Lead poisoning isn't just a problem for post-industrial city kids — the children of samurai suffered from it too, a new study suggests. An analysis of bones of children who lived as many as 400 years ago showed sky-high lead levels, which scientists now think came from their mothers' makeup.

During the Edo period, from 1603 to 1867, Japan was ruled by a series of shoguns. Below the shogun, a few hundred feudal lords presided over the country's agricultural domains, each from within a castle-town headquarters that was protected by a cadre of samurai military nobles.

At the castle town of Kokura, in the modern city of Kitakyushu, samurai and their families were buried in large clay pots at a local Zen Buddhist temple. A team lead by Tamiji Nakashima, an anatomist at the University of Occupational and Environmental Health in Kitakyushu, studied the remains of 70 samurai men, their wives and children. The researchers sampled the lead in rib bones, and X-rayed some of the children's long arm and leg bones looking for signs of lead poisoning.

What they found surprised them: kids with enough lead in their systems to cause severe intellectual impairment. Children under age 3 were the worst off, with a median level of 1,241 micrograms of lead per gram of dry bone. That's more than 120 times the level thought to cause neurological and behavioral problems today and as much as 50 times higher than levels the team found in samurai adults. Older kids' levels were lower, but still very high.

What's more, five of the children had unusual bone enlargements, and X-rays revealed banding that only turns up in children with at least 70 micrograms of lead per deciliter of blood.

Scientists now understand that blood-lead levels of just 10 micrograms per deciliter can cause "lowered intelligence, reading and learning disabilities, impaired hearing, reduced attention span, hyperactivity, and antisocial behavior," according to an Environmental Protection Agency website. And harmful effects have been noted at even lower levels.

Poison powder

Where might the samurai children have encountered enough lead to cause such extraordinary contamination? Globally, lead contamination is known to be much higher since the industrial revolution than at any other time in history, and Edo-period environmental levels were generally low, as were levels in Kokura.

In this and previous studies, Nakashima and colleagues showed that samurai women had higher lead levels in their bones than samurai men did, and the researchers' suspicions settled on the women's cosmetics. A lead-based white face powder was fashionable among the elite during the Edo period, introduced by celebrity geisha, courtesans and Kabuki actors.

The youngest children most likely picked lead up while nursing, Nakashima and his colleagues surmise. Little did the samurai mamas know, their quest for beauty may have stunted their babes' development. Judging by the ones who didn't make it to adulthood, the authors suggest that many surviving samurai children during the Edo period probably suffered from severe intellectual impairment.

And there's reason to believe lead poisoning may have been widespread among elites: Nakashima and colleagues showed in an earlier study that samurai and merchants living in Kokura had much higher lead levels in their bones than did farmers and fishermen living nearby. They also point to individual shoguns known to have suffered from intellectual and health problems associated with lead poisoning.

"We assume that facial cosmetics were one of the main sources of lead exposure among the samurai class because they were luxuries at that time," Nakashima explained in an e-mail. "The lower class people (farmers and fishermen) did not have the luxury of using cosmetics and the laws strictly prohibited [them] from using cosmetics because they were workers."

Political effects

Nakashima and his team think a ruling class addled by lead poisoning may have contributed to political instability, and ultimately to the collapse of the seven-century-old shogun system in 1867, when power shifted cataclysmically from the shogun to the emperor, and life in Japan changed for good.

It wouldn't be the first time lead poisoning rang in the end of an era. Others have suggested that "plumbism" among the Roman elite — whose fancy food and wine was laced with lead leached from cooking equipment — contributed to the fall of the Roman Empire.

The new research will be published in a forthcoming issue of the Journal of Archaeological Science.