Mercury | Vermilion: The life-threatening red of the Maya

Reproduction of a stele at the entrance to the Mayan city of Toninga in the typical shade of red Photo: imago/VWPics For the Maya of the classical and postclassic periods, that is, between 250 CE and the conquest by Spain, this world and the afterlife were linked. The gods were not distant from people, but rather influenced their lives - and deaths. They had to be appeased and honored and the numerous pyramids, but also many small steles and cult objects, served this purpose. They all liked to be painted red, because red was the color of the gods, life and blood. The downside: The red color was obtained from cinnabar, which is chemically speaking from the poisonous mercury sulfide (HgS).

It was previously assumed that cinnabar was particularly used in the Classic Maya period between 250 and 900. At that time, the cities and cult centers were concentrated in southern Mexico as well as in Guatemala and Honduras - these included Tikal, Quiriguá, Kaminaljuyú, Copán and Caracol.

As the Maya moved further north with a new focus on Yucatán, they also took their beliefs with them. Contrary to previous assumptions, the use of cinnabar continued on the peninsula that today belongs to Mexico. This is the conclusion reached by a group of researchers from Auburn University in Alabama, led by Matthew Waters, who analyzed two lakes, Cobá in eastern Yucatán and Cenote Xcach in the western part of the peninsula. The Maya were “fascinated by mercury both in its elemental form and as cinnabar, which they used as a pigment in burials and to decorate ceramics and buildings,” writes Waters in the journal “Science Advances.”

Plants, snails and mosquitoes could no longer be found in the lakes.

The researchers took core samples from the sediment layers of the two lakes. These can be determined in time and thus allow the chronological sequence of mercury concentrations in the environment to be followed. The period examined was between 200 BC. C.E. to the present. Through erosion, the mercury found its way into the lakes, which are important for the water supply of the two cities. Cobá had between 50,000 and 90,000 inhabitants, while Cenote Xchach was located near a city whose ruins have hardly been explored and whose population is unclear. The researchers found the highest level of 2.3 micrograms per gram (ppm) of sediment for Lake Cobá in the 3rd century. In Cenote Xcach the values ​​were similarly high during this period, then fell sharply, only to rise again after 530. An average of 8.4 ppm was measured here and the peak value reached 18 ppm in 720. Current occupational health and safety regulations allow a maximum limit of one ppm and speak of health-threatening concentrations above two ppm. However, these values ​​refer to mercury vapor in the air.

The researchers were able to monitor the biological activity of both lakes. As mercury concentrations increased, it decreased and eventually collapsed. Plants, snails and mosquitoes could no longer be detected. The research group suspects that the Maya living around the lakes were exposed to mercury through consuming water and proteins from the lakes. Mercury in the vermilion form is less toxic in the gastrointestinal tract than inhaling vapors. But taking it for long periods of time can affect the digestive tract. If consumed continuously, the kidneys, nervous system, teeth and gums will also be damaged. However, the research report also emphasizes that further studies on skeletons are needed to confirm that people were actually exposed to mercury.

As early as 2022, an Australian research group published a study that looked at the water reservoirs of the famous Mayan site of Tikal. The basin in the center, which was surrounded by temples and palaces of the elite, had the highest mercury concentrations. The peak value was 17 ppm. Mercury poisoning, along with droughts and wars, may have caused the collapse of the Mayan culture. But further research is needed to confirm this assumption.

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