It’s a widely accepted fact that a diet rich in fruits and vegetables is vital for maintaining good health and can help prevent serious illnesses, including cancer. However, a new study has uncovered some unsettling truths about certain produce items that may harbor harmful chemicals.

In their latest report, the Environmental Working Group (EWG), a respected consumer advocacy organization, has scrutinized nearly 50 types of fruits, vegetables, and legumes. The focus of their investigation was to determine the levels of pesticide residues present in these foods, revealing a concerning picture.

Pesticides, which are commonly used in agriculture to protect crops, have long been associated with various health risks. Scientific research has linked these chemicals to damage at the cellular level, hormonal imbalances, and inflammation, all of which can increase the likelihood of developing cancerous tumors.

From their analysis, the EWG has compiled a list known as the ‘dirty dozen’ for 2025, highlighting the produce items most contaminated with pesticide residues by weight.

Topping this list is spinach, earning the unfortunate title of the ‘dirtiest’ among the examined produce. An alarming three-quarters of non-organic spinach samples were found to contain the insecticide permethrin. This chemical is prohibited for use on food crops in Europe due to its potential health risks. While deemed safe in small doses, excessive exposure to permethrin has been linked to nervous system damage, muscle weakness, tremors, and seizures.

Spinach was the ‘dirtiest’ item on the list, with three-quarters of non-organic samples containing the insecticide permethrin, which is banned from use on food crops in Europe. While considered safe in low amounts, excessive exposure has been shown to damage the nervous system and lead to muscle weakness, tremors and seizures.

About 40 percent of spinach samples also contained dichlorodiphenyltrichloroethane (DDT), which was banned by the Environmental Protection Agency (EPA) in 1972 over concerns about widespread environmental damage.

Strawberries, leafy greens such as kale, grapes and peaches rounded out the top five dirtiest foods, with people consuming them reporting significantly higher pesticide levels in their urine compared to those who ate lower-residue produce.

Researchers at the Environmental Working Group (EWG) have compiled their list of the ‘dirtiest’ fruits, vegetables and legumes (stock image)

Dr Alexis Temkin, lead study author and vice president for science at EWG, said: ‘The findings reinforce that what we eat directly affects the level of pesticides in our bodies.

‘Eating produce is essential to a healthy diet, but it can also increase exposure to pesticides.’

In the new analysis, EWG researchers gathered data from the US Department of Agriculture (USDA) on pesticide residue in non-organic produce collected nationwide between 2013 and 2018.

These findings were combined with dietary survey responses and urine biomonitoring data from 1,837 Americans in the CDC’s National Health and Nutrition Examination Survey (NHANES) from 2015 to 2016, the most recent figures available.

Scientists took this information and developed a ‘dietary pesticide exposure score’ that estimates a person’s exposure based on consumed fruits and vegetables and the residue on them. 

The team then compared exposure scores with 15 pesticide biomarkers in each participants’ urine. 

The 12 dirtiest fruits and vegetables are: spinach; strawberries; kale, collard and mustard greens; grapes, peaches, cherries, nectarines, pears, apples, blackberries, blueberries and potatoes. 

Spinach was considered the dirtiest food. The researchers found that according to the USDA’s most recent tests, which were conducted in 2016, there was a sharp increase in pesticide residue on non-organic spinach since the crop was previously tested in 2008 and 2009. 

There was an average of seven pesticides on non-organic spinach samples, with up to 19 different ones on a single sample. 

About 76 percent of samples contained residue of permethrin, which has been banned on food crops in Europe since 2000. It is restricted in the US due to extreme toxicity to fish and is meant to be limited in crops. 

In 2016, 16 of 707 spinach samples had concentrations that violated the EPA’s maximum pesticide residue limits for permethrin. 

The USDA also found 83 spinach samples with residue of other pesticides that are prohibited for use on spinach but legal on other food crops. 

Strawberries were the second dirtiest food on the list. Though Americans consume about eight pounds of fresh strawberries per year, 99 percent of samples had detectable residue of at least one pesticide, and about 30 percent had 10 or more pesticides.

Among the most dangerous detected pesticides was carbendazim, a hormone-disrupting fungicide that studies suggest may damage the male reproductive system. It was detected on 16 percent of samples. 

Spinach was considered the ‘dirtiest’ food due to high amounts of potentially cancer-causing pesticides (stock images)

Pineapples were the ‘cleanest’ food due to the protective skin reducing pesticide residue (stock image)

Kale, collard and mustard greens ended up as third dirtiest on the list due to nearly 60 percent of samples sold in the US containing residue from pesticides considered possible human carcinogens. 

Additionally, 35 percent of collard and mustard green samples in 2019 had detectable levels of the pesticide Dimethyl tetrachloroterephthalate (DCPA), also known as Dacthal. In August 2024, the EPA issued an emergency suspension of DCPA due to thyroid toxicity and health consequences to fetuses.

Grapes landed at number four while peaches were in fifth for the worst foods. In some recent studies, grapes have been found to contain as many as 26 different pesticides, while as many as 59 different pesticides have been found on peaches.

The 12th and final item on the Dirty Dozen list was potatoes, the most consumed vegetable in the US. This was the first year the vegetable had made the list. 

The EWG team said this was due to high concentrations of chlorpropham, a plant growth regulator banned in the European Union due to health concerns such as thyroid disruptions. 

The researchers also revealed the ‘Clean 15’ list. A the top was pineapples, which the EWG said are low in pesticides due to the fruit’s thick, inedible skin protecting it. 

Sweet corn, avocados, papayas and onions all rounded out the top five cleanest foods. 

The full list of the ‘cleanest foods is: pineapples; sweet corn; avocados; papayas; onions; frozen sweet peas; asparagus; cabbages; watermelon; cauliflower; bananas; mangoes; carrots; mushrooms; and kiwi. 

‘This study builds on previous work showing that certain fruits and vegetables are a major route of pesticide exposure for millions of Americans,’ Temkin said. ‘Young children and pregnant people are particularly susceptible to the harms from exposure.’