Helene Hoffmann

Next‐generation ice core technology reveals true minimum natural levels of lead (Pb) in the atmosphere: Insights from the Black Death

Abstract Contrary to widespread assumptions, next‐generation high (annual to multiannual) and ultra‐high (subannual) resolution analyses of an Alpine glacier reveal that true historical minimum natural levels of lead in the atmosphere occurred only once in the last ~2000 years. During the Black Death pandemic, demographic and economic collapse interrupted metal production and atmospheric lead dropped to undetectable levels. This finding challenges current government and industry understanding of preindustrial lead pollution and its potential implications for human health of children and adults worldwide. Available technology and geographic location have limited previous ice core investigations. We provide new high‐ (discrete, inductively coupled plasma mass spectrometry, ICP‐MS) and ultra‐high resolution (laser ablation inductively coupled plasma mass spectrometry, LA‐ICP‐MS) records of atmospheric lead deposition extracted from the high Alpine glacier Colle Gnifetti, in the Swiss‐Italian Alps. We show that contrary to the conventional wisdom, low levels at or approaching natural background occurred only in a single 4 year period in ~2000 years documented in the new ice core, during the Black Death (~1349–1353 C.E.), the most devastating pandemic in Eurasian history. Ultra‐high chronological resolution allows for the first time detailed and decisive comparison of the new glaciochemical data with historical records. Historical evidence shows that mining activity ceased upwind of the core site from ~1349 to 1353, while concurrently on the glacier lead (Pb) concentrations—dated by layer counting confirmed by radiocarbon dating—dropped to levels below detection, an order of magnitude beneath figures deemed low in earlier studies. Previous assumptions about preindustrial “natural” background lead levels in the atmosphere—and potential impacts on humans—have been misleading, with significant implications for current environmental, industrial, and public health policy, as well as for the history of human lead exposure. Trans‐disciplinary application of this new technology opens the door to new approaches to the study of the anthropogenic impact on past and present human health.

Size Matters: Radiocarbon Dates of <200 µg Ancient Collagen Samples with AixMICADAS and Its Gas Ion Source

Abstract For many of archaeology’s rarest and most enigmatic bone artifacts (e.g. human remains, bone ornaments, worked bone), the destruction of the 500 mg material necessary for direct accelerator mass spectrometry (AMS) dating on graphite targets would cause irreparable damage; therefore many have not been directly dated. The recently improved gas ion source of the MICADAS (MIni CArbon DAting System) offers a solution to this problem by measuring gaseous samples of 5–100 µg carbon at a level of precision not previously achieved with an AMS gas ion source. We present the results of the first comparison between “routine” graphite dates of ca. 1000 µg C (2–3 mg bone collagen) and dates from aliquots of gaseous samples of <100 µg C (<0.2 mg bone collagen), undertaken with the highest possible precision in mind. The experiment demonstrates the performance of the AixMICADAS in achieving reliable radiocarbon measurements from <0.2 mg collagen samples back to 40,000 14C BP. The technique has great implications for resolving chronological questions for key archaeological artifacts.

The Role of Historical Context in Understanding Past Climate, Pollution and Health Data in Trans‐disciplinary Studies: Reply to Comments on More et al., 2017

Abstract Understanding the context from which evidence emerges is of paramount importance in reaching robust conclusions in scientific inquiries. This is as true of the present as it is of the past. In a trans‐disciplinary study such as More et al. (2017, https://doi.org/10.1002/2017GH000064) and many others appearing in this and similar journals, a proper analysis of context demands the use of historical evidence. This includes demographic, epidemiological, and socio‐economic data—common in many studies of the impact of anthropogenic pollution on human health—and, as in this specific case, also geoarchaeological evidence. These records anchor climate and pollution data in the geographic and human circumstances of history, without which we lose a fundamental understanding of the data itself. This article addresses Hinkley (2018, https://doi.org/10.1002/2017GH000105) by highlighting the importance of context, focusing on the historical and archaeological evidence, and then discussing atmospheric deposition and circulation in the specific region of our study. Since many of the assertions in Bindler (2018, https://doi.org/10.1002/2018GH000135) are congruent with our findings and directly contradict Hinkley (2018), this reply refers to Bindler (2018), whenever appropriate, and indicates where our evidence diverges.