Sunday, November 28

Oldest evidence of mercury poisoning – deadly high values ​​5,000 years ago due to cinnabar pigments containing mercury –

Deadly dye: The production and use of the coveted vermilion lead to severe mercury poisoning around 5,000 years ago, as analyzes of remains from this time have now shown. Some of the dead buried in Copper Age Spain had mercury levels in excess of 400 ppm in their bones – enough to cause serious poisoning. The source of the cinnabar was one of the largest cinnabar mines in early history in the Spanish Almaden.

If mercury gets into the body, it blocks enzymes, disrupts the nervous system and can lead to serious health damage due to a gradual accumulation in the body. Today there are therefore strict limit values ​​for the heavy metal. In the past, however, mercury was very popular: kings had ponds and fountains built with the “liquid silver”, and healers used it in ointments and tinctures.

Cinnabarite (red) from the Spanish Almaden mine.© Rob Lavinsky/, CC-by-sa 3.0

The use of mercury in the form of the mineral cinnabarite – cinnabar – was even more widespread. Because this mercury sulphide turns an intense red color when it is ground, it was a pigment in great demand around the world for thousands of years. The red mineral was used for cave art, the Maya used it to paint their houses and in many cultures the red dye was used in rituals and ceremonies.

Mercury in the bones

A study by Steven Emslie from the University of North Carolina and his colleagues has now revealed the consequences of cinnabar use in prehistory. They examined bone samples from 370 dead people from 23 archaeological sites in Spain and Portugal for their mercury content. The dead came from a period of around 5,000 years from the Neolithic through the Copper and Bronze Ages to antiquity.

The result: some of the dead had surprisingly high levels of mercury. In their bones, the concentrations were up to 400 parts per million (ppm), as the team reports. For comparison: The World Health Organization (WHO) regards values ​​from one to two ppm in hair samples as questionable. The examined dead must therefore have suffered acute and fatal mercury poisoning during their lifetime.

Dating showed that the dead most affected came from the Copper Age between 2900 and 2600 BC. This makes them the oldest documented cases of mercury poisoning in humans.

Poisoning from cinnabar mining

But where did the poison come from? The analyzes showed that the highest levels of poisoning occurred in deaths from the region in the south and central Spain. What the sites have in common is that they were closely connected to Almaden in central Spain via trade routes, as the researchers explain. There was one of the largest mining centers for cinnabar at the time, and the mercury-containing mineral was mined and processed there as early as the Neolithic Age.

“This suggests that the high levels of mercury in the prehistoric dead are probably closely linked to cinnabar mining and the use of this pigment in ritual practices,” say Emslie and his colleagues. “Even the mining of cinnabar and the associated grinding of the ore exposed people to mercury vapors and toxic dust. You must have absorbed considerable amounts of the heavy metal. “

Taken in ritual practices

However, the poisoning of some of the dead was so extreme that the scientists suspect another cause: Because the coveted dye was a symbol of high status and played an important role in rituals, the ground mercury mineral could even have been consumed intentionally at the time. Shamans may have atomized it or heated it during rituals to inhale the fumes. The powder could also have been mixed into ceremonial drinks.

“The social practices related to cinnabar were so widespread and intense that some people undoubtedly became acutely ill with mercury poisoning,” explain Emslie and his colleagues. At the same time, the cinnabar mining in Almaden probably led to water, soil and plants in the entire area being contaminated with mercury.

The mining of mercury minerals in Almaden continued for millennia: It was not until 2000 that the Spanish government closed the mines because mining was no longer profitable. Today Almaden is a UNESCO World Heritage Site. (International Journal of Osteoarchaeology, 2021; doi: 10.1002 / oa.3056)

Quelle: University of Seville

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