Air pollution from lead mines in twelfth-century Britain was as bad as it was during the Industrial Revolution and exactly maps the comings and goings of England’s Kings, a new world-first study has shown.
Climate change scientists, historians and archaeologists from the Universities of Nottingham, Harvard and Maine used ultra-high precision laser technology to analyse the contents of an 800-year-old section of ice, part of a 72-metre-long core bored from a glacier in the Swiss-Italian Alps.
The research shows how traces of lead pollution from mines in the United Kingdom, in particular the Peak District, directly mirror historical ‘parchment roll’ records of lead production in the region between 1170 and 1216. The work was led by Nottingham’s Christopher Loveluck and is now published in Antiquity.
The ice core was bored out of the Colle Gnifetti glacier in the Monte Rosa Massif on the Swiss-Italian border in 2013. It is super-compacted and is made up of invisible layers containing chemical elements that form an annual chemical fingerprint, analogous to an annual tree ring. Cutting edge atmospheric modelling shows that these elements were deposited by the winds coming from the north west carrying dust and pollution from the UK.
The core is the subject of an ongoing collaborative project led by Paul Mayewski of the Climate Change Institute-University of Maine and Michael McCormick, Department of History, Harvard University. It is yielding an unparalleled year-by-year picture of over 2,000 years of climate-related, environmental, economic and political history.
Heavy metal detecting
In a world-first, the new research shows that the annual pollution levels reaching the Alps between 1170 and 1216 mirror the royal records of annual lead and silver production in England, and the impact of wars and major building projects by the Angevin kings, Henry II, Richard the Lionheart and John. This provides the only instance to date when the environmental impact of a medieval macro-economy, and political influences upon it, have been fully demonstrable on an annual basis (with over 100 measurements of lead pollution per year between 1170 and 1220).
People have mined lead-silver ores for centuries to use in coins, roofs, water pipes and even paint but it is a toxic metal that, even at very low levels of exposure, can reduce brain function and result in lifelong health complications. The impact of such long-term pollution on our lived environment at a western European level has barely been made clear. Until now.
The laser technique used to analyse the annual layers in an ice core for the first time is called Laser Ablation Inductively Coupled Plasma Mass Spectrometry. It allows highly sensitive measurement of the presence of chemical elements like lead and can take 50,000 readings in a single metre of ice core.
The team’s intensive work on a specific portion of the core laid down in the middle ages shows that the Colle Gnifetti glacier offers up an unprecedented detailed timeline of the environmental impact of British lead mining and smelting on western Europe. It exactly maps the calendar of historical events that occurred during the Angevin Empire from 1170-1216, from the death of Thomas Becket to Magna Carta – showing how lead production fell during times of war and rebellion, and in interregnums between monarchs.
Having established from atmospheric-modelling, archaeological and historical research that the Alpine lead pollution signal was predominantly British at the highest point of medieval pollution in the later twelfth century, team deliberately chose the section of the core that dated from c. 1167 to 1220 so they could explore any matches between lead content in the ice with the annual historical records of lead production in the English taxation records, known as the Pipe Rolls, for the Anglo-Norman (Angevin) Kings, Henry II, Richard the Lionheart and John, housed in the National Archives at Kew.
“Our work on the Colle Gnifetti glacier has shown the true potential of this fantastic new laser technique, in conjunction with historical and archaeological records,” explains Professor Christopher Loveluck. “The correlation between evidence of lead production in Britain in the ice core deposits and the tax paid on lead mines is astonishing! We see direct associations between production levels and the workings of government at the time, for example, lead taxation and lead production plummets in the year when a king dies before they are succeeded by another one. This is because medieval governments shut down in the interregnum. The ice core shows precisely when one king died, and lead production fell and then rose again with the next monarch. We can see the deaths of King Henry II, Richard Lionheart and King John there in the ancient ice.
“Importantly, our results show that the twelfth century has the same levels of lead pollution as we see in the mid seventeenth century and even in 1890 so our notions of atmospheric pollution starting in the industrial revolution are wrong. Then the ice core shows a rise with lead petrol in the motor car, and a big fall when lead is banned from fuel in the 1970s.
“For us here in Nottingham, the big story is that 75% of that record in the ice core in the Alps is a direct mirror of Peak District lead production. In that period, the biggest mining areas in Britain were around Wirksworth and Castleton in the Peak District and the mine of Carlisle which was actually based in the central Pennines.”
Professor Michael McCormick, “It proves largely that those ancient hand-inscribed British historical records, the Pipe Rolls, are right about the patterns of lead production. Those particulates from all those years ago embedded deep in the ice core are our proof, thanks to this new technology.”
Assistant Professor Alexander More also commented “By shining a laser on centuries-old ice we’ve learned to read glaciers as we read a book. We’re doing both, and much more, to shed light on the economic and health implications of such extensive lead pollution in our environment.”
The next big project for this international interdisciplinary research team is to look at ultra-high-resolution climate change. Alongside the pollution evidence, the ice also contains evidence of short- and longer-term climate events and the team hopes to be able to paint a much more detailed picture of volcanic eruptions and weather events dating back 2000 years.
Top Image: Iron smelting in Middle-Age, from “De Re Metallica” by Georgius Agricola, 1556