Cinnabar from Spain. It is the most common source ore for refining elemental mercury, and is the ... [+]
Mercury is one of the few metals found as silver-grey, native element mineral grains in nature, even if most deposits occur as cinnabar, a bright red mercuric sulfide.
In modern times, mercury is used primarily in the chemical industry and production of electronics. Mercury reacts with many other metals, and in the past was used to extract gold, silver and copper from ore rocks. It was also the main ingredient to produce a brilliant red or scarlet pigment named vermilion.
A recent paper published in the International Journal of Osteoarchaeology explores the complex relationship between humans and mercury over time.
Believed once to have medicinal properties, exposure to mercury can have serious toxic effects on humans, affecting the nervous, digestive, and immune systems, as well as the lungs, kidneys, skin, and eyes. The World Health Organization (WHO) currently considers mercury to be one of the top ten substances of greatest public health concern.
In the article, a team of 14 specialists in biology, chemistry, physical anthropology and archaeology associated with the University of Sevilla, have presented the results of the largest study ever carried out on the presence of mercury in human bone, with a sample of a total of 370 individuals from 50 tombs located in 23 archaeological sites in Spain and Portugal dating from Neolithic, Copper Age, Bronze Age and antiquity, thus encompassing 5,000 years of human history.
The results reveal that the highest levels of mercury exposure occurred at the beginning of the Copper Age, between 2900 and 2600 BC. In this period, the exploitation of large deposits of cinnabar found in Almadén and Idrija in central Spain increased considerably.
The exploitation of these deposits began in the Neolithic, 7,000 years ago. By the beginning of the Copper Age, around 5,000 years ago, the cinnabar became a product of great social value, with a character that was both sacred, esoteric and sumptuous. In tombs from this period discovered in southern Portugal and Andalusia, red cinnabar powder (and derived pigments) was used to paint rock art, decorate figurines and to spread it over the dead.
As a result, many people must have accidentally inhaled or consumed it, leading to unsuspected accumulations of mercury in their bodies. Levels of up to 400 parts per million (ppm) have been recorded in the bones of some of these individuals.
In fact, the levels detected in some subjects are so high that the study scientists do not rule out that cinnabar powder was deliberately consumed, by inhalation of vapors or even ingestion, for some ritual purpose.
Taking into account that the WHO currently considers that the normal level of mercury in human tissue should not be higher than 1 or 2 ppm, the data obtained reveal a high level of intoxication that must have severely affected the health of many of those people.
Mercury is still used in small scale (often illegal) mining activities in the Amazon forest, Central Africa, and Indonesia, with potentially disastrous effects on the environment and local population.
