Science, Tech & Environment

Your favorite produce probably comes with a side of pesticide

My wife constantly reminds me to wash our fruits and vegetables. My response is usually, “What the hell difference does it make?”

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It turns out, unfortunately, I am mostly right.

The Environmental Working Group is out with the latest version of its annual list of fruits and vegetables with the least and the most pesticide residues.

It tells a familiar story: many common fruits and vegetables that we enjoy eating contain pesticides that can’t be removed, even with washing.

Though organic food production is growing rapidly all around the world, pesticides are still widely used on America's farms. And as is often the case (see antibiotic resistance), as pests become resistant more pesticides are applied, which can mean more risky chemicals showing up in the foods we buy.

As in years past, apples top the list of the EWG’s “Dirty Dozen.” This year, researchers at EWG are particularly concerned about a chemical called diphenylamine, or DPA. Roughly 80 percent of American apples are sprayed with DPA after they’ve been picked to protect the skin of the fruit during shipping.

Sonya Lunder, a senior analyst with the EWG, says Europe put tight restrictions on the use of DPA in 2012, but the US has not followed suit.

Europe took action on DPA, Lunder says, because they “couldn’t guarantee consumers in Europe that this DPA treatment didn’t break down to form cancer causing impurities or breakdown products when the apples were stored.”

Number two on the dirty dozen list — strawberries.

“Strawberries grow on the ground,” Lunder says, “They’re very susceptible to pests and spoilage. They’re also a high value crop. So there’s a very aggressive regimen of treating strawberries, including fumigating the soil to kill all living creatures in the soil before they plant the little strawberry starts.”

Rounding out the top three produce items with the most pesticides: grapes.

Leafy greens aren’t off the hook though, Lunder says. Kale and collard greens are frequently contaminated with insecticides known to be toxic to the human nervous system. Also, in case you needed more bad news, potatoes have the most pesticides by weight.

Lunder says this doesn’t mean people should stop eating fruits and vegetables. Instead she advises us to choose organic when possible.

“If you have limited money to buy organic foods,” she says, “focus on those foods that are on the Dirty Dozen list, and when your organic dollars are tight, consider the Clean 15 as a group of foods that have very few pesticide residues on them.”

Some of the foods on the Clean 15 list include, avocados, which have the least pesticides of any food tested, sweet corn and pineapple. Researchers test the part of the produce people eat, and generally fruits and vegetables with a thick non-edible outer skin have fewer detectible residues.

Despite the guidance of groups like the EWG, shoppers are often left wondering about the safety of eating produce that has been treated with pesticides.

The science is not conclusive. In an NPR story from 2012, titled Why You Shouldn't Panic About Pesticide In Produce, Joseph Schwarcz, director of the Office for Science and Society at McGill University in Montreal, said it's a mistake to "equate the presence of a chemical with the presence of risk." 

"Where is the evidence that these trace residues are dangerous?" he asks. He claims there "just isn't much there."

Lunder says there’s no ethical way scientists can test humans to measure the safety of consuming pesticides. But, she says, several studies have examined the health outcomes of children who live in farming communities and were exposed to pesticides.

“These long term studies of American kids found that those with higher levels of exposure to pesticides had lower IQs and had signs that their brain and nervous system development had been altered or disrupted from the pesticides,” Lunder explains.

And in the IQ studies, Lunder points out, the researchers found a 6-point IQ drop, which is equivalent to lead poisoning.

Lunder says the children in the farm study were likely exposed to more pesticides than the residue in the food most of us eat. Young children and pregnant women are still most at-risk for problems associated with pesticides, however, so she advises people buying for those groups to be extra choosy in the produce department of the grocery store.

This story is based on an interview from PRI's environmental news magazine, Living on Earth.