As You Sow, an organization that describes itself as “promoting environmental and social corporate responsibility” commissioned a lab to test levels of lead and cadmium in 42 chocolate products. They found a lot of lead and cadmium:
26 of the chocolate products (~62%) contain lead and/or cadmium at levels in which one serving exceeds the California safe harbor level for reproductive harm.
Lead is associated with neurological impairment, such as learning disabilities and lower IQ, even at low levels.
Cadmium has been linked to kidney, liver, and bone damage in humans.
From Food Safety News:
Some of the chocolate tested contained lead at levels up to 5.9 times California’s “safe harbor” level — or the maximum allowable daily limit — for reproductive harm, and found cadmium at levels up to 8.2 times the limit.
Polluted soil and air contaminates the cacao beans as they grow, are air dried, and processed. Pesticides, fertilizers, and leaded gasoline contaminate soil. The burning of fossil fuels and municipal waste pollute the air. Organic chocolate was found to have the same high levels of these heavy metals as nonorganic.
Eleanne van Vliet, As You Sow’s director of toxic chemicals research:
There also appears to be no clear pattern of brands affected as they span the range of chocolate on the market.