemical residues on conventional produce is not disputed. The question is whether or not the trace amounts of toxins are free of hazard.

“The dose makes the poison” is the dominant logic underpinning the science at the Environmental Protection Agency, the body charged with regulating pesticides. Testing used to establish safety levels for pesticides is based on checking for effects from higher-level doses, ones that would happen in, say, an accident during spraying crops. So far, researchers have paid scant attention to understanding the potential health risks from lower-level contact, such as ingesting the residues on conventional produce.

Consequently, the science investigating this question is only now emerging—and much has yet to be done. This dearth of data could be interpreted as an indication of safety. A high-profile 2012 Stanford meta-analysis comparing organic and conventional produce did just that. While the study confirmed that conventional food carried considerably more toxins than organic, it noted there was no health risk for consumers because the detected residues met EPA standards. Upon the study’s publication, its senior author, Dena Bravata, stated, “There isn’t much difference between organic and conventional foods if you’re an adult and making a decision based solely on your health.”

Nevertheless, ever more people like Green and O’Hagan are buying ever more organic food despite its price premium. The market hit almost $36 billion in 2014, up from just over $11 billion a decade earlier. Many consumers purchase organic for the same reason Green and O’Hagan do—because it’s produced without synthetic chemicals. According to the Organic Trade Association, which tracks consumer sentiment and behavior, half of all families that take home organic food do so because they believe it’s healthier. The top specific reason they give is that they’re “concerned about the effects of pesticides, hormones and antibiotics on children.”

If EPA standards don’t take into account dietary exposure, then what research exists and what can be gleaned about the effects? How big of a deal are these toxins? Are Green and O’Hagan and the millions of shoppers like them going overboard—and spending a lot more money—for no good reason?

Tracking Pesticides

In the early 2000s, while Cynthia Curl was earning her Ph.D. in environmental and occupational sciences at the University of Washington, in Seattle, she worked on an investigation that looked at children’s pesticide loads. The research focused on organophosphate insecticides, as has much science on the toxicity of pesticides, because these compounds are among the most commonly used in agriculture today. Adapted from nerve-gas agents employed in World War II, they’ve been sold under names such as chlorpyrifos, diazinon, and malathion. In larger doses, these chemicals work by disrupting certain nerve impulses that control the muscles and the lungs, causing paralysis and inducing suffocation and death—for bugs and humans alike.

But Curl and her colleagues wanted to understand the risks of lower-level exposure to organophosphates. Their study screened for the chemical in the children of workers who applied these pesticides as well as the offspring of farm laborers. The scientists then compared these two groups with youths in Seattle who had no obvious environmental contact with the chemicals—no pesticides were used in their homes or schools, for example.

(Photo: Getty Images)

To Curl and her colleagues’ surprise, the organophosphate metabolite levels in the Seattle cohort’s urine were much higher than the researchers had anticipated. (The standard method of determining exposure is by screening urine for the chemicals resulting from the body’s metabolism of the toxins.)

“Kids in Seattle were from wealthier families,” Curl told me. “I realized they were probably eating a lot more fruits and vegetables and I thought that might be the pathway.” So Curl decided to check out what role pesticide residues on produce played in the kids’ exposure. To that end, she screened 21 preschoolers who had eaten primarily conventional food for the previous three days and 18 kids who had consumed primarily organic food over those days. The tests she ran were for organophosphate metabolites. The 2003 study found that kids who ate conventional food had metabolite levels nine times higher than those who ate organic.

“Up until then people had thought there wasn’t really any difference between organic and conventional,” Curl told me. “This was the first study to show there was a measureable difference based on whether you had an organic or conventional diet.”

Five subsequent studies, one coauthored by Curl in 2015 that included almost 4,500 adults, have reached the same conclusion: Among people who don’t live in agricultural areas, conventional food appears to be the primary pathway for human exposure to organophosphate pesticides. These investigations also show that on an organic diet, organophosphate readings decline to almost non-detect levels. However, it’s important to note that the health effects of these chemicals are only beginning to be investigated. Researchers first needed to understand whether pesticide residues on produce were in fact making their way into people’s bodies.

