The inhabitants of the Roman Empire were exposed to a high amount of lead in the environment and this negatively impacted their cognitive development for centuries. Scientists of the Desert Research Institute (DRI) calculated the level of environmental pollution in Europe between the year 500 BC. C. and 600 AD. C. and measured the probable effects on the people who lived in European territory during that time. According to the study, lead contamination likely caused widespread cognitive decline and lowered the population’s IQ by several points.
Scientists can calculate the environmental pollution of an era through the particles that remain impregnated in the ice of the poles. As the environment has only accumulated ice sheets for millennia, climate information is trapped in gas bubbles and even organizes itself by strata. For example, with an ice core, it is possible to calculate carbon dioxide levels at the time of the dinosaurs and also pollution during the first human empires.
The work, published in Proceedings of the National Academy of Science (PNAS), used three Arctic ice cores to identify lead isotopes stored during the best years of the Roman Empire. Thanks to this, the researchers created a map of lead contamination in Europe, estimated its magnitude, the levels of the compound in the blood of the inhabitants and isolated the probable causes.
Silver mining operations were mainly responsible for contaminating Rome with substances dangerous to its inhabitants. For centuries, miners mined and smelted galena, a lead-rich mineral, to extract small portions of silver. According to historians, for every ounce of silver found in a galena, thousands of ounces of lead were released into the environment. In the 200-year heyday of the Roman Empire, more than 500 kilotons of lead were released into the atmosphere.
The consequences on the human body due to metal contamination have been widely recorded. The list includes infertility, anemia, cardiovascular diseases and even cancer. In the 20th century, the peak of lead contamination was reached, leading to the banning of the component in different fields. After decades of studies, today it is concluded that, in children, a A blood lead level of 3.5 micrograms per deciliter leads to a reduced intelligence quotient (IQ) and a decrease in your ability to concentrate.
The precedent of IQ decline due to lead levels in the 20th century helped DRI scientists estimate the decline in IQ of the European population during the period of the Pax Romana. The pollution from the Roman mining industry was not as serious as that caused by cars with leaded gasoline in 1970, but it was enough to affect new generations of inhabitants. Overall, the study concludes that IQ during the Roman Empire decreased between 2 and 3 points due to lead levels in the environment alone.
“A reduction in IQ of 2 to 3 points does not seem like much, but when applied to practically the entire European population, it is a big problem,” Nathan Chellman said.co-author of the study.
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