Here is a chocolate maker actively involved in the fundamental questions of lead and cadmium content in the products they create. They also take is several steps further to find the points at which toxic levels of heavy metals could be introduced in to the raw product, the cacao orchards, the length of fermentation process (fungi being heroes of balancing toxins and binding them in ways favorable to humans). I would also add transportation and especially processing equipment. Having sold titanium steel cookware for many years due to it's inert qualities, I'm aware that lower quality metals can deteriorate and find their way into the processing.
Chocosol as an experiement in "Safe Chocolate"
Cacao that is certified lab-tested so you can feel safe. 
Cacao or cocoa sourced from regions with fertile, organic soil and no contamination from nearby industry, along with the removal of a high degree of the shells (winnowing) provides greater safety in the levels of lead and cadmium found in samples of the nibs.
In May, 2022 ChocoSol sent a 100% cacao chocolate bar to a lab for heavy metal testing. Due to customer requests, they wanted to be able to reply to customers with specific, quantitative lab results on par with the great attention to the health and ecology of the regenerative agricultural and forest garden polyculture approaches the cacao, coffee, and vanilla are sourced from.
In terms of lead, mercury, arsenic, and aflatoxins, the results show the source cacao was below the "minimum detection levels" (MDL), lower than 10% of recommended levels. Cadmium was 32% of the recommended maximum level. These levels are far lower than the safest recommendations made in the "consumer report" you may have read.
The FDA, CFIA, EU and FAO standards quite similar, but there are some differences worth exploring in order to provide more exact comparisons.
Additional questions being studied by Chocosol:
1) What is the difference between plantation style vs. forest garden cacao growing in polycultures and semi-wild environments?
2) What is the effect of longer fermentation on heavy metals that may naturally be contained in the seeds? To test this, we would select 2-3 regions where we could acquire similar beans from similar soils, and test the difference between cacao that fermented and dried for 3 days and cacao that was fermented for 7-8 days. The theory is that the fermentation process, which is done for fine flavor-aroma chocolate and not as much in industrial cacao, might also help with reducing the heavy-meatal through the acidic fermentation and leeching of the beans.
3) As an approach to food safety and quality, what are the variations by origin/region in regards to terroir? Independent testing of cacao from various origins to establish healthy baselines for safety standards.