Almost six out of 10 kale samples tainted by pesticide banned in Europe 15 years ago
By Alexis Temkin, PhD, Senior Toxicologist
Nearly 60 percent of kale samples sold in the U.S. were contaminated with residues of a pesticide that the Environmental Protection Agency considers a possible human carcinogen, according to EWG's analysis of 2017 Department of Agriculture test data. (2017 is the most recent year that the USDA tested kale as part of its Pesticide Data Program.)
The pesticide is DCPA, often marketed as Dacthal, which the EPA classified as a “possible carcinogen” in 1995. In 2005, under market pressure, Dacthal’s major manufacturer terminated its registration for use on several U.S. crops, including artichokes, beans and cucumbers, after studies found that its breakdown products were highly persistent in the environment and could contaminate drinking water sources.
For these reasons, in 2009 the European Union prohibited all uses of DCPA. In 2023, the EPA released a draft risk assessment that stated DPCA shows “significant risks to human health,” especially for pregnant people. Although the use of DCPA is under review by the EPA, it is still used in the U.S. on crops such as kale, broccoli, sweet potatoes, eggplant and turnips.
Other leafy greens are also widely contaminated with DCPA. More than 35 percent of collard and mustard green samples analyzed by the USDA in 2019 were tainted with detectable levels of DCPA.
Kale, other leafy greens contaminated with numerous pesticides
Leafy greens' popularity as health foods rich in vitamins and antioxidants has soared in recent years. Dacthal is far from the only pesticide used on kale and other leafy greens.
In fact, of all the produce the USDA tested, the agency found the most pesticides on kale, collard and mustard greens, with 103 different chemicals found across the category.
On average, leafy green samples, such as kale, collards and mustard greens, had detectable levels of more than 5 different pesticides, with up to 21 different pesticides on a single sample.
And 86 percent of samples had detectable levels of two or more pesticide residues.
That’s why kale, collard and mustard greens are third on the 2024 Dirty Dozen™.
Dacthal linked to cancer, other health harms
According to U.S. Geological Survey data from 2016, about 500,000 pounds of DCPA were sprayed in the U.S., mostly in California and Washington state. In California, the only state where all pesticide use must be reported, nearly 200,000 pounds were sprayed in 2016.
EWG-commissioned tests of kale purchased from grocery stores in 2018 found that on two of eight samples, DCPA residues were comparable to the average level reported by the USDA.
The EPA’s 1995 classification of DCPA as a possible carcinogen noted increases in liver and thyroid tumors. DCPA can also cause harm to the lungs, liver, kidney and thyroid.
In California and Washington, concerns have grown about the capacity of the pesticide’s breakdown products to contaminate surface and groundwater. Not only can DCPA contaminate areas near its use but studies show it can also travel long distances in the atmosphere.
In California, DCPA’s breakdown products were detected in groundwater wells above the EPA health advisory level for these contaminants, triggering potential action to restrict the use of DCPA under state law. But Amvac, a California-based DCPA manufacturer, argued that such uses were not a concern for human health. Siding with the manufacturer, the California Office of Environmental Health Hazard disregarded the human health risks of this pesticide.
A report by the Washington Department of Agriculture recommended a complete phaseout of DCPA in the state beginning in 2015. The latest groundwater tests from 2019 and 2020 found DCPA breakdown products at concerning concentrations in parts of the state, and the agency is still assessing water contamination.
Source: EWG, from California Department of Pesticide Regulation and the U.S. Geological Survey's Pesticide National Synthesis Project.
DCPA can also drift into the air and homes around farms where it is sprayed. A 2019 study led by scientists at the University of California at Berkeley School of Public Health found that more than 50 percent of adolescent girls from farm communities in the Salinas Valley were exposed to DCPA. This is especially concerning given that the pesticide is also a suspected endocrine disruptor – a chemical that can affect hormones – and may be particularly harmful to thyroid function.
In 2014, the EPA reviewed DCPA as part of the Endocrine Disruptor Screening Program, concluding that it may interact with thyroid signaling, and requested more data from the manufacturer, Amvac, on thyroid toxicity for sensitive populations like children and the developing fetus. Nearly a decade later, Amvac finally submitted the requested study to the EPA, which concluded that the chemical could pose serious risks to pregnant people and their offspring. The agency is still determining if DCPA can safely be used, or to terminate all uses.
Other concerning pesticides on leafy greens
One of every four leafy green samples contained bifenthrin and cypermethrin, two types of pyrethroid insecticides. Recent epidemiological data finds that metabolites of these pesticides detected in the urine of children are associated with adverse neurological outcomes, such as attention deficit/hyperactivity disorder.
Previous USDA kale tests showed 30 percent of kale samples also had detectable levels of imidacloprid, a potentially neurotoxic neonicotinoid insecticide banned in the EU because of harm to bees. But the USDA's 2017 testing did not analyze kale for imidacloprid, even though it is still likely used on the crop. In an email to EWG, the USDA explained the omission was because imidacloprid was inadvertently left off the list of compounds to be tested by its lab.
Imidacloprid was detected on 30 percent of collard greens and 27 percent of mustard greens in 2019 USDA samples. (That’s the most recent year during which these produce items were tested)
EWG’s recommendations for leafy greens
As with all produce, EWG recommends choosing kale, collard and mustard greens that are organically grown.
Kale and other leafy greens are extremely nutritious vegetables, high in vitamins A and K and iron, and consumption of leafy greens is associated with reduced risk for cardiovascular disease.
We also recommend using greens in recipes with ingredients like lemon juice, red peppers or tomatoes, which are rich in vitamin C, since that helps the body absorb their plentiful nutrients.
This article was adapted and updated from the 2021 Shopper's Guide to Pesticides in Produce™.
About EWG’s Shopper’s Guide to Pesticides in Produce
EWG's Shopper’s Guide to Pesticides in Produce is a suite of materials investigating the presence of pesticides in foods and the ways they could harm people, especially children – and to help consumers make the best, most informed choices for their families.
We’ve published the guide nearly every year since 2004.
EWG's Shopper’s Guide is designed to support people who would like to minimize their exposure to pesticides. It includes two well-known lists: the Dirty Dozen, or the 12 fresh non-organic, or conventional, fruits and vegetables with the highest pesticide residues, as well as the Clean Fifteen, the conventionally grown fruits and vegetables with very low or no traces of pesticides.
Some pesticides have more data linking them to health concerns than others. These pesticides are particularly concerning for children, who are especially susceptible to many of the health harms associated with pesticide exposure.
The presence of so many different pesticides in foods is also problematic. There’s little data available about how multiple pesticides interact with each other in the body or how such mixtures could compound each chemical’s individual potential health harms. But the data we do have suggests that when chemicals are present in a mixture, they may be toxic to humans at lower levels than when alone.
When regulating pesticides, government bodies also consider them only one at a time. They don’t look at the potential total body burden for consumers.
