Romans regularly soaked in filthy, lead-contaminated bath water, Pompeii study finds

The ancient Romans are well known for their advanced water supply systems and hygienic facilities, including public baths and toilets. But the first baths built in Pompeii may not have been particularly pleasant, due to dirty, contaminated water that was replaced only once per day, according to a new study.

"It is very likely that the bathing experience in this small bathing facility was maybe not hygienic and hence not very inviting," study lead author Gül Sürmelihindi, a geoarchaeologist at the Johannes Gutenberg University of Mainz in Germany, told Live Science in an email.

Sürmelihindi and colleagues analyzed the chemical compound calcium carbonate preserved in incrustations in the Republican Baths at Pompeii to investigate the composition of the water supply. Their study was published Monday (Jan. 12) in the journal PNAS.

Public baths were a key part of Roman culture, the researchers wrote in the study, and as the Roman Empire expanded, bathing culture also evolved. At the height of the Roman Empire, the Romans "built long-distance aqueducts in order to have their daily bathing and cleansing experience," Sürmelihindi said.

But in the earliest baths built at Pompeii, which were in use between about 130 and 30 B.C. during the Roman Republic, the situation was different. Before the city constructed an aqueduct, bathing facilities were filled with water from wells and cisterns via a single water-lifting machine that was operated by enslaved people.

"The water could not be replenished more than once a day," Sürmelihindi said. "In this setting, I would expect water to be less clean, especially before the bathing water was refreshed again."

To investigate the composition of the bath water during this time, the researchers studied samples of calcium carbonate, a mineral form of calcium. Calcium carbonate is produced when calcium ions in hard water react with carbonate ions, leading to limescale — a hard, chalky deposit that builds up in kettles, boilers and pipes.

The researchers found that the carbonate in the Republican Baths showed a strong decrease in carbon isotopes (variations of the element with different numbers of neutrons) between the well that supplied the water and the heated pools where people bathed. The lowest carbon isotope values were found in areas where the water drained, meaning the main cause was likely "the introduction of organic carbon from microbial activity and human waste (e.g., sweat, sebum, urine, bathing oil)," the researchers wrote.

"These baths were an experience we do not have nowadays," study co-author Cees Passchier, a geoarchaeologist at the Johannes Gutenberg University of Mainz, told Live Science in an email. "People would not use soap, but olive oil to rub in and scrape the dirt off, and some of that oil would land in the water."

The water in the heated pools of the Republican Baths shows "high contamination by human waste," suggesting that it was not replenished regularly and that it offered "poor hygienic conditions for the Pompeiian bathers," the researchers wrote.

The researchers also investigated heavy-metal contamination in the baths by analyzing traces of elements left there. In the Republican Baths, the team identified elevated levels of lead, a toxic element that was likely introduced through the lead-pipe system in the bathing complex. Over time, though, the gradual incrustation of the pipes with calcium carbonate would have reduced the water's lead level.

It's unclear whether the murky water would have kept people away.

"Everyone mixed in the baths, regardless of social class, and the price was low," Passchier said. But if the water was really gross and smelly, he said, the baths would not have had customers. "People probably did not spend much time in the warm pools, which were small, but mostly spent time sitting around in the warm air of the hot bath having a conversation," he said.

Pompeii quiz: How much do you know about the Roman town destroyed by Mount Vesuvius?