What Heavy Metal Is in Kale? Understanding Your Superfood

November 28, 2025 •

4 min read

According to a 2024 study, certain leafy greens like kale have been observed to accumulate toxic heavy metals such as cadmium and lead from the soil. This raises the important question for many health-conscious consumers: exactly what heavy metal is in kale, and how much poses a risk?

Quick Summary

Kale and other leafy greens can absorb heavy metals like cadmium, lead, and thallium from their growing environment. Levels of contamination are influenced by soil quality and agricultural practices.

Key Points

Sources of Heavy Metals: Kale can absorb heavy metals like cadmium, lead, and thallium from contaminated soil, water, and agricultural products.
Bioaccumulation: Kale belongs to the Brassica family, which is known for its ability to bioaccumulate certain elements from the environment into its leaves.
Cadmium and Lead are Most Common: Cadmium and lead are the heavy metals most frequently associated with leafy green contamination, though often within international safety limits.
Thallium is a Concern in Processed Products: A 2025 case study demonstrated that processed kale chips can contain elevated levels of thallium due to the concentration process.
Mitigate Risk with a Varied Diet: To minimize exposure, rotate your leafy greens, consume kale in moderation, and choose products from reputable farms.
Nutritional Benefits vs. Risk: For the average person, the health benefits of kale generally outweigh the low risk of heavy metal exposure from moderate consumption.

Common Heavy Metals Found in Kale

While kale is a powerhouse of nutrients, it is also a brassica plant, a family known for its ability to absorb elements from the soil. Several heavy metals can be found in kale, with concentrations varying widely based on location and growing conditions. Understanding which metals are most common is the first step to assessing risk.

Cadmium (Cd)

Cadmium is one of the most frequently cited heavy metals found in kale and other leafy greens. Sources of cadmium contamination in agricultural soil include:

Certain phosphate fertilizers
Industrial pollution and emissions
Sewage sludge used as fertilizer

Research indicates that cadmium is particularly concerning because it accumulates in the kidneys and bones, potentially causing damage over long-term exposure. Some studies have found elevated levels of cadmium in kale compared to other vegetables.

Lead (Pb)

Lead is another heavy metal that kale can absorb from contaminated soil. Historically, lead contamination was linked to leaded gasoline and old paint, but modern agricultural sources include:

Some agrochemicals
Polluted irrigation water
Industrial fallout

Lead exposure can have severe health consequences, especially for children, affecting neurological development. However, many studies, including some cited in our research, have found lead levels in kales to be within acceptable international standards.

Thallium (Tl)

Thallium is a lesser-known but highly toxic heavy metal that kale can bioaccumulate. Interest in thallium in kale was amplified by a 2025 case study where a family's elevated thallium levels were traced back to contaminated kale chips.

Source: Thallium is naturally occurring but can be mobilized by mining, coal-burning plants, and other industrial processes.
Accumulation: Thallium concentration in foods can increase through manufacturing processes like dehydration, as seen with kale chips.
Health Risks: Even low-dose chronic exposure is a concern, with neurological and gastrointestinal symptoms noted in cases of high exposure.

Arsenic (As)

Arsenic is a toxic metalloid that can also be found in trace amounts in kale, absorbed from the soil. This is particularly relevant in areas with naturally high arsenic levels or industrial runoff.

How Heavy Metal Contamination Occurs

Heavy metal contamination in vegetables like kale is not intentional but a result of environmental factors. The primary pathway is absorption from the soil. The process is influenced by:

Soil Chemistry: The pH level of the soil can affect the bioavailability of heavy metals. For example, a lower pH often increases the uptake of certain metals.
Source Water: Using polluted water for irrigation, especially in developing countries, can be a major source of contamination.
Agricultural Inputs: Fertilizers derived from mining waste or industrial processes, as well as sewage sludge, can introduce heavy metals into the soil.
Industrial Proximity: Crops grown near industrial sites, incinerators, or high-traffic areas may have elevated heavy metal levels due to airborne particulates settling on the soil and leaves.

Risk Assessment and Regulatory Context

For the average consumer, the occasional consumption of kale from a reputable source is generally not a health risk. The concern arises from high-volume, long-term consumption or in cases where the produce is grown in heavily contaminated areas. Regulatory bodies, such as the FDA, have taken notice. For instance, the "Closer to Zero" plan aims to reduce exposure to heavy metals in food, particularly for infants and young children. International food standards from organizations like the WHO/FAO also set permissible limits for heavy metals in food crops.

