Frequent exposure to even small amounts of lead, arsenic, cadmium, and other heavy metals is dangerous, in part because it’s difficult for the human body to break them down or excrete them. And over time, exposure to those heavy metals can harm health. In children, it can affect brain development, increasing the risk for behavioral problems and lower IQ. In adults, it can contribute to central nervous system problems, reproductive problems, and hypertension, and can damage kidney and immune function.

“Since the risks are serious,” Rogers says, “it pays to limit your intake of heavy metals as much as possible.”

Heavy metals can show up in food if the water or soil where food is grown contains them naturally or is contaminated because of pesticides or industrial uses, says Tunde Akinleye, a CR chemist who oversaw the testing. Heavy metals may also get into food, including herbs and spices, during manufacturing—from processing equipment or packaging, for example.

Laura Shumow, executive director of the American Spice Trade Association, says it’s almost impossible to rid herbs and spices of all heavy metals because of “the unavoidable presence in the environments where they are grown.” She also says the amount of heavy metals absorbed from the soil, and the part of the plant where they can end up, differs from plant to plant. The trade group offers companies guidance on how to limit contaminants that they can implement with their suppliers.

Shumow says that according to a recent risk analysis by the ASTA, spices make up less than 0.1 percent of dietary lead exposure in children ages 1 to 6. And even for adults, she says, the ASTA believes the risk is low “in large part because spices are a very small component of the diet.”

But CR’s data underscore a broader problem. “People reach for the herbs and spices in their kitchens multiple times a day,” Akinleye says. And for certain spices, just one serving—¾ teaspoon or more—per day leaves little room for heavy metal exposure from other sources. For example, CR’s previous testing found that some brands of fruit juice, baby food, and rice contain troubling amounts of heavy metals.

And smaller amounts of certain products could be a concern if they are combined with others in a recipe. For example, a dish that has just ¼ teaspoon each of Great Value (Walmart) Chili Powder, Trader Joe’s Organic Cumin, and La Flor Oregano per serving would contain enough arsenic, cadmium, and lead to pose a concern.

Other research also suggests that herbs and spices can contribute to heavy metal exposure. For instance, a 2018 study in Morbidity and Mortality Weekly Report found high lead levels in 22 percent of food samples—mostly spices and herbal remedies—taken from homes of children with lead poisoning in North Carolina.

And a 2010 study linked a case of lead poisoning in a 12-month-old Massachusetts boy in part to turmeric used by the family. Five similar cases were later discovered in Arizona, California, Colorado, Connecticut, and New York. And more than a dozen turmeric products have been recalled since 2011.

CR’s tests, however, demonstrate that it is possible for herb and spice companies to limit heavy metals in their products. “About two-thirds of the spices we tested did not have concerning levels of heavy metals,” Akinleye says. “So we know spices don’t have to have worrisome amounts of lead or arsenic or any other heavy metal.”