There are any number of factors that contribute to the demise of an entire civilization, like the collapse of the Roman Empire circa 476 AD. The empire’s slow decline is typically attributed to barbarian invasions, failed military campaigns, economic challenges, government corruption, and an over-reliance on slave labor, among other factors. But it’s also been suggested that the toxic effects of lead poisoning on increasingly erratic rulers may also have contribute to its demise—a debate that has been revisited in a new Reactions video from the American Chemical Society.
Lead has a number of properties that make it attractive for practical use. It’s cheap, widely available, corrosion resistant when exposed to air and water, has a low melting point, and is highly malleable, which means it’s easy to fashion into a wide range of products. But lead is also highly toxic if it finds its way into the human body, which is why we use it far less these days compared to even 100 years ago. Common symptoms of lead poisoning include anemia, nerve disorders, memory loss, inability to concentrate, and even infertility. Lead exposure may also be a factor in malaria, rickets, gout, and periodontal disease.
Since 1943, scientists have known that lead can have adverse effects on neurological development in children, leading to behavioral problems and lowered intelligence. That’s because it can easily replace calcium. Calcium is how neurons in the brain communicate, and if lead replaces it, there is either too little communication among neurons, or too much. This can cause erratic mood swings, or difficulty processing information, for instance.