The primary components for the 5c 1847 are - Calcium carbonate, Lead sulfide, and lead sesquioxide (red lead)
http://chronicle.uspcs.org/pdf/Chronicle_252/21674.pdf

That may not come through, as the articles after a certain date are members only.

Printing inks would of course vary a lot from pen inks, as the properties need to be a lot different.

Do you think they had any concerns about lead poisoning when they licked that Ben Franklin stamp?

I was also at the 2006 World Stamp Expo in D.C. Drove down to the APS in Richmond last year. I used to collect quite a bit more. Now I usually buy Olympic related postal covers (1960 Italian set, 1968 US Trials set) to get signed by athletes.

Probably no concern at all. What with hats made with mercury, clothes dyed with arsenic and most of it flammable they had other concerns. Which didn't really bother the wearers as much as the people making the stuff.

Washington was amazing, as was the display for Atlanta in 1996. Seeing the actual letters inviting countries to the first Olympics and a lot of similar stuff was very interesting. And totally changed my perspective on what made for an "important" collectible.