What is the 'Dirty Dozen'?
The Environmental Working Group (EWG), a non-profit, non-partisan organization, has published its "Shopper's Guide to Pesticides in Produce" since 2004. This annual guide analyzes data from the U.S. Department of Agriculture (USDA) and the Food and Drug Administration (FDA) to identify fruits and vegetables with the highest and lowest pesticide concentrations. The list of the top 12 most contaminated produce is dubbed the "Dirty Dozen," while the list of the least contaminated is called the "Clean Fifteen". All produce is washed or peeled before testing, replicating how a consumer would prepare the food at home. The purpose of the guide is to give consumers a tool to make informed decisions about whether to prioritize buying organic produce, especially for items on the Dirty Dozen list.
How is the 'Dirty Dozen' determined?
The EWG's methodology has evolved over time. While originally based on the frequency and concentration of pesticide detections, the 2025 list incorporated a new metric that also considers the toxicity of the chemicals found. This approach provides a more comprehensive picture of the potential health risks associated with a particular item of produce. For example, some items like bell and hot peppers, though not always in the top rankings for residue concentration, have a higher toxicity score. The testing often reveals multiple pesticide residues on a single item, highlighting the complexity of agricultural chemical use.
Is conventional kale on the dirty list?
Yes, conventional kale has been a consistent presence on the EWG's "Dirty Dozen" list in recent years, including the 2025 report. Kale's inclusion came as a surprise to many in 2019, when it jumped to the third spot after being absent from the list for a decade. Subsequent testing has confirmed its status among the most pesticide-laden produce.
The reason for kale's high ranking is primarily due to the large number and variety of pesticide residues detected on conventionally grown samples. A 2019 report showed that over 92% of kale samples tested had two or more pesticide residues, with some individual samples containing as many as 18 different types. One of the most frequently found pesticides was Dacthal (DCPA), a potential carcinogen that has been banned in Europe since 2009. Its presence is particularly concerning because it is often applied to the soil, meaning it can be absorbed by the plant and not simply washed off the surface.
Why kale and other leafy greens?
The way leafy greens grow can contribute to higher pesticide exposure. Unlike fruits with thick peels that are discarded, such as bananas or avocados, the edible portion of kale is the leaf itself, which is directly exposed to pesticides sprayed to protect against insects and weeds. Furthermore, the crinkled, ruffled surface of kale leaves provides many places for residues to adhere, even after washing. This makes thorough cleaning more difficult compared to smoother-skinned produce.
Dirty Dozen vs. Clean Fifteen: A comparison
The EWG's two lists offer a way to prioritize your grocery spending, especially if buying 100% organic is not feasible for your budget. The Dirty Dozen highlights which items are most important to buy organic, while the Clean Fifteen lists produce where conventional options are likely safe.
| Feature | Dirty Dozen (e.g., Kale, Strawberries) | Clean Fifteen (e.g., Avocados, Onions) |
|---|---|---|
| Pesticide Residue Level | High concentration and variety of residues detected. | Low concentration; nearly 60% of samples in 2025 had no detectable pesticide residue. |
| Recommended Action | Prioritize buying organic to reduce exposure to pesticides. | Conventional options are generally low-risk and budget-friendly. |
| Examples of 2025 Items | Spinach, strawberries, kale, collard greens, grapes, peaches. | Pineapples, avocados, sweet corn, onions, cabbage, mangos. |
| Reason for ranking | Direct exposure of edible parts; multiple pesticide types found. | Protective skins or low pest pressure leading to less pesticide use. |
How to safely prepare kale and minimize pesticide exposure
Even with its place on the Dirty Dozen list, it's crucial to remember that eating kale and other vegetables is far better for your health than not eating them at all. The health benefits of a diet rich in fruits and vegetables outweigh the potential risks of low-level pesticide exposure. Here are several ways to minimize your exposure while still enjoying the nutritional powerhouse that is kale:
- Buy organic: This is the most effective way to avoid pesticide residues. Organic standards prohibit the use of most synthetic pesticides.
- Wash thoroughly: For conventional kale, washing is a must, though it won't remove everything. You can wash under running water while rubbing the leaves or try a vegetable soak.
- Soak in a solution: Some people opt for a simple soak using vinegar or baking soda. A mixture of 10% distilled white vinegar to 90% water is a common suggestion, though there is limited peer-reviewed research validating this method.
- Remove outer leaves: You can peel and discard the outer leaves of kale and other leafy greens, which may have higher concentrations of residues.
- Cook the kale: Cooking can help break down some pesticides, and it also reduces oxalates, which can be beneficial for some individuals.
- Support local, sustainable farms: Shopping at local farmers' markets can give you a better understanding of a farmer's growing practices. Some farms may use limited or no pesticides even if they are not officially certified organic.
The bottom line: Is conventional kale worth the risk?
For most people, the nutritional benefits of eating kale, whether conventional or organic, far outweigh the risks associated with residual pesticide exposure. Kale is packed with vitamins A, C, and K, as well as powerful antioxidants. Its high fiber content supports digestive health, and its potassium can help manage blood pressure. Concerns about pesticides are valid, and the EWG's lists provide a valuable framework for making smarter choices.
For individuals or families with health concerns, particularly children, who may be more susceptible to the effects of pesticide exposure, prioritizing organic kale is a wise decision. However, if your budget limits your ability to buy organic, simply eating conventional kale and other fruits and vegetables is the best choice. Combining these strategies can help you maximize the health benefits while minimizing any potential risks.
Conclusion
Yes, kale is currently on the Dirty Dozen list due to its high and frequent detection of pesticide residues in conventional farming. However, this information should not deter anyone from consuming this incredibly nutritious leafy green. Consumers can choose to buy organic kale, which has fewer pesticide residues, or, when buying conventional, they can take extra steps to wash and prepare the kale thoroughly. Ultimately, a diet rich in fruits and vegetables, regardless of how they are grown, is the most important factor for good health. Making informed, balanced choices based on your budget and health priorities is the key to a healthy lifestyle.
Sources for Further Reading:
- Environmental Working Group: Shopper's Guide to Pesticides in Produce: https://www.ewg.org/foodnews/
