European Union should be 2.3 micrograms per kilogram (ppm)

1500 ppb for cocoa powder), established by the FAO/WHO in this type of food. (IVAN DARIO, 2015)

Determination of the concentration of metals in cocoa beans in the Bella Agricultural Cooperative in the Province of Leoncio Prado-Huánuco and possible consequences of health risks (thesis. 2019)

As above indicated by Prof. Omar Tirado, the European Union typically establishes international guidelines for cocoa beans (in the case of heavy metals), so you can take a look. The most significant heavy metal in cocoa is cadmium, and there is extensive research in American and African cocoa-producing nations. Here are some literature tittles you might find useful:

1.Development of validation methods to determine cadmium in cocoa almond from the beans by ICP-MS and ICP-OES

2. DETERMINATION OF HEAVY METALS IN COCOA BEANS FROM SOME MAJOR COCOA GROWING REGIONS IN GHANA

3.NUTRIENT STOCKS,NUTRIENT CYCLING, AND SOIL CHANGES IN COCOA ECOSYSTEMS:A REVIEW

4.Cadmium uptake by cocoa trees in agroforestry and monoculture systems under conventional and organic management

5.Multielemental fingerprinting and geographic traceability of Theobroma cacao beans and cocoa products

6.Determination of the Provenance of Cocoa by Soil Protolith Ages and Assessment of Anthropogenic Lead Contamination by Pb/Nd and Lead Isotope Ratios

7.Heavy metal accumulation in leaves and beans of cacao (Theobroma cacao L.) in major cacao growing regions in Peru

8.Soil properties and agronomic factors affecting cadmium concentrations in cacao beans: A nationwide survey in Ecuador

9.The elemental composition of chocolates is related to cacao content and origin: A multi-element fingerprinting analysis of single origin chocolates

10.Concentration of cadmium in cacao beans and its relationship with soil cadmium in southern Ecuador

11.Soil cadmium uptake by cocoa in Honduras

12.The mobility and bioavailability of trace metals in tropical soils: A review

And many others, good luck~