Visiting the public baths in Pompeii meant immersing in water that was often contaminated with sweat and urine, until Roman innovations in sanitation improved the experience.

Commonly perceived as a quintessential Roman city due to its proximity—about 240 kilometers southeast of Rome—Pompeii was predominantly inhabited by the Samnites for much of its history. It fell under Roman control after 80 BC, just 160 years before the catastrophic eruption of Mount Vesuvius buried the city in volcanic ash.

Much like the Romans, the Samnites valued bathing and constructed at least two public baths—the Stavian Baths and the Republican Baths—after 130 BC.

Dr. Gul Surmelihindi and a team from the University of Mainz analyzed mineral deposits within these ancient baths to better understand their water quality.

Interestingly, the water quality was subpar. “The water in the heated pool at the Republican Baths shows low stable carbon isotope values, indicating a high level of organic matter,” stated Surmelihindi.

Crucially, when examining deposits in the 40-meter-deep well supplying water to the pool, researchers found minimal organic matter. “This suggests that contamination likely happened within the pool itself, probably from sweat, oily skin secretions, or urine from bathers,” explains Surmelihindi.

Time and convenience were significant factors; drawing water from wells manually was labor-intensive, yielding only 900 to 5,000 liters per hour—sufficient to refill the baths once or twice daily.

The landscape changed dramatically under Roman rule. Within decades, an aqueduct was constructed to transport water from a natural spring about 35 km northeast of Pompeii. “Building an aqueduct symbolizes both prestige and priority; if one city has one, others will follow,” Surmelihindi remarked.

Researchers estimate that Pompeii’s aqueduct was capable of supplying 167,000 liters of water each hour, allowing for much more frequent refills of the public baths and providing residents with a new, reliable source of drinking water.

This shift led to increased hygiene in the public baths, as shown by the significantly lower amounts of organic carbon found in the drain deposits of the Roman Stavian baths, indicating a reduced concentration of sweat and urine due to more frequent refills.

However, improved water infrastructure did not automatically guarantee public health. Prior to the aqueduct’s construction, many residents relied on rainwater collected from rooftops. Subsequently, drinking water was sourced from the aqueduct via a network of lead pipes. Lead can cause serious health issues, including brain damage according to the World Health Organization.

While mineral deposits over time could reduce lead contamination, researchers caution that each time a section of the city’s pipes is repaired, lead contamination could spike again.

“Pompeii’s elite likely enjoyed access to cleaner water due to their residences, which featured large atriums and roofs designed to collect rainwater in cisterns,” explains Duncan Keenan-Jones from the University of Manchester, UK. In contrast, poorer residents, potentially living above shops, depended on lead-contaminated water from public fountains.

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