Scientists have discovered unusually high levels of mercury in human bones dating back 5,000 years, which is the first evidence of mercury poisoning. Daily Mail reported that the bones of around 370 people, estimated to have lived during the Late Neolithic and Copper Ages, were recovered in Spain and Portugal.

Analysis of the bones showed that the highest levels of mercury found were those who lived between 2900 and 2600 BC. The team led by the University of North Carolina Wilmington said that the poisoning was likely due to exposure to cinnabar, a mercury sulfide mineral historically used for art or consumed as a "magic" drug.

 High Levels of Mercury Found in 5,000-Year-Old Bones, Making it the Oldest of Its Kind
(Photo : Wikimedia Commons)
Mercury escaped from broken thermometer. Note that mercury droplet is a perfect wide angle lens and all lights used are reflected back at mercury surface. This image is taken from video "Mercury - an alien metal" at chemicum channel in Youtube.

First Evidence of Mercury Poisoning

Researchers collected the bones from 23 different sires in Spain and Portugal and analyzed the bones that lived about 5,000 years ago. According to Live Science, the analysis of the humerus bone showed that they contain unusually excessive ranges of mercury. They detect as much as 400 elements per million in some of the bones.

According to a press release from the university, this range is way beyond the 1 or 2 ppm the World Health Organization (WHO) deemed regular ranges in human hair.

Researchers said the unusually excessive amount of mercury is attributable to cinnabar, a poisonous mercury sulfide mineral with shiny purple color. It is traditionally used as paint pigments. But at the end of the Copper Age and early Bronze Age, the use of cinnabar has gradually declined.

One of the biggest cinnabar mines in the world is in Almadén, Spain. Ancient people have started mining cinnabar in the area since 7,000 years ago. Cinnabar was sought after at that time and was even traded and extensively used in various rituals and social practices.

Furthermore, tombs in Portugal and Andalusia used cinnabar powder to paint chambers, decorate figurines and even put on over the dead. Researchers hypothesize that ancient people could have accidentally inhaled or consumed large amounts of mercury from cinnabar used in rituals.

The study titled "The Use and Abuse of Cinnabar in Late Neolithic and Copper Age Iberia" was published in the International Journal of Osteoarchaeology. 

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Mercury Exposure Poses Major Public Health Concern

According to WHO, mercury exists in many forms in the environment: elemental, inorganic, or organic. Some people are exposed to inorganic forms of mercury through their occupation, while most people are exposed to mercury via their diet through the consumption of fish and shellfish.

Depending on their degree of toxicity, mercury exposure could adversely affect the nervous system, as well as the digestive and immune systems. WHO considers mercury as one of the top ten chemicals or group of chemicals that pose a great threat to public health.

On the other hand, human activity is the main cause of mercury release, especially coal-fired power plants and even residential coal burning for heating and cooking. More so, waste incinerators, industrial processes, and mining of metals also contribute to mercury releases.

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