Friday, August 24, 2018

New studies on lead poisoning and Franklin's men

Tin of Ox Cheek Soup (Photo by Jeff Dickie)
It's one of the first things that many people still ask about the demise of the Franklin expedition -- wasn't it the lead in the tins that caused it? But now, after several recent studies shed some doubt on whether the "lead hypothesis" was the catch-all explanation of the tragedy, comes a broad and significant study -- whose co-authors include veteran Franklin researchers Anne Keenleyside and Doug Stenton -- that demonstrates that, in the end, this hypothesis turns out not to hold. However, there are still instances where lead exposure may have played a role, and as the picture clarifies it grows more complex. It's my personal view that, although the earlier lead hypothesis -- originally advanced in Owen Beattie and John Geiger's classic Frozen in Time -- no longer explains everything, it has led to some of the most fascinating and significant research on the health -- and thus the ultimate disposition -- of Franklin's men.

This new study, whose lead authors are Treena Swanton and  Tamara L. Varney, does what no other study has done before -- compare lead levels in the three individuals buried at Beechey (who died in the first winter) to remains from King William Island, which -- assuming that they date from after the desertion of "Erebus" and "Terror" -- date from at least two years further along in the expediton. If, as had been conjectured, these later remains showed signs of continued exposure and absorption of lead, then that would have demonstrated that the source of such exposure must have come during the expedition, and thus from sources on board ship, presumably the provisions consumed in this interval. And yet, using imagery that reveals the deep cortical microarchitecture within which lead would have been absorbed and stored, this new study shows that the patterns within the bone are very similar between individuals who died in both timeframes. There were, indeed, elevated levels of lead, but these were in parts of the bone that would have been formed prior to the expedition's departure in May of 1845.

And yet lead remains a factor, at least for some. By an interesting coincidence, another study appeared scarcely a week prior to this one; conducted by Lori D'Ortenzio, Michael Inskip, William Manton, and Simon Mays (Dr. Mays, it should be noted, was a co-author in two earlier and significant studies, both of which included William Battersby's work), looked at a strand of hair from the Greenwich skeleton, widely now believed to by that of Henry Duncan Spens ("Harry") Goodsir. Since this skeleton, brought back by Charles Francis Hall, was found on the southern coast of King William Island, it can safely be assumed to be part of the later timeline, and since the hair, even more so than bone, could show the changes in absorption over time, it was hoped that new insights might be gained from it. And yet, in many ways, it confirms the larger study; the lead isotope ratios were nearly identical to the bodies exhumed at Beechey, and although there was evidence of more recent absorption of lead, in this case it did not reach levels likely to cause clinical symptoms. It should be noted, though, that from the earlier studies of Keenleyside, Bertulli et. al. we know that at least some of the individuals whose skeletal remains were represented at NgLj-2 (the "Boat Place" at Erebus Bay) had lead levels as high as 223 micrograms per gram of dry bone. Further studies by Keenleyside suggested that blood levels as high as 1500 mcg per decilter of blood could be inferred; these individuals would almost certainly have been suffering from acute lead toxicity, and it may indeed have been the primary cause of death.

Why these few men -- just two to four of the estimated 11-13 skeletons in Keenleyside's study -- would have had such high levels of lead remains unexplained. Recent DNA analysis, which shows that the number 13 is the most accurate, and that Erebus Bay sites collectively represent at least 21 individuals, may make these few even more "outliers" from the rest -- but they still remind us that lead was a factor for some. For the rest, it now seems clear, background levels of exposure from before they sailed with Franklin were simply much higher than we'd realized, and despite some continued exposure -- variable, certainly -- during the expedition, the original lead hypothesis no longer explains the eventual demise of the expedition as a whole.

No comments:

Post a Comment