Many shoppers don’t realize that pesticide residues are common on conventionally grown produce – even after it is carefully washed or peeled. EWG’s analysis of tests by the U.S. Department of Agriculture found that nearly 70 percent of samples of conventionally grown produce were contaminated with pesticide residues.

The USDA tests found a total of 230 different pesticides and pesticide breakdown products on the thousands of produce samples analyzed. EWG’s analysis of the tests shows that there are stark differences among various types of produce. The EWG’s “Shopper’s Guide to Pesticides in Produce” lists the trademarked “Dirty Dozen” list of fruits and vegetables with the most pesticide residues, and the trademarked “Clean Fifteen” for which few, if any, residues were detected.

Twenty-five years after the National Academy of Sciences issued a landmark report raising concerns about children’s exposure to toxic pesticides through their diets, Americans still consume a mixture of pesticides every day. While vegetables and fruits are essential components of a healthy diet, research suggests that pesticides in produce may pose subtle health risks.

A recent study in JAMA Internal Medicine, a journal of the American Medical Association, found a surprising association between consuming high-pesticide-residue foods and fertility problems among participants in the Harvard University EARTH study.

Women who reported eating two or more servings per day of produce with higher pesticide residues were 26 percent less likely to have a successful pregnancy during the study than participants who ate fewer servings of these foods. A previous study of male participants found similar associations between consumption of high-residue produce and reproductive health. Both studies drew from couples seeking treatment at a fertility clinic, and found that the frequency of eating fruits and vegetables with fewer pesticide residues was not associated with fertility outcomes.

The findings from the EARTH studies raise important questions about the safety of pesticide mixtures found on produce, and suggest that people should focus on eating the fruits and vegetables with the fewest pesticide residues. importantly, the studies’ definition of higher and lower pesticide foods mirrors EWG’s Dirty Dozen and Clean Fifteen lists. So, when buying organic produce is not an option, use the Shopper’s Guide to choose conventional foods lower in pesticide residues. With the Guide, you can have the health benefits of a diet rich in fruits and vegetables while limiting your exposure to pesticides.

For the 2018 Dirty Dozen list, EWG singled out produce with the highest loads of pesticide residues. This year the list includes, in descending order, strawberries, spinach, nectarines, apples, grapes, peaches, cherries, pears, tomatoes, celery, potatoes and sweet bell peppers.

Each of these foods tested positive for a number of different pesticide residues and contained higher concentrations of pesticides than other produce.

Key findings:

More than 98 percent of samples of strawberries, spinach, peaches, nectarines, cherries and apples tested positive for residue of at least one pesticide.

A single sample of strawberries showed 20 different pesticides.

Spinach samples had, on average, 1.8 times as much pesticide residue by weight than any other crop.

Again this year, EWG has expanded the Dirty Dozen list to highlight hot peppers, which do not meet our traditional ranking criteria but were found to be contaminated with insecticides toxic to the human nervous system.

The USDA tests of 739 samples of hot peppers in 2010 and 2011 found residues of three highly toxic insecticides – acephate, chlorpyrifos and oxamyl – on a portion of sampled peppers at concentrations high enough to cause concern. These insecticides are banned on some crops but still allowed on hot peppers. In 2015, California regulators tested 72 unwashed hot peppers and found that residues of these three pesticides are still occasionally detected on the crop.4

EWG recommends that people who frequently eat hot peppers buy organic. If you cannot find or afford organic hot peppers, cook them, because pesticide levels typically diminish when food is cooked.

EWG’s Clean Fifteen list of produce least likely to contain pesticide residues includes avocados, sweet corn, pineapples, cabbages, onions, frozen sweet peas, papayas, asparagus, mangoes, eggplants, honeydews, kiwis, cantaloupes, cauliflower and broccoli. Relatively few pesticides were detected on these foods, and tests found low total concentrations of pesticide residues.

Key findings:

Avocados and sweet corn were the cleanest. Less than 1 percent of samples showed any detectable pesticides.

More than 80 percent of pineapples, papayas, asparagus, onions and cabbages had no pesticide residues.

No single fruit sample from the Clean Fifteen tested positive for more than four pesticides.

Multiple pesticide residues are extremely rare on Clean Fifteen vegetables. only 5 percent of Clean Fifteen vegetable samples had two or more pesticides.

The Shopper’s Guide ranks pesticide contamination on 47 popular fruits and vegetables based on an analysis of more than 38,800 samples taken by the USDA and the Food and Drug Administration. The USDA doesn’t test every food every year, so EWG generally uses data from the most recent one- or two-year sampling period for each food. The USDA doesn’t test two fruits, honeydew melons and kiwis, so EWG uses data from the Food and Drug Administration’s pesticide monitoring for these crops. Additional details from the Environmental Working Group on its website.