Pompeii’s public baths were unhygienic until the Romans took over

Going to the public baths of Pompeii meant bathing in water contaminated by sweat and urine – until the Romans took over and sanitary conditions improved.

It’s easy to think of ancient Pompeii as a typical Roman city, especially since it lies only about 150 miles southeast of Rome itself. But for much of its history, Pompeii was occupied by the Samnite people, who had a distinct culture. It was not until after 80 BC that it became a Roman colony, just 160 years before the city was buried in volcanic ash during the eruption of nearby Vesuvius.

However, like the Romans, the Samnites seem to have enjoyed bathing. They built at least two public baths – now known as the Stabian Baths and the Republican Baths – shortly after 130 BC.

Gül Sürmelihindi, from the University of Mainz in Germany, and colleagues analyzed mineral deposits in public baths to get a clearer picture of the quality of the water that once filled their pools.

It turns out the water quality could have been better. “The water from the Republican Baths hot pool had low stable carbon isotope values, indicating the presence of abundant organic matter,” explains Sürmelihindi.

Importantly, when researchers analyzed the mineral deposits in the 40-meter-deep wells that fed the pools, they found few traces of organic matter. “This means that the contamination must have taken place in the swimming pools,” says Sürmelihindi – almost certainly from sweat, oily sebum produced by the skin and even urine left behind by bathers.

There’s probably a good reason for this, researchers say. Extracting water from deep wells using a bucket system was slow and laborious work, and they estimate that only between 900 and 5,000 liters could have been drawn each hour. This was enough to replenish the bath water once or twice a day.

But things changed under Roman rule. Within a few decades, the Romans had built an aqueduct to supply Pompeii with water from natural springs located about 35 km northeast of the city. “We have the impression that building an aqueduct was a priority, but also a question of prestige: if one city had one, the other would want one too,” explains Sürmelihindi.

Researchers estimate that the aqueduct provided Pompeii with 167,000 liters of water per hour – enough to replenish the public baths much more frequently and to provide Pompeii’s residents with a new, convenient supply of drinking water.

Consistent with the idea that public baths became more hygienic, Sürmelihindi and colleagues found that mineral deposits in the drains of Roman-era Stabian baths contained significantly less organic carbon, suggesting that sweat and urine in the water were present at a much lower level due to more frequent replenishment of the pools.

However, this does not necessarily mean that the Pompeians enjoyed a health boost from the new aqueduct. Before its construction, most people drank rainwater collected in cisterns connected to the roofs of buildings in the city. Subsequently, many obtained their drinking water from the aqueduct via a network of lead pipes that ran through the city. Lead, a poison that can damage the brain, could then escape from the pipes and end up in the water.

The contamination should have diminished over time, because mineral deposits eventually coat the inside of the pipes, so the water is no longer in contact with the lead. But some researchers suspect that every time sections of the city’s plumbing are repaired with new pipes, lead contamination would increase again.

“Pompeii’s elite were probably better off, since they lived in houses with large atria and inward-sloping roofs that channeled rainwater into a cistern,” says Duncan Keenan-Jones of the University of Manchester, UK. “The poor who lived in their stores relied more on lead-contaminated water from streetside fountains.”

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