How Lead in the Soil Affects the Food We Eat, Including One of Our Favorite Snacks
By now, many have heard about the unhealthy levels of lead and cadmium in some dark chocolate. Dark chocolate is a favorite for many products used in cooking, baking, or just plain eating, known for its many health benefits. However, because lead can be found in the soil and air, dark chocolate is just one of the foods that can contain lead.
One might wonder: how does lead even get into chocolate? Lead is a toxic heavy metal that can be present in the soil that grows cocoa beans—which are the raw material for chocolate—as well as in the air and dust during their processing. The lead can also be absorbed by plants, such as cocoa trees, that are grown in contaminated soil. Therefore, when the cocoa beans are harvested, they may contain elevated levels of lead. The levels of lead in soil and cocoa beans can vary widely depending on the geographic location the beans are grown in and the sources of contamination. Beyond exposure through consuming foods containing lead, exposure to lead in soil directly can occur through inhalation of dust or through direct contact with skin, both of which can cause health problems.
Cocoa beans are typically grown in countries which often have less stringent regulations regarding the use of lead-containing pesticides and other sources of lead pollution. This can result in higher levels of lead in the soil, and in turn, in the cocoa beans. The level of lead that is considered safe in soil varies depending on the country, but generally ranges from 50–400 parts per million (ppm) or mg/kg. Soils with lead levels above this threshold may be considered contaminated and steps may be taken to remove or reduce the lead to safe levels. To minimize exposure to lead, it’s important to grow cocoa trees in soil that is free of lead and other toxic metals, as well as to properly store and handle cocoa beans during the post-harvest process. Additionally, best practices of using lead-free fertilizers, pesticides, and other chemicals, as well as proper waste management, should be applied.
“The industry should communicate to farmers the value of implementing Better Agricultural Practices related to reducing wet cocoa bean contact with soil during fermentation and drying,” wrote Timothy Ahn, co-author of the report who manages food safety at Lloyd’s Register. “Drying wet beans in direct contact with the ground, road surfaces, and concrete patios should be discontinued as a farmer controllable Pb (lead) reduction activity.”
Overall, it’s difficult to say how common the issue of lead contamination in cocoa beans is, as it depends on the region and source of the cocoa beans. Some efforts have been made to reduce the lead contamination in cocoa beans and chocolate, such as in the implementation of alternate agricultural practices and certifying the cocoa beans to meet certain standards. It’s also important to note that most of these studies are based on older data, and in many countries, regulations are now in place to limit the maximum acceptable lead levels in cocoa beans and chocolate.
The World Health Organization (WHO) has established a guideline value for lead of 0.1 micrograms per gram of chocolate. But again, it’s important to note that a lot of studies done on this topic were done on cocoa beans, not chocolate. This is because the end product is always different from the raw cocoa beans, i.e. chocolate is made FROM cocoa beans and other ingredients can be added during this process. Therefore, it’s hard to estimate the exact amount of lead in dark chocolate without knowing the origin of the cocoa beans and the manufacturing process.
The second toxic ingredient found in some chocolates is cadmium. It is also a toxic heavy metal that can be present in dark chocolate, among other foods. Similarly to lead, the amount of cadmium in chocolate depends on several factors, including the source of the cocoa beans and the growing conditions. In general, chocolate that is made from cocoa beans grown in areas with high levels of cadmium in the soil may contain higher levels of the metal. The World Health Organization (WHO) has established a guideline value for cadmium of 0.3 micrograms per gram of chocolate. Like the studies done on lead, a lot of studies done on this topic were done on levels of cadmium in cocoa beans, not chocolate. Therefore it is equally as difficult to estimate the exact amount of cadmium in dark chocolate without knowing the origin and the manufacturing process as well.
Consumer Reports, an independent, nonprofit organization that tests and rates consumer products, has conducted tests on a variety of chocolate products, including dark chocolate, to determine their lead content. These tests have demonstrated that some dark chocolate products have higher levels of lead than others. In some cases, the lead levels in individual dark chocolate bars have exceeded the recommended limit for lead in candy set by the Food and Drug Administration (FDA), at 0.1 parts per billion. However, again, many of the studies done on this topic were specific to cocoa beans, not chocolate. And even when the studies were done on chocolate, the testing methods and criteria likely differed among them.
In 2019, Consumer Reports found that 20% of chocolate bars exceeded the lead level limits set by California Prop 65, but were under the FDA limits. A follow-up report in 2021 found there was progress made in that none of the chocolate bars tested exceeded the higher California standards. Despite this progress, a further recommendation from Consumer Reports is that consumers should check the labels of their chocolate for any certifications, such as Rainforest Alliance or UTZ, which have strict standards for lead content in cocoa beans. You can learn more about lead content estimates for some of your favorite dark chocolate products here.
With all the conversation around dark chocolate, we ought to remember that because lead can be present in soil, it can be absorbed by anything planted in this contaminated soil. This contamination can come from various sources such as industrial activities, mining, and the use of lead-based products such as gasoline and paint. Some foods may be more likely to be contaminated by lead than others, including leafy greens and root vegetables, which tend to take up more lead from soil than other types of plants. Exposure to lead through contaminated food can occur through the consumption of food containing . This can be particularly concerning for vulnerable populations, such as pregnant women, young children, and aging adults, who may be more susceptible to the negative health effects of lead exposure. Lead can damage developing brains and nervous systems in children.
The US FDA has set limits for lead in certain foods, such as candy, juice, and canned foods, but there is no specific regulation for the maximum allowable level of lead in fruits, vegetables, and other products. To reduce exposure to lead in soil and food, it is important to choose fresh and organic produce, and to consider the source of the food and the growing conditions, when possible. Consuming a varied and balanced diet, as well as washing fruits and vegetables, can also be an effective way to minimize lead exposure from food.
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National Confectioners Association: https://candyusa.com/news/research-reveals-ways-lead-and-cadmium-in-chocolate-may-be-reduced/
California “Proposition 65” law: https://candyusa.com/news/court-establishes-guidelines-for-chocolate-sold-in-california/