Mercury pollution may have posed a health risk to the ancient Maya—and it may continue to threaten archaeologists today, according to a recent paper in Frontiers in Environmental Science.
Alongside a team of researchers from the United States and the United Kingdom, lead author Duncan Cook, a geographer at the Australian Catholic University, analyzed mercury levels from ten Maya dig sites and their surroundings, per Science Alert’s Mike McRae.
“Mercury pollution in the environment is usually found in contemporary urban areas and industrial landscapes,” says Cook in a statement from the research team. “Discovering mercury buried deep in soils and sediments in ancient Maya cities is difficult to explain, until we begin to consider the archaeology of the region which tells us that the Maya were using mercury for centuries.”
Mercury levels under 1 part per million are not considered toxic, and some of the dig sites had levels below this threshold: For example, Actuncan (in Belize) had levels of 0.016 parts per million. But at other sites, mercury concentrations were far higher. In the ancient Maya city of Tikal, in modern-day Guatemala, they reached 17.16 parts per million.
The team concluded that the Maya used cinnabar, a bright red mineral containing mercury, for decorative paints and powders that served ceremonial and religious purposes. The mercury from cinnabar-coated surfaces, like walls and floors, eventually contaminated the local water supply and soil.
In the statement, study co-author and University of Cincinnati geologist Nicholas Dunning says the Maya believed cinnabar contained ch’ulel (“soul force”).
“[T]he brilliant red pigment of cinnabar was an invaluable and sacred substance,” says Dunning, “but unbeknownst to them it was also deadly and its legacy persists in soils and sediments around ancient Maya sites.”
The health effects of chronic mercury poisoning, which may have impacted the ancient Maya, include tremors, weakened vision and hearing, and paralysis, among other symptoms.
Dunning tells Gizmodo’s Isaac Schultz that archaeologists have yet to look for mercury in the skeletal remains of Maya burial sites. Cinnabar powder was often sprinkled all over the remains of royals and elites, and it may have seeped into their bones, which he says would complicate that kind of research.
For future research at Maya dig sites, the study authors recommend taking precautions, such as mitigation techniques and protective gear, to keep archaeologists safe.
“This result is yet more evidence that just like we live today in the ‘Anthropocene,’ there also was a ‘Maya Anthropocene’ or ‘Mayacene,’” says study co-author Timothy Beach, a geographer at the University of Texas, in the statement. “Metal contamination seems to have been [an] effect of human activity through history.”