The heavy metals of dark chocolate featured in "Bittersweet Composition".

“Bittersweet Composition” is the new addition to Carlo Marcucci’s “Chemical Still Life” series since “Fragola Amara”in 2007. In this latest work, the artists tackles the subject of lead and cadmium contamination in dark chocolate. For this work, the artist chose a selection of chocolate bars purchased at local grocery stores (Trader Joe's 85% Dark Chocolate Lover's bar, Theo Organic 70% Pure Dark Cocoa bar, Lindt Excellence 85% Dark Chocolate, Chocolove 88% Extreme Dark Chocolate sample, and Alter Eco Organic 85% Dark Chocolate Classic Blackout bar) and one cocoa powder (Starbucks Hot Cocoa Classic).

According to recent chemical analysis, performed by Consumer Report utilizing the California Proposition 65 Maximum Allowable Dose Levels (MADL), two heavy metals where commonly found in almost all chocolate samples (regardless if they were organic or non-organic). For example some samples like Perugina 85% Premium Dark Chocolate, were found tp be 539% over MADL limits for lead, and samples for Pascha Organic 85% Very Dark Dark Chocolate were 253% over the limits for cadmium.

As per the chocolate selection used in this artwork, the Trader Joe's brand had 127% over MADL levels for lead and 229% above the MADL levels for cadmium. Theo Organic brand had 120% above the MADL levels for lead and 142% for cadmium. The Lindt sample had 166% above MADL levels for lead and 80% for cadmium. Chocolove sample (depicted here without its wrapper) had 240% levels for lead and 83% for cadmium. The Alter Eco sample found 204% levels for cadmium and the Starbucks powder sample had 159% MADL readings for lead.

Continuous long-term exposure to even small amounts of heavy metals can lead to a variety of health problems, especially for pregnant women and young children because the metals can cause developmental and brain problems. Frequent exposure to lead in adults can lead to nervous system issues, hypertension, immune system suppression, kidney damage, and reproductive harm.

Researchers believe that cacao plants tend to naturally absorb cadmium stored in the surrounding soil, with the metal accumulating in the beans as the tree grows older (similar to how heavy metals contaminate some other foods).

Lead contamination seems to happen after the beans are harvested, where the metal is typically found on the outer shell of the cocoa bean, and not in the bean itself. Researchers found lead levels to be low soon after the beans were picked and removed from pods, but levels increased as the beans dried in the sun for days - maybe due to exposure to lead-filled dust and dirt in the environment.