However, only two samples out of 30 exceeded US Food and Drug Administration recommendations for lead, scientists said.
In the study published in American Chemical Society's Journal of Agricultural and Food Chemistry, researchers noted that chocolate has many potential health benefits due to the high levels of flavonoids and antioxidants in its star ingredient, cocoa.
But unwanted components can make their way into the delectable treat, researchers said.
Past studies have shown that crops can take up lead and cadmium, two naturally occurring metals. Lead can cause abdominal pain, headaches and anemia in adults. In children, it can cause behavioural changes and language delay, among other problems.
Cadmium can cause damage to several organs. It also has estrogen-like effects and disrupts some hormones.
Researchers set out to analyze commercial samples for the metals. They tested 30 milk chocolates, dark and white chocolate products bought in Brazil. Most were Brazilian brands, some of which are also sold in US.
They found that dark chocolates had the highest amounts of lead and cadmium, but all levels fell below maximum consumption limits from Brazil, the European Union and the World Health Organization.
The US FDA, however, recommends that the level of lead in candy should not exceed 100 nanogrammes per gram (ng/g) of candy; two samples topped this threshold by about 30 to 40 ng/g.
The researchers pointed out that only a fraction of lead or cadmium would absorb into a person's bloodstream, but the levels they found in dark chocolate were still concerning.

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