Ancient Mayan cities were dangerously contaminated with mercury

Credit: Pixabay/CC0 public domain

The cities of the ancient Maya in Mesoamerica always impress. But beneath the ground surface lurks an unexpected danger: mercury pollution. In an overview article in Frontiers in Environmental SciencesResearchers conclude that this pollution is not modern: It is due to the frequent use of mercury and mercury-containing products by the Maya of the Classic Period, between 250 and 1100 CE. This pollution is so heavy in places that even today it poses a potential health risk to unwary archaeologists.

Lead author Dr. Duncan Cook, an associate professor of geography at Australia’s Catholic University, said: “Environmental mercury pollution is most commonly found in contemporary urban areas and industrial landscapes. Discovering mercury buried deep in soils and sediments in ancient Mayan cities is difficult to explain, until we consider the archeology of the region that tells us that the Maya used mercury for centuries.”

Ancient Anthropogenic Pollution

Here, for the first time, Cook and colleagues reviewed all data on mercury concentrations in soils and sediments at archaeological sites in the ancient Maya world. They show that at sites of the Classic period for which measurements are available – Chunchumil in present-day Mexico, Marco Gonzales, Chan b’i and Actuncan in Belize, La Corona, Tikal, Petén Itzá, Piedras Negras and Cancuén in Guatemala, Palmarejo in Honduras, and Cerén, a Mesoamerican ‘Pompeii’, in El Salvador – mercury pollution is everywhere except Chan b’i.

The concentrations range from 0.016 ppm at Actuncan to an extraordinary 17.16 ppm at Tikal. In comparison, the Toxic Effect Threshold (TET) for mercury in sediments is defined as 1 ppm.

Heavy users of mercury

What caused this prehistoric mercury pollution? The authors emphasize that sealed vessels filled with “elemental” (i.e., liquid) mercury have been found at several Maya sites, for example, Quiriqua in Guatemala, El Paraíso in Honduras and the former multi-ethnic megacity of Teotihucan in central Mexico. Elsewhere in the Maya region, archaeologists have found artifacts painted with mercury-containing paint, made primarily from the mineral cinnabar.

The authors conclude that the ancient Maya often used cinnabar and mercury-containing paints and powders for decoration. This mercury could then have leached from terraces, floor surfaces, walls and ceramics and then spread into the soil and water.

“For the Maya, objects can contain: ch’ulel, or soul power, which dwelt in blood. Therefore, the brilliant red pigment of cinnabar was an invaluable and sacred substance, but unbeknownst to them it was also deadly and its legacy persists in soils and sediments surrounding ancient Mayan sites,” said co-author Dr. Nicholas. Dunning, a professor at the University of Cincinnati.

Since mercury is rare in the limestone underlying much of the Maya region, they speculate that elemental mercury and cinnabar found at Maya sites may have originally been mined from known deposits on the northern and southern borders of the ancient Maya world, and imported to the cities by merchants.

Health Risks and the ‘Mayacene’

All this mercury would have been a health hazard to the ancient Maya: The effects of chronic mercury poisoning include, for example, damage to the central nervous system, kidneys and liver, causing tremors, impaired vision and hearing, paralysis and mental health problems. It is perhaps telling that one of Tikal’s last Maya rulers, Dark Sun, who reigned around 810 CE, is depicted in frescoes as pathologically obese. Obesity is a known effect of the metabolic syndrome, which can be caused by chronic mercury poisoning.

More research is needed to determine whether exposure to mercury played a role in larger sociocultural changes and trends in the Maya world, such as those towards the end of the Classic Period.

Co-author Dr. Tim Beach, a professor at the University of Texas at Austin, said: “We conclude that even the ancient Maya, who used very little metals, caused the concentrations of mercury in their environment to be greatly increased. This result is further evidence that there, just as we live in the ‘Anthropocene’ today, so was a ‘Mayan Anthropocene’ or ‘Mayacene.’ Metal contamination appears to have been the effect of human activity throughout history.”


Ancient Maya Reservoirs Contain Toxic Pollution: Study


More information:
Environmental heritage of pre-Columbian Mayan mercury, Frontiers in Environmental Sciences (2022). DOI: 10.3389/fenvs.2022.986119

Quote: Ancient Mayan Cities Were Dangerously Contaminated With Mercury (September 2022, Sept 23) Retrieved Sept. 23, 2022 from https://phys.org/news/2022-09-ancient-maya-cities-dangerously-contaminated.html

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