SEATTLE — Dark chocolate has a reputation as a relatively healthy treat, but research showing some popular bars might have potentially unsafe levels of heavy metals has many questioning how safe these treats are.

Consumer Reports tested 28 popular dark chocolate bars from Seattle’s own Theo Chocolate to Trader Joe’s, Hershey’s to Ghirardelli, and even smaller brands such as Alter Eco and Mast.

The study found cadmium and lead in every single bar.

With Valentine’s Day around the corner, Consumer Reports last month called on chocolate makers to commit by Feb. 14 to reducing levels of heavy metals in their bars. The letters were sent alongside a petition with nearly 55,000 signatures.

With no federal limit set on heavy metals in foods, researchers used California’s limitations on lead and cadmium, the most protective in the country, to determine which chocolates posed the most risk.

California’s daily maximum allowable dose levels (MADL), set by Proposition 65, require businesses to provide warnings to Californians if a product leads to toxic chemical exposures that can cause cancer, birth defects, or other reproductive harm. The limits were set for lead starting in 1988 and cadmium in 1997.


For 23 of the chocolate bars Consumer Reports tested, eating just 1 ounce exceeded California’s limits of 0.5 micrograms per day for lead – or about 1% of the weight of the average grain of sand – and 4.1 micrograms per day for cadmium.

One ounce of Theo’s Organic Extra Dark Pure Dark Chocolate 85% Cocoa chocolate bar, which is roughly one serving size, contained 140% of California’s maximum daily allowable dose of lead and 189% of the dose of cadmium, Consumer Reports found.

Consumer Reports also listed Theo’s Organic Pure Dark 70% Cocoa as having high levels of both.

Although Consumer Reports cites MADL guidelines, official food safety standards are based on different limits. Many of the brands producing the chocolate bars tested in the study, including Theo Chocolate, follow thresholds set by a 2018 California consent judgment. The judgment established concentration limits for lead and cadmium that the chocolate industry follows.

Under California law, the concentration levels set in the judgment supersede the standards cited in the study; bars that contain levels above those set in the judgment require warning labels when sold in California.

“At Theo, the safety and quality of our products is our top priority, and we are confident that our products meet the standards outlined in our industry and are safe to be consumed,” said a Theo Chocolate spokesperson in an emailed statement.


“All products in the study – including Theo – are well under these limits,” the spokesperson said, referring to the 2018 standards.

Both the 70% and 85% Theo chocolate bars fall below the judgment’s threshold for lead and cadmium in chocolate bars with 65% to 95% cacao content.

Consistent, long-term exposure to even small amounts of heavy metals like lead and cadmium can cause a variety of health problems, particularly in children and pregnant people.

Lead exposure can slow the growth and development of children, particularly “their brain development, behavioral development and can even cause aggressive behaviors,” said Dr. Holly Davies, a toxicologist at the Washington State Department of Health.

Cadmium exposure can cause damage to the kidneys, lungs, and bones, she said.

Lead exposure becomes more dangerous as it accumulates in the body, and it can also cause hypertension and neurological effects, Davies said.


Five of the 28 bars Consumer Reports tested had levels of lead and cadmium below California’s MADL limits. Those safer bars were Ghirardelli Intense Dark (both 72% and 86% cacao), Taza Chocolate Deliciously Dark (70%), Mast Dark Chocolate (80%), and Valrhona Abinao (85%).

In response to the 2018 consent judgment, the National Confectioners Association and nonprofit advocacy group As You Sow – with contributions from more than 30 chocolate companies (including Theo) – released a three-year expert research study. The study concluded in August 2022.

The expert committee unanimously agreed it is feasible for the chocolate industry to manufacture chocolate products with lower levels of lead than the thresholds outlined in the judgment, although they did not agree on what those levels are.

The experts did not reach an agreement on whether the chocolate industry can produce products with lower levels of cadmium than those in the judgment.

Within their recommendations, only one member, toxicologist Michael DiBartolomeis, provided recommendations for maximum thresholds of both lead and cadmium. DiBartolomeis’ recommendations are lower than the judgment and MADL thresholds.

Both Theo chocolate bars included in the Consumer Reports study had lead and cadmium levels above DiBartolomeis’ recommended limits for chocolate bars with 65% to 95% cacao content.


The expert committee also found cadmium exposure in cacao occurs naturally before harvest, while lead levels are influenced by where and how the cocoa beans are handled by humans after harvest.

The committee recommended changes to harvesting and manufacturing processes such as decreasing soil contact or even changing the pH of soils to reduce exposure to lead and cadmium.

The Consumer Reports letters calling for several chocolate makers to take action by Feb. 14 come after more than a dozen lawsuits against leading manufacturers since the release of the December study.

Consumers have sued Trader Joe’s at least nine times over its dark chocolate products, most recently with a pair of class-action lawsuits out of New York.

Hershey’s, which makes another one of the chocolate bars tested in the Consumer Reports study, is facing its class-action lawsuit filed in the same court as one of the suits against Trader Joe’s.

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