(Inside Science) -- Being poor in the Middle Ages was dreadful, but at least the poor weren't giving themselves lead poisoning.
A team of Danish chemists, analyzing the skeletons found in cemeteries in Denmark and Northern Germany, have found evidence of lead -- probably from the glaze on kitchenware -- in the bones. There possibly was enough lead to cause damage to the people's central nervous systems and adversely affect their intelligence or further incapacitate them.
The researchers, from the University of Southern Denmark in Odense, also found that the lead situation was worse among the skeletons found in what were urban areas in medieval times than in rural areas. Since people who lived in the cities and towns were usually more prosperous than those who lived in the countryside, it's likely the wealthier were more affected than the poor.
The researchers analyzed the skeletons of 283 people from six cemeteries, bodies of those who died from the 12th to the 14th centuries.
Besides lead, they also found mercury, another heavy metal poison, in the bones, but the distribution was more uniform and ubiquitous. Analysis looking for silver failed to find any at detection level.
Kaare Lund Rasmussen, associate professor of chemistry and the lead author of a paper published in the Journal of Archaeological Science: Reports, said the lead generally came from the glaze used on expensive pottery and tableware.
The potters would bake their dishes and cups in a kiln, and then apply a glaze containing lead oxide and re-fire the utensils, Rasmussen said. The glaze served aesthetic purposes, he said, the tableware was bright and beautiful.
"It looks really good," Rasmussen said, "colorful and shiny surfaces and easy to clean. Just use water and wipe it clean. It's like Teflon."
But, when they put salty or acidic food in the tableware, some of the glaze ends up in the food or drink.
The process also burned a lot of energy and was probably more expensive, another reason to think the wealthier in the land suffered more.
Lead also came from coins and stained-glass windows, and the lead tiles on roofs and was used in pewter, although that was mostly tin.
People without wealth couldn't afford the glazed plates and cups, didn't handle a lot of coinage and except for church, go near stained glass. They saved themselves from exposure.
Mercury, which could also damage the central nervous system, was used in medicines, including a treatment for leprosy and Rasmussen found mercury in the bones, slightly more in rural settings.
"Lead gets into children's blood stream and in adults, the central nervous system," Rasmussen said. Modern studies have shown damage to the intellectual development of children, he said.
Lead has always been quietly poisoning people throughout history. In ancient Rome, people sweetened bitter wine using a substance called Sugar of Lead, an artificial sweetener. They also used sheets of lead to line the aqueducts. It had to have had some effect on the Romans although it is not possible to trace.
During some periods, lead was used in cosmetics. England's Queen Elizabeth I survived a bout of smallpox that left her face pockmarked. She wore a heavy white facial cream containing lead to hide the scars. Women in the French court at Versailles, over 200 years later, still were.
"The lead would be ingested through the skin just like food," said George Milner, professor of archaeology at Pennsylvania State University in University Park.
In colonial America, water pipes were made of lead, also poisoning drinkers, said Milner.
In more modern times, lead in paint and other sources has caused immeasurable harm, especially for children. Lead was removed from gasoline in the U.S. in 1986.
Rasmussen said he was struck by the different lead levels among the medieval people, with far more lead in the bones of urban folk than rural people.
Milner said the value of research like Rasmussen's is that it provides an idea of what preindustrial environments looked like, a look into what people's private lives were like.
Whether lead poisoning contributed to the Dark Ages being dark, with lead damaging the intellects of the people living there, is unknowable, both Rasmussen and Milner said.
None the people Rasmussen studied died of lead poisoning. There was not enough lead to kill anyone and it was absorbed over many years.
Lead was pervasive, but probably not pervasive enough to affect society, he said.