Beechey Island was where the Franklin Expedition over-wintered. The four graves were opened and the bodies examined in 1981, along with the adjoining rubbish tip.
The lead came from the food tins. The seams were simply butt-soldered, and not always very well at that (Quality control was unheard of) with the result that the seams were not always air-tight and that, in addition, the solder tended to be 'blobby' in places. The result was that many of the tins contained food that was not only polluted with lead but rotting as well.
Source:Owen Beattie & John Geiger,'Frozen in Time:The fate of the Franklin Expedition' Bloomsbury Publishing Ltd., London 1987.

There is also a novel built around Sir John Franklin, written by Sten Nadolny. I don't know whether there is an english translation, but the original title is 'Die Entdeckung der Langsamkeit'.

'Arctic Dreams', Barry Lopez,Bantam Books 1987 also has some interesting comments about the failure/failings of the Franklin Expedition.