Researchers looked at 48 popular produce items and reviewed 28,000 samples tested by the USDA and FDA to compile its list. According to the group, many pesticides pose health risks to people and have been linked to brain and nervous system toxicity, cancer, hormone disruption, and irritation of the skin, eyes and lungs. The EWG recommends people eat organic when possible.
Which conventionally-sold fruits and vegetables may you want to consider buying organic to reduce pesticide exposure? Keep clicking to see what the EWG found.
12. Hot peppersHot peppers kick off the EWG's "Dirty Dozen" list of 2013.
The group said its analysis of government tests found 67 percent of produce tested contained detectable pesticide residues -- even after they had been washed or peeled.
11. Cherry tomatoesNext on the "Dirty Dozen" are cherry tomatoes.
One single sample of cherry tomatoes tested positive for 13 different types of pesticides, the EWG's report found.
10. PotatoesPotatoes are among the most popular vegetables on American's plates.
The analysis showed the average potato had a much higher total weight of pesticides compared to any other food crop tested.
9. CucumbersUp next on the "Dirty Dozen" are cucumbers.
The EWG noted that it does not recommend skipping all the conventional fruits and vegetables featured on its list, pointing out the organization recommends these foods over less-healthy snacks or processed products. The group, however, recommends buying organic when possible.
8. Imported nectarinesEvery sample of imported nectarines in the EWG's analysis tested positive for pesticides.
7. Sweet bell peppersA single sample of sweet bell pepper contained 15 different pesticides, according to the Environmental Working Group.
6. SpinachSpinach was one of the most contaminated vegetables the Environmental Working Group's report found.
5. PeachesUp next on the "Dirty Dozen" are peaches.
"Pesticides are toxic by design and created expressly to kill living organisms -- insects, plants and fungi that are considered 'pests,'" the EWG emphasized in its report.
In October 2012, the American Academy of Pediatrics released a report saying parents who want to reduce their child's pesticide exposure may seek out organic fruits and vegetables, but added science hasn't proven that eating pesticide-free foods makes people any healthier.
"We just can't say for certain that organics is better without long-term controlled studies," the academy said.
4. CeleryLast year, celery ranked No. 2 on the EWG's "Dirty Dozen," after 96 percent of celery samples tested positive for one or more pesticides.
For the 2013 list, celery was the produce item that had the fourth-most contamination from pesticides, but was the most contaminated of the vegetables. One single sample of celery tested positive for 13 different types of pesticides.
3. GrapesGrapes had up to 15 pesticides detected on a single sample, the EWG found in the new report. As a category, grapes had more types of pesticides than any other produce, with 64 different chemicals.
Last year, grapes ranked seventh on the group's "Dirty Dozen" list.
2. StrawberriesStrawberries climbed from the fifth spot on the 2012 "Dirty Dozen" list to the second most-contaminated produce item in 2013.
1. ApplesSimilar to past years' lists, apples continue to be a major source of dietary pesticide exposure. The EWG found 99 percent of apples tested contained pesticides, and they contained the most residues overall.
Dr. Ken Spaeth, director of the Occupational and Environmental Medicine Center at North Shore-LIJ Health System in New York who was not involved in the rankings, pointed out to CBSNews.com that there's little evidence of health risks caused by long-term exposure to pesticide residue on produce. Most of the studies look at heavy exposure, like in farmers. However, if organic produce is available and within people's means (it is sometimes more expensive), it may be a reasonable choice for some, he said.
Spaeth also added that studies suggest the mere mechanical act of rinsing and rubbing while washing fruits and vegetables may reduce pesticide exposure.
Other offendersThe Environmental Working Group expanded it's "Dirty Dozen" list to highlight two crops that did not meet its traditional criteria for the "Dirty Dozen" rankings but still raised concerns. Leafy greens and summer squash raised the group's concerns because samples tested for organophosphate pesticides, which the EWG says have been linked to IQ deficits and problems with brain development in children, even at low doses. The EWG also found presence of organochlorine pesticides in some squash it tested, which has been linked to toxicity in wildlife.
Which fruits and vegetables had the least pesticides? The EWG also released a "Clean 15" list that found corn, onions and pineapples were the least-contaminated produce items.