Lead in bones: a cautionary tale

An attempt has been made to assess the degree to which past populations were exposed to lead by measuring the concentration of lead in bones from archaeological sites. Preliminary analysis of the results seemed to indicate that there had been a great variation in exposure to lead in the past and that, in some cases, lead might have made a significant contribution to the morbidity or mortality of the population. One persistent problem in interpreting the results has been to assess the degree to which the bones had absorbed lead from the soil. A priori reasoning led me to believe that, at sites where the bones were well preserved, little exchange of lead would have occurred. When I used physical methods to localize the lead within bones or teeth, however, it became clear that most of the lead was located on the surfaces, and this could only be explained by post-mortem absorption. At two sites I have found a significant correlation between the concentrations of lead in bones and soil taken from the same grave; this is further evidence for lead uptake after death. From the later studies it seems that exposure to lead in the past can only be determined by a careful prospective study taking random samples of bone and soil from sites, which can be dated to within narrow limits.