(CNN) - Once again, strawberries top the list of the 12 "dirtiest" fruits and vegetables, according to the Environmental Working Group.
Every year since 2004, the group -- a nonprofit, nonpartisan environmental organization -- ranked pesticide contamination in 47 popular fruits and vegetables for its Shopper's Guide to Pesticides in Produce.
Pesticides include a wide array of chemicals that kill unwanted insects, plants, molds and rodents.
Spinach is the second dirtiest item on the "Dirty Dozen" list, followed by (in order of contamination) nectarines, apples, grapes, peaches, cherries, pears, tomatoes, celery, potatoes and sweet bell peppers. Each of these foods tested positive for pesticide residues and contained higher concentrations of pesticides than other produce.
In fact, nearly 70% of conventionally grown -- non-organic -- produce samples were contaminated, the tests indicated.
The 13th suspect
The shopper's guide is based on results of tests by the US Department of Agriculture and the Food and Drug Administration on more than 38,800 non-organic samples. The Environmental Working Group looks at six measures of contamination including the average number of pesticides found on samples and the average amount of pesticides found.
When testing samples, the USDA personnel wash or peel produce to mimic consumer practices.
A single sample of strawberries showed 20 pesticides, the report indicated. More than 98% of strawberries, spinach, peaches, nectarines, cherries and apples tested positive for at least one pesticide residue. And, on average, spinach samples had 1.8 times as much pesticide residue by weight than any other crop.
This year, the Dirty Dozen list is actually a "baker's dozen" and includes a 13th suspect: hot peppers. These were found to be contaminated with insecticides toxic to the human nervous system, according to the organization. Anyone who frequently eats hot peppers should buy organic, it says.
"If you cannot find or afford organic hot peppers, cook them, because pesticide levels typically diminish when food is cooked," the authors of the report noted.
'Chronic health implications'
Children are of special concern as younger bodies have greater susceptibility to pesticides than adult bodies, the report emphasizes.
Research "suggests that pesticides may induce chronic health complications in children, including neurodevelopmental or behavioral problems, birth defects, asthma, and cancer," noted the authors of a 2012 American Academy of Pediatricians report quoted by the Environmental Working Group.
Other studies indicate that a child's earliest exposure to pesticides -- through the mother during pregnancy -- may also be harmful.
Consumers who want to eat the dirty dozen fruits and veggies should buy organic, according to the organization.
Rinsing produce under tap water is an effective way to eliminate pesticide residues from produce, according to the Connecticut Agricultural Experiment Station, a government-run scientific group. Scientists there advocate rinsing all fresh produce under tap water for a minimum of 30 seconds before using.
Water is enough, the scientists say, as mild detergents or commercial vegetable washes do not increase the amount of pesticide residues you are able to wash away. However, a recent study from the University of Massachusetts, Amherst, suggests that soaking produce in a solution of baking soda and water is a more effective way to rid fruits and veggies of pesticides.
Tom Stenzel, president and CEO of the United Fresh Produce Association, says consumers should not rely on a shopping guide when deciding which fruits and vegetables to purchase. The industry group represents growers, shippers, fresh-cut processors, wholesalers, distributors and retailers.
"Consumers have more choices now than ever before when it comes to the fruits and vegetables they consume," Stenzel said.
"Food safety is a top priority for the industry, from field to fork," he said. "The fresh produce industry seeks to ensure a safe, efficient and timely supply chain, allowing consumers to experience fresh fruits and vegetables at the peak of their performance."
He encourages consumers to continue educating themselves about food safety and consult the Safe Fruits and Veggies website from the Alliance for Food and Farming, which represents both organic and conventional farmers.
"Empowering consumers with knowledge is key to helping them make healthy choices for their diets and that of their family," Stenzel said.
On a positive note, the Environmental Working Group also creates a lesser-known companion to the Dirty Dozen: the "Clean 15" guide to produce containing the least amount of pesticides.
Avocados lead 2018's clean fruits and veggies list, followed by sweet corn, pineapples, cabbage, onions, frozen sweet peas, papayas, asparagus, mangoes, eggplant, honeydew melon, kiwi, cantaloupe, cauliflower and broccoli.
Veggies placed in the top two spots -- avocados and sweet corn -- both showed pesticides on less than 1% of tested samples, the new report indicated. And more than 80% of pineapples, papayas, asparagus, onions and cabbages tested negative for pesticide residues.
The organization cautions that a small portion of sweet corn, papaya and summer squash sold in the US is produced from genetically modified seeds. It says anyone wanting to avoid genetically modified produce should buy organic varieties of these crops.
Through its healthy eating reminder, MyPlate, the USDA recommends that half your plate be filled with fruits and vegetables.
"Everything you eat and drink matters," the agency says. "The right mix can help you be healthier now and in the future."
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