Uptake and in-vitro bioaccessibility of toxic metals in cocoa beans: Human health risks

Cocoa-growing areas in Ghana have experienced a rise in mining activities affecting cocoa cultivation and increased concentrations of potentially toxic metals in the soil, which can accumulate in cocoa beans. This study evaluated potential toxic metal contamination in cocoa beans and soils from cocoa farms in mining and non-mining areas in Ghana. We used X-ray fluorescence and an ICP-MS to determine metal concentrations, and a Zeeman mercury analyzer to determine mercury. The farm soils exhibited a pH range of 4.08 – 6.86, electrical conductivity between 29.16 and 870.50 μS/cm, and soil organic matter content ranging from 4.78 to 7.38%. Generally, metal concentrations in the soil were within the Canadian Soil Quality Guidelines for Agricultural soils, Dutch Target and Intervention Values, and the world average world soil for unpolluted soils but varied between study areas. Arsenic (1.20 – 1.33 mg/kg), cadmium (2.68 – 3.16 mg/kg), chromium (9.31—11.73 mg/kg), copper (59.69—70.88 mg/kg), mercury (0.008—0.017 mg/kg), manganese (18.90—23.68 mg/kg), nickel (10.19—11.76 mg/kg), lead (1.71—1.86 mg/kg), and zinc (80.20—87.34 mg/kg) were found in cocoa beans. The mean bioaccessibility for metals in cocoa beans, except for As, Cu, and Pb, was greater than 60%. Cadmium had high contamination in soil; geoaccumulation (Igeo > 3), contamination factor (CF > 18), and enrichment factor (EF > 70.21), while Cu and Zn had high bioaccumulation (BF > 4). The target hazard quotient value for metals in all farms showed no potential health risk (THQ < 1) for both children and adult consumers. The cocoa beans produced have low risk upon consumption.