The distribution of lead within ancient and modern human teeth: implications for long-term and historical exposure monitoring.

The preservation of lead within human tissue makes it possible to monitor long-term exposure to the element and to model changing sources of lead pollution throughout the lifetime of an individual. Dental tissues have recently been shown to be particularly useful for this purpose. Enamel, for instance, forms at known stages of life and is chemically stable in vivo whereas dentine is remodelled in a predictable fashion. The relative stability of enamel is reflected in its excellent post-mortem preservation. This raises the possibility of using historical or archaeological material to reconstruct long-term trends and establish baseline data relating to exposure among pre-industrial or even prehistoric populations. The use of archaeological material is currently problematic, however, because of the site-specific nature of diagenesis and incomplete understanding of its chemistry, particularly in respect of lead uptake into dental tissue from the burial environment. A detailed study of lead distribution within both ancient and modern human teeth is presented. Conclusions are drawn on the pattern of lead distribution resulting from tissue formation and the manner of its alteration in the burial environment. In particular, attention is drawn to a consistent enrichment of lead within the outer 30 microns of the enamel of both ancient and modern teeth which appears to be unrelated to diagenesis. The implications for current approaches to long-term monitoring and for the reconstruction of historical and archaeological exposure patterns are discussed.