Leo,
If you have some of the older style of pink poly bags, that used a migratory
amine complex to induce moisture on the outer layers, you can get the amine
complex transferred to the PCB.  These were generally a heavier plastic and
had an "oily" feel to them.  Theoretically, the more modern pink poly bags
have the surfactant agent permanently bonded into the polymer matrix, and so
should not transfer any agents to the PCB.

I have not experienced any cases to date in which the modern pink poly bags
have caused a contamination problem.  Personally, I don't like them because
their function is dependent on surrounding ambient humidity levels, which is
not always constant.  For that reason, I prefer the metallized barrier (smoky
gray) ESD bags.

The only element which would realistically outgas from the poly bags would be
the plasticizer element, which is unlikely unless exposed to extreme
conditions (temperature, UV radiation).  If  you have assemblies which are so
sensitive to low levels of high molecular weight plasticizer materials, you
should be shipping them in a metal barrier (EMI bag rather than ESD) bag.

Hope this has been of some help.
Doug Pauls aka [log in to unmask]
Contamination Studies Laboratories
Chair, ESD Task Group