A recent paper from the International Journal of Osteoarchaeology, revealed that the oldest victims of mercury poisoning was buried in Spain and Portugal. While the exposure to mercury today happens due to the intake of certain fish or shellfish, the levels are low. Researchers were able to compare bones from 23 different sites belonging to 370 individuals that inhabited the area over a period of 5,000 years. The remains showed mercury levels of up to 400 parts per million (ppm), much higher than the normal level of 1-2 ppm.
    The question then is where this poisoning came from? The answer lies in one of the main artistic elements of the time, cinnabar powder. This fine powder, when turned into a pigment, is responsible for the color known as 'Pompeian red' or 'Vermillion'. This pigment is often used in tombs from this period in southern Portugal and Andalusia, where it is used to decorate figurines and paint megalithic chambers. As the Copper Age drew to a close, around 2200 BCE, the use of cinnabar decreased significantly, according to the study.

Edited from EurekAlert! (15 November 2021), ScienceAlert (18 November 2021)