Re: Chocolate Lead Contamination Mystery


E. H. Burnham wrote:
> Science News reports that higher levels of lead contamination in
> chocolate products (averaging some 250ng/g) are a mystery which
> scientists have yet to solve:
> http://www.sciencenews.org/articles/20051105/food.asp. It seems that
> the cocoa bean itself contains relatively low levels -- 'among the
> lowest recorded of any foodstuff.' The husks are amazingly absorbant
> of Pb, and cocoa producing countries still use leaded gasoline; yet for
> husk contamination in cocoa to explain the anomaly, husks would have to
> constitute 104% of the cocoa -- a physical impossibility.
>
> Are we witnessing an alchemical transformation here?

Analytical chemists are often confronted with such situations. Once a
scientist from the former National Bureau of Standards was telling us
that the analysts were determining the elements present in human blood
by neutron activation analysis (which can detect very low amounts). The
results were puzzling. All of the blood samples analyzed had
significant molybdenum content (Mo is not present in human blood even
in traces, I'd guess). The cause was even more surprising. The
molybdenum was coming from the steel needle of the syringe while the
blood was drawn through it. Once the needle was substituted with
molybdenum was gone.

Believing in the results of those who have analyzed the chocolate for
lead content, chances are that Pb is coming during processing. As you
might know, roadside trees in the busy cities do have high lead content
in the leaves, according to survey in our country, so atmospheric +
land (say contaminated water) lead might be a contirbuting factor.

.

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