Interior of the cathedral in Seville (Photo: N. Selin)
In one of our last trips before the COVID-19 pandemic, we visited southern Spain. We joined a crowded line of tourists walking through the famous cathedral in Seville, marveling at the ornate silver objects on display. As we were admiring the silver, we also could not help thinking about mercury, and that was not just because we were still putting the finishing touches on the Mercury Stories book. Mercury is deeply connected to both silver production and history in that area of southern Spain, which has historically been the world’s largest producer of mercury extracted from cinnabar.
Chapter 3 tells the story of global mercury cycling in both society and the environment, and how those two processes must be examined together. We begin the chapter by introducing the history of silver amalgamation. In 1554, the Spanish merchant Bartolomé de Medina developed the patio process, which uses mercury in the process of extracting silver from the mined ore. This patio process made mines in the Americas, which contained large amounts of low-quality silver ore, much more profitable for Spanish colonialists, and this societal flow and use of mercury powered Spanish colonialization of the Americas and reshaped international trade and commerce between Europe and the Americas in the 1500s and 1600s.
Cinnabar rock from the area of Almadén (Photo: H. Selin)
The fate of all the mercury used in the silver mining process in the Americas in the 16th and 17th centuries is still unknown – some estimates put that total at more than 100,000 tonnes of mercury. Some scientists have argued that this mercury still cycles globally in the environment in substantial quantities today; others point to evidence from deposits in sediments and argue that this mercury mostly remained where it was used. Mercury is discharged into the environment in many different forms, and can also change form as it cycles between the atmosphere, oceans, and land. Some mercury is transformed into highly toxic methylmercury through bacterial process in aquatic environments, where it accumulates in fish and marine mammals, posing risks to seafood consumers.
In Chapter 3, we discuss how mercury can continue to cycle between the atmosphere, oceans, and land for decades and even centuries. The mercury depositing in ecosystems today comes not only from modern-day sources, but also from the historical legacy of past mercury use and emissions. It is possible that some of the methylmercury in your last portion of tuna sushi originates from other forms of mercury that was emitted hundreds of years ago! It is important to note, though, that methylmercury concentrations in fish can respond quickly to changes in deposition. Thus, reductions in mercury emissions today can lead to positive impacts both now and long in the future.
While the exact environmental fate of colonial-era mercury use in the Americas is still scientifically contested, its human impact and societal legacy are undeniable. Large quantities of mercury moved across the world on ships, fueling the accumulation of wealth by some and leading to grave harms to many others. A few days after our visit to the cathedral in Seville, we journeyed to Almadén, the mine where roughly one-third of all the world’s mined mercury – over a quarter of a million tonnes -- originated over its 2000-year history. Having closed in 2002, this mine is now a UNESCO World Heritage site, together with another former large mercury mine in Idrija, Slovenia (which we have also visited – twice!).
Sign at the entrance to Almadén, Spain (Photo: H. Selin)
Almadén is only three hours by car from Seville, but the life experiences of the people who for centuries worked down in the mine were worlds away from those with great wealth who accumulated the shiny silver objects now on display in the cathedral in Seville. The impacts of mercury exposure to miners – in Almadén, in Idrija, and in other mercury mines – were well-known five hundred years ago. The toll that extracting mercury took on the mine workers is covered in detail in the museum located in Almadén’s former hospital. Over time, these workers included enslaved people as far back as Roman times, inmates from the prison strategically located next to the mine with direct access to the shafts, and (more recently) salaried employees.
There was also much human suffering in mercury mining in the Americas. In the mercury mine in Huancavelica, Peru, in the 1500s, the Spanish introduced a system called the mita to force Indian laborers into the mercury mine, which devastated indigenous populations through a combination of high mortality rates in mining and flight of potential laborers to avoid conscription. Work in the mine, even for a short time, was often a death sentence. In addition, many forced workers in silver and gold mining in the Americas and elsewhere were exposed to high levels of mercury during extraction processes. Dangerous mercury exposure continues today in the artisanal and small-scale gold mining sector, which we discuss further in chapter 7.
We argue in Chapter 3 that to fully understand the fate of mercury and its impact on human health, researchers and others have to account for its societal movements as well as its environmental behavior. It is important to take a perspective that goes beyond typical scientific analysis focused on biological, geological, and chemical processes in the environment. We call this perspective human-technical-environmental cycling. A systems perspective such as the HTE framework that we set out in chapter 2 helps us do just that – illustrating not only how mercury cycles in the environment, but also its interactions with humans and technologies in the context of institutions and knowledge.
We end Chapter 3 with a discussion of the Minamata Convention and its provisions. The Minamata Convention takes a life-cycle approach to addressing mercury-related challenges – addressing not only its emissions and releases to the environment, but also its use and trade across borders. A life-cycle approach to mercury is necessary, but challenging – in chapter 10, we evaluate some of the lessons for mercury policy that we draw from the analysis in the book. Stay tuned!