An environmental organization has found that strawberries contain the largest amount of pesticide residue, with about a third of the fruit's samples having at least 10 pesticides.

A report released by the Environmental Working Group (EWG) has indicated that 70 percent of conventionally grown fruits and vegetables contain more than 230 pesticides.

Topping the group's 'Dirty Dozen' list of produce with the most pesticide residue was the strawberry, with spinach coming in at second place. Number three on the list are nectarines followed by apples, grapes, peaches, cherries, pears, tomatoes, celery, potatoes and sweet bell peppers.

The report, based on testing by the U.S. Department of Agriculture (USDA), noted that one sample of strawberry had 22 pesticide residues.

After the strawberry, the EWG found that the pesticide residue in spinach was nearly twice as high as other fruits or vegetables.

The report has been viewed with skepticism by some farming organizations like the Alliance for Food and Farming, which represents organic and non-organic growers.

According to USA Today, the group argued that the EWG's Dirty Dozen list is "unsupportable," and cited federal government data indicating that the residues were "well below safety levels" set by the Environmental Protection Agency (EPA).

Teresa Thorne, the executive director of the Alliance for Food and Farming, voiced her concern that the list could discourage low-income consumers from buying fruits and vegetables.

EWG also released its Clean Fifteen list which features fruits and vegetables that are "least likely to contain pesticide residues."

Avocados enjoy the top spot followed by sweet corn, with both having less than one percent of samples containing pesticides.

Third on the list are pineapples followed by cabbage, onions, frozen sweet peas, papayas, asparagus, mangoes, eggplants, honeydews, kiwis, cantaloupes, cauliflower and broccoli.

While pesticides have been regulated in the U.S. since the 1990s, some studies have indicated that there are still harmful chemicals being used.

The Daily Mail noted that some of these chemicals have been known to cause lasting health consequences including developmental problems in children.

Many pesticides have been banned since 1996 when legislation was passed to require the EPA to study and regulate pesticides. 

The EWG report noted that there is continued use of organophosphate insecticides, which is believed to be linked to ADHD in children.