If kale, collard, or mustard greens are part of your weekly grocery list, you might want to take a closer look at what’s on those leaves. These nutrient-packed greens rank third on the Environmental Working Group’s 2025 Dirty Dozen list, which means they’re among the most pesticide-contaminated vegetables in the country.
Leafy greens are still among the healthiest foods you can eat. They’re packed with vitamins A and K, iron, and antioxidants that support heart health and immunity. But many conventionally grown greens carry chemical residues that could undermine their benefits. Let’s look at what scientists found on kale and its leafy cousins and how to reduce your exposure without giving up your favorite vegetables.
Kale, collard, and mustard greens: what’s really on them
The Environmental Working Group’s analysis of Department of Agriculture data found that nearly 60 percent of kale samples tested in the U.S. contained residues of DCPA, a pesticide the Environmental Protection Agency has classified as a “possible carcinogen” since 1995. In August 2024, the EPA suspended all uses of DCPA after new evidence showed it can interfere with thyroid hormone production.
But DCPA isn’t the only concern. The USDA found that kale, collard, and mustard greens were contaminated with traces of up to 21 different pesticides on a single sample. On average, each sample carried residues of more than five chemicals. About 86 percent of leafy greens tested had two or more pesticides detected. That’s higher than nearly any other produce category.
Other chemicals commonly found include bifenthrin and cypermethrin, two pyrethroid insecticides that studies have linked to potential effects on the developing nervous system. Imidacloprid—a neonicotinoid banned in Europe due to its toxicity to bees—also shows up frequently on these greens. Some studies have associated neonicotinoids with harm to the human nervous and reproductive systems.
The contamination isn’t just a surface issue. DCPA and other persistent chemicals can move through soil and water, traveling far beyond the fields where they’re sprayed. Tests in California and Washington have detected breakdown products of DCPA in groundwater, sometimes at levels above federal health advisory limits. Researchers have also found traces of the chemical in the air and dust of nearby homes.
Still, leafy greens remain one of the most nutrient-dense foods available. The goal isn’t to cut them out of your diet, but to handle and source them in smarter ways.
How to reduce pesticide exposure from leafy greens
If you eat kale, collards, or mustard greens regularly, a few simple steps can help you lower pesticide exposure.
- Choose organic when possible. Organic farming standards prohibit the use of synthetic pesticides like DCPA, bifenthrin, or imidacloprid.
- Wash thoroughly. Rinse greens under running water and use a clean brush for tougher leaves. Washing won’t remove all residues, but it can reduce surface contamination.
- Mix up your greens. Include vegetables from the Clean Fifteen—like cabbage, asparagus, or cauliflower—which tend to have much lower pesticide residues.
- Store smart. Keep greens dry and refrigerated in breathable containers. Moisture encourages decay, which can make pesticides more concentrated in spoiled areas.
Knowing where your food comes from and how it’s treated gives you control over what you’re really consuming. With a few mindful choices, you can keep enjoying your kale salads and collard wraps without as many unwanted chemical extras.