Residuals

Every year, the Department of Agriculture’s Pesticide Data Program tests thousands of pieces of produce from across the country for chemicals. Its most recent report, using 2014 data, says almost 60 percent of the samples had pesticide residues. Some types of fruits and vegetables have a lot more than others—nearly all peaches, nectarines, cherries, and tomatoes tested positive for at least one pesticide. Some individual peaches, nectarines, cherries, and tomatoes carried traces of as many as 10 different pesticides.

These synthetic chemicals linger because that’s what they’re designed to do. They must persist on crops when it rains, when it’s hot, when the air cools at night. If pesticides were to readily break down or wash away, they couldn’t do their job.                                                                                               

Dana Boyd Barr, a research professor in environmental health at Emory University in Atlanta, laments the lack of science on the biological effects of dietary-level exposure. “We don’t know a lot of the things these pesticides can do to the human body,” she said. Boyd Barr has coauthored numerous studies monitoring the neurological development of children in agricultural communities and inner cities who were exposed in utero to organophosphate pesticides in the environment from bug spray used on crops and in urban buildings. (Until the last decade, organophosphates were commonly used in household insect sprays.)

Boyd Barr is critical of U.S. laws for allowing manufacturers to market chemicals with minimal, if any, safety testing. By contrast, the European Union system requires chemical makers to confirm a lack of human hazard before they’re able to sell their products. “I find it crazy that you can put something like organophosphate pesticides into the manufacturing process without establishing its safety for humans first,” she told me. “That puts the onus on people like me—academics coming at it from the outside—to determine if this manufacturer’s chemicals are harmful,” she said. “To me, that onus should be on the manufacturer.”

In the absence of such requirements, the science on the outcomes of low-level exposure is only slowly emerging. Two investigations point toward potential dangers.

In one, a 2012 experiment, cell biologists at the University of California, Irvine, exposed mice to triflumizole, a fungicide commonly used on produce, particularly leafy green vegetables. To check the effect of minor amounts, the researchers dosed pregnant mice at a level 400 times lower than the established “no observed adverse effect” level in rodents. They discovered that the pesticide appeared to induce certain fetal stem cells to develop into fat cells instead of bone cells, making the mice fatter. Based on what they observed, the study’s authors concluded that triflumizole could have the same effect in humans.

In another study, published in 2015, scientists at Harvard considered the impacts of eating conventional produce on human sperm production. The researchers observed 155 men who consumed produce that typically has higher levels of pesticide residues, such as berries, spinach, and apples. They compared these men’s sperm with that of men who ate a third as much of these fruits and vegetables daily. The men who ingested more had a 49 percent lower sperm count. They also had 32 percent fewer normally developed sperm.

More investigations are under way, among them a pilot study by Curl. Now an assistant professor in the Department of Community and Environmental Health at Boise State University, Ohio, she’s recruiting 20 pregnant women for the project. Half the expectant mothers will eat organic produce and half will eat conventional fruits and vegetables during their pregnancies. As with longitudinal studies conducted on farmworkers and their families that Boyd Barr has coauthored, Curl hopes to then follow the children as they reach school age, checking their neurological functions and other health outcomes. This study would begin to generate data within a few years but, until Curl establishes longer-term results, and until more researchers do similar studies, this science will hold little sway in how American regulators and the public understand the hazards of synthetic chemical pesticides.

In the meantime, the prevailing science says Americans needn’t worry. The USDA’s current pesticide residue report states that more than 99 percent of goods the agency sampled had residues the EPA considers safe.

Back at the Whole Foods, as Green and O’Hagan packed their groceries into tote bags, I asked if this was reassuring. “Why even take the chance of exposing ourselves to those chemicals?” O’Hagan said. “There are lots of chemicals we’ve been told were safe that we now know are really toxic. We used to put asbestos in everything. We thought it was perfectly OK but now we know how dangerous it is.”

Shouldering a tote bag and bundling Marlow into his coat, O’Hagan looked at me and said, “Besides, what’s eating organic going to hurt?”