Take a second to understand that CR used percentages to make sure their results sounded super bad. 
Baseline for lead was 0.5 micrograms per ounce, or 0.0000005 grams going by California's standard.
Toxic levels in children are around 10 mcg/dL or 0.00005 grams per liter. For adults, it's around 25 mcg/dL.
You'd need to be eating a lot of chocolate for it to be a genuine concern. 
Average adult blood volume is 5 liters, so 50 deciliters. You'd have to ingest nearly 950 ounces of Hershey's (the worst for lead) in one go to reach toxic levels. And that's assuming 100% absorption. 
So, sure, regulate allowable levels, but let's not go crazy here.