Why you shouldn't freak out about pesticides, according to a toxicologist

To buy organic, or not to buy organic?

That question has probably pained every grocery shopper with a budget large enough to consider it.

Every year, an organization called the Environmental Working Group (EWG) tries to help answer this question by highlighting which foods have the most and least "pesticide loads" - the chemicals organic produce is supposed to be grown without. EWG's "Dirty Dozen" list ranks the 12 fruits and vegetables with the highest levels - it includes strawberries, peaches, spinach, and tomatoes.

There's a small problem with the ranking, however, according to Dr. Carl Winter, a professor of toxicology at the University of California, Davis.

The list doesn't use a standard test designed to tell whether something is dangerous for human health. EWG measures the amount of pesticide residues on each piece of produce, but doesn't take into account the tenet that the dose makes the poison.

In other words, the amounts of pesticides found on the Dirty Dozen list are too small to merit concern in the first place.

"Typical US consumer exposure to the most common pesticides found on the [list] is at a tiny fraction of what would be of health concern," Winter told Business Insider.

To decide whether a food or other substance is safe to eat or use, toxicologists like Winter - who specialize in studying the effects of chemicals on the body - focus on three main things.

1. Toxicity of the thing being studied (in this case, pesticides)
2. The amount of consumption of the food with said pesticides in it
3. The residue levels of pesticides found on the food

The "Dirty Dozen" doesn't look at any of the three, Winter says.

Winter recently peeled apart the components of the "Dirty Dozen" ranking in a study he co-authored, which was published in the Journal of Toxicology. In the paper, he finds the following issues with the system used to classify produce as "dirty":

1. Of the most commonly detected pesticides found on the 12 pieces of produce that the EWG listed as "dirty," Winter found the amounts were so low that they "pose negligible risks to consumers"
2. Eating organic forms of those 12 fruits and veggies instead doesn't significantly reduce any of those negligible risks
3. The methodology used by the EWG "lacks scientific credibility."

So why does the EWG continue to come out with its "Dirty Dozen" list every year, even though it doesn't really tell you how dangerous specific foods are?

According to Monica Amarelo, EWG's director of communications, "the Shopper's Guide is not and has never claimed to be a risk assessment. It's a straightforward ranking of which fruits and vegetables tested by the USDA had the most pesticides."

And some researchers say this has some value, at least for people with young children or toddlers. Indeed, some evidence - such as a 2012 study published in the journal Pediatrics - suggests pesticide exposure may affect little ones more acutely than it does adults.

"Even low levels of pesticide exposure can be harmful to infants, babies and young children, so when possible, parents and caregivers should take steps to lower children's exposures to pesticides while still feeding them diets rich in healthy fruits and vegetables," Dr. Philip Landrigan, a pediatrician at the Mt. Sinai School of Medicine in New York, tells USA Today.

Winter disagrees.

"This latest iteration of the 'Dirty Dozen' follows the same flawed methodology as all of its predecessors and therefore is of dubious value to consumers," Winter says. "My biggest concern is that attention given to the 'Dirty Dozen' will discourage consumers from eating enough fruits and vegetables (either conventional or organic) which will do them much more harm than good."

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