Comparing Heavy Metals in Kale


Heavy Metal	Primary Contamination Source	Potential Health Risk (Chronic)	Example Context
Cadmium (Cd)	Phosphate fertilizers, industrial pollution	Kidney damage, bone issues	Elevated in some leafy greens
Lead (Pb)	Polluted water, old industrial sites, agrochemicals	Neurological damage (especially children)	Often within WHO limits but variable
Thallium (Tl)	Natural deposits, coal burning, dehydration process	Neuropathy, GI issues, hair loss	High levels noted in some kale chips
Arsenic (As)	Soil contamination, industrial waste	Increased risk of cancer, other illnesses	Present in trace amounts, varies by source
Nickel (Ni)	Sewage sludge, industrial sources	Allergic contact dermatitis, potential cancer risk	Can exceed limits depending on source

How to Reduce Heavy Metal Intake from Kale

While the presence of heavy metals in kale is a legitimate concern, several strategies can help minimize your risk:

Vary Your Diet: Don't rely on kale as your sole source of leafy greens. Incorporate a variety of vegetables into your diet to prevent the over-accumulation of any single contaminant.
Wash Thoroughly: While washing won't remove elements absorbed by the plant tissue, it will help remove any contaminants that may be on the surface of the leaves.
Choose Reputable Sources: Purchase kale from suppliers known for their quality control and sustainable farming practices. In some cases, knowing the soil quality of the farm can be beneficial.
Avoid Excessive Juicing: Juicing concentrates the compounds in kale, including potential heavy metals. Consuming huge quantities of juiced kale could significantly increase your intake over time.
Be Mindful of Processed Kale Products: As the thallium case highlighted, processing methods like dehydration can concentrate heavy metals further. Consider the source and processing methods of products like kale chips.

The Bottom Line

The presence of heavy metals in kale is a complex issue driven by environmental factors, not a reflection of the vegetable itself. For most people, the nutritional benefits of moderate kale consumption far outweigh the minimal risk of heavy metal exposure, especially when sourced from responsible growers. By adopting a balanced and varied diet, staying informed about food safety, and being mindful of processing, consumers can continue to enjoy this nutrient-dense superfood without unnecessary worry. For ongoing information on food contamination, you can consult sources like the National Institutes of Health (NIH).

Conclusion

In conclusion, kale can contain trace amounts of heavy metals like cadmium, lead, and thallium due to its growth environment, but the risk to the average consumer is low. Contamination levels are highly dependent on soil quality, industrial pollution, and agricultural practices. By diversifying your diet and choosing trusted sources, you can mitigate potential risks while still enjoying the significant health benefits of kale.

Frequently Asked Questions

While kale can absorb heavy metals from its environment, not all kale is contaminated. The concentration of heavy metals is highly dependent on factors like the soil's composition, water quality, and agricultural methods used where the kale was grown.

Organic certification primarily addresses pesticide use and does not guarantee freedom from naturally occurring heavy metals in the soil. Contamination risk is influenced more by soil quality than organic status.

Ingesting small, occasional amounts is unlikely to cause harm, but chronic, high-level exposure can be toxic. Effects vary by metal but can include neurological damage, kidney and bone issues, and gastrointestinal problems.

Washing kale can remove surface-level contaminants like dirt and some particulates. However, it cannot remove heavy metals that have been absorbed into the plant's tissue from the soil.

Processing kale, such as dehydrating it to make kale chips, can concentrate any heavy metals present in the plant. This was highlighted in a 2025 case study involving thallium exposure from contaminated kale chips.

Heavy metals can enter soil naturally or through human activities. Sources include industrial pollution, runoff from mining, wastewater used for irrigation, and agricultural products like certain fertilizers and sewage sludge.

No, you don't need to stop eating kale entirely. The key is moderation and sourcing from trusted growers. Balancing your diet with a variety of greens will help minimize your intake of any single compound or contaminant.

The FDA's 'Closer to Zero' plan is an action plan targeting toxic elements like lead, cadmium, and arsenic in baby food. Regulatory efforts for heavy metals in other food products are ongoing but still developing.