Strawberries and spinach often contain pesticides even after washing, according to an annual report of toxic chemicals in produce

• The annual Dirty Dozen details which fruits and vegetables have been most contaminated by pesticides.
• Strawberries, spinach, and other greens had the most pesticides after washing.

Strawberries, spinach, and leafy greens once again topped a list of produce tainted by pesticides, according to an analysis from the Environmental Working Group.

The Dirty Dozen includes the 12 fruits and vegetables that retain the most pesticide contamination, even after they're washed and peeled as consumers would prepare them. It's updated annually as a part of EWG's Shopper's Guide, based on tests by the Department of Agriculture and the US Food and Drug Administration.

Nearly 70% of non-organic produce tested had detectable pesticide residue, usually at levels that fell within the legal limits in the US.

However, just because pesticides are legal does not mean that they are safe. More than a quarter of pesticide use in the US has been linked to chemicals that are illegal in Europe, according to a 2019 study; those chemicals have been banned due to probable or proven health risks.

Because the testers wash and prepare the produce samples before scanning for pesticides, these fruits and vegetables require more than an extra rinse to be rid of toxins.

Strawberries and greens topped the Dirty Dozen again

The USDA and FDA do not repeat tests of produce every year, so not much has changed since last year's Shopper's Guide was published.

For the seventh year in a row, strawberries were found to have the most pesticide contamination of any fruit or vegetable tested. Spinach came in second, followed by kale, collard greens, and mustard greens together in third.

The rest of the Dirty Dozen includes nectarines, apples, grapes, peppers (bell and hot), cherries, peaches, pears, celery, and tomatoes. Peppers moved up a couple spots on the list, but aside from that, the standings are the same as last year.

Whenever possible, the EWG recommends that people buy organic versions of Dirty Dozen produce, analyst Sydney Swanson said in a press release. Organic farming practices ban the use of most synthetic pesticides, so organic produce is less likely to be contaminated with known toxins.

However, not everyone can afford organic produce or have an environmentally-conscious market nearby. If you're unable to spring for cleaner versions of the Dirty Dozen, EWG experts recommend considering the Clean Fifteen.

Avocados, sweetcorn, and pineapple ruled the Clean Fifteen

The Clean Fifteen fruits and vegetables were found to have the lowest levels of pesticide residue out of the bunch, with nearly 70 percent of samples from the list found to be completely pesticide-free.

The list includes avocados, sweetcorn, and pineapple as the top three "cleanest" fruits and vegetables. Onions, papaya, and frozen sweet peas were next, followed by asparagus, honeydew melon, kiwi, and cabbage.

Mushrooms, cantaloupe, mangoes, watermelon, and sweet potatoes also made the list of the least pesticide-contaminated produce.

Since last year's list, the EWG removed broccoli, cauliflower, and eggplant from the Clean Fifteen — not because of new contaminants, but because they hadn't been tested in six or more years.

Industry experts are divided on whether ingesting pesticide residues may affect human health. EWG cited research from Harvard University that found people who ate pesticide-laden fruits and vegetables did not see a protective effect on health, even though the foods typically protect against cardiovascular disease and overall mortality, suggesting the pesticides cancel out the benefits.

However, other analyses have found no significant impact of pesticide residues on human health, according to the Alliance for Food and Farming. A representative of the group reached out to Insider with an analysis from the University of California's Personal Chemical Exposure Program, which found a child could eat hundreds to thousands of servings of a fruit or vegetable in a day and still not have any health effects from residues.