The group, a nonprofit focused on public health, scoured nearly 100,000 produce pesticide reports from the U.S. Department of Agriculture and the U.S. Food and Drug Administration to determine what fruits and vegetables we eat have the highest, and lowest, amounts of chemical residue.

Most alarming are the fruits and vegetables dubbed the "Dirty Dozen," which contain 47 to 67 pesticides per serving. These foods are believed to be most susceptible because they have soft skin that tends to absorb more pesticides.

"It's critical people know what they are consuming," the Environmental Working Group's Amy Rosenthal said. "The list is based on pesticide tests conducted after the produce was washed with USDA high-power pressure water system. The numbers reflect the closest thing to what consumers are buying at the store."

Special report: Toxic America

The group suggests limiting consumption of pesticides by purchasing organic for the 12 fruits and vegetables.

"You can reduce your exposure to pesticides by up to 80 percent by buying the organic version of the Dirty Dozen," Rosenthal said.

The Dirty Dozen

Celery

Peaches

Strawberries

Apples

Domestic blueberries

Nectarines

Sweet bell peppers

Spinach, kale and collard greens

Cherries

Potatoes

Imported grapes

Lettuce

Not all non-organic fruits and vegetables have a high pesticide level. Some produce has a strong outer layer that provides a defense against pesticide contamination. The group found a number of non-organic fruits and vegetables dubbed the "Clean 15" that contained little to no pesticides.

The Clean 15

Onions

Avocados

Sweet corn

Pineapples

Mango

Sweet peas

Asparagus

Kiwi fruit

Cabbage

Eggplant

Cantaloupe

Watermelon

Grapefruit

Sweet potatoes

Sweet onions

What is a pesticide?

A pesticide is a mixture of chemical substances used on farms to destroy or prevent pests, diseases and weeds from affecting crops. According to the USDA, 45 percent of the world's crops are lost to damage or spoilage, so many farmers count on pesticides.

The Environmental Protection Agency, the FDA and the USDA work together to monitor and set limits as to how much pesticide can be used on farms and how much is safe to remain on the produce once it hits grocery store shelves.