It should be stressed, though, that the case remains circumstantial. The contents of the tin were enclosed for more than a century, which is a lot more time -- by at least a factor of 50 -- than any food actually eaten on the expedition. Furthermore, this tin was not one of the Goldner tins supplied to Franklin, so its method of manufacture and preservation may be significantly different, although closely contemporary. To really establish that this tin would have caused significant elevated lead levels if the soup had been consumed when intended, a totally different sort of experiment would have to be undertaken: you'd need to prepare a fresh batch of soup with the same basic qualities -- salinity, acidity, and so forth -- and then can it using identical materials and methods to those observed in this tin. Then, of course, you'd have to wait!
Amazingly, this is exactly what the researchers at McMaster plan to do. Having an actual tin in their possession is a plus -- the materials and qualities of the soup can be very closely replicated -- and they're planning to open and test their replica tin in one year. According to the McMaster website's article:
"With the lead levels confirmed, McMaster's Department of Anthropology will next make a batch of the ox cheek soup and can it using methods from the 1840s. Over the course of a year the cans will be opened and analyzed. Researchers will then be able to gauge how quickly lead leaches into soup rendering it lethal. Lead poisoning has long been considered a cause of death for the ill-fated explorers."
This is welcome news. I hope to be able to report in more detail on this current experiment, and will certainly pass along any results from the tests as they are announced.
None of this, of course, will completely resolve the issue of lead poisoning and the Franklin expedition. However, it should give us a far clearer picture both of the likely source of the lead, and the strength and extent of the contamination. William Battersby has argued that lead from the tins was insufficient to cause the very high levels found in bone samples, and used this argument to support his case that lead pipes in the ships' fresh-water distilling apparatus are a more likely culprit. A low level of lead leeching over one year would support his argument; a high level would make his claim less certain, but would not of course rule it out. Finally, whatever the source, the role of lead poisoning in the expedition's sad conclusion is itself a matter of some debate. The levels of lead in the bones from Ng-Lj-2 varied widely, with one or two individuals likely suffering from acute lead toxicity, while others had only moderately elevated levels. Did officers, because they were issued a larger ration of tinned food, end up with more lead? Whose bones were whose? And, aside from its physical effects, would the diminution of mental alacrity associated with lead poisoning be so great that it can be blamed as the sole, or primary cause of what, in hindsight, appear to be poor decisions? The debate will surely go on.
(photo courtesy of McMaster University Daily